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ANALYTICAL PYROLYSIS OF COAL DEVELOPMENr OF A THERMAL DEGRADATION PROFILE

S.A. Liebman, C . Wi t te rson , W.A. Bowe, E. J. Levy Chemical Data Systems, I n c . Box 74 Oxford, PA 19363

The cha l lenge t o o b t a i n comprehensive a n a l y t i c a l in format ion on f o s s i l f u e l s has l e d t o t h e development of advanced methods i n a n a l y t i c a l py ro lys i s . Extent ion of m a t e r i a l s c i ence c h a r a c t e r i z a t i o n techniques t o coa l and s h a l e s has permi t ted composi t ional d a t a (e lemental and s t r u c t u r a l ) t o be obtained on t h e s o l i d and generated v o l a t i l e s . has been s u c c e s s f u l l y appl ied i n both m a t e r i a l s c i ences (1) and f o s s i l 6 u e l s t u d i e s (2-4) wi th emphasis on t h e s imula t ion of process cond i t ions coupled t o on- l ine gas chromatographic (GC) a n a l y s i s . Ana ly t i ca l p y r o l y s i s coupled wi th advanced concen t r a to r technology is now app l i ed t o f o s s i l f u e l s t o provide a more complete range of in format ion i n a c o s t - e f f e c t i v e manner.

CDS ins t rumen ta t ion

Development of a thermal degrada t ion p r o f i l e involves a p p l i c a t i o n of con t ro l l ed thermal inpi i ts under i n e r t and r e a c t i v e atmospheres w i t h i n t h e range of r e a l i s t i c process condi t ions . Experimental des ign f o r t h e c o a l and s h a l e s has u t i l i z e d t h e Pyroprobe 123 system coupled t o a modern GC u n i t w i th c a p i l l a r y column c a p a b i l i t i e s . Evolved v o l a t i l e s a r e produced from e i t h e r pulsed py ro lys i s o r programmed hea t ing throughout chosen temp- e r a t u r e i n t e r v a l s between 100-100O'C. Both i n e r t and r e a c t i v e atmospheres in f luence t h e n a t u r e and amount of evolved v o l a t i l e s . The lat ter a r e t rapped on a concen t r a to r t r a p t h a t is i n t e g r a l t o t h e 123 system; t h e v o l a t i l e s a r e then thermally desorbed a s a sharp p u l s e i n t o t h e GC. S ince these da t a a r e obta ined from weighed (mil l igram) amounts of c o a l s h a l e samples, mass ba lance c a l c u l a t i o n s may be obta ined under t h e f u l l range of imposed the rma l f r eac t ive t rea tments .

F igure 1 shows t h e FID/GC chromatogram of v o l a t i l e s evolved from 5 mg of coa l under an ( a ) ox ida t ive ( a i r ) and (b) i n e r t (helium) atmosphere i n t h e low-temperature range (held a t 275°C f o r 10 minutes) . This a n a l y s i s of t h e v o l a t i l e s i l l u s t r a t e s t h e type of GC p a t t e r n which, when coupled wi th i d e n t i f i c a t i o n and q u a n t i t a t i o n , p rovide t h e needed d e t a i l e d s t r u c t u r a l information. Se lec ted r e fe rence compounds and i n t e r n a l s t anda rd iza t ion procedures a l low s p e c i f i c monitor ing of subs tances and t h e i r f a t e under t h e chosen cond i t ions , i . e . water , entrapped gases , e t c .

I n a d d i t i o n t o t h e low-level thermal process ing of f o s s i l f u e l samples under i n e r t , ox ida t ion , o r r educ t ive atmospheres, h igher tempera tures a t varying rates may be imposed upon t h e samples. I n F igure 2 , p y r o l y s i s pa t t e rns a r e shown from a c o a l sample t r e a t e d a t 60°/min t o 1000°C f o r 32 min. under an (a ) a i r and (b) helium atmosphere. The evolved v o l a t i l e s were co l l ec t ed i n t h e in te rna lyenax t r a p and subsequent ly thermal ly desorbed i n t o t h e c a p i l l a r y GC system u d e r t h e cond i t ions g iven i n Table 1. Other workers have shown t h a t 1-alkene/alkane r a t i o s are c o r r e l a t e d t o process y i e l d s from o i l s h a l e s (5) .

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Previous s t u d i e s i n m a t e r i a l sc iences w i t h complex polymer formu- l a t i o n s for smoke, f lammabi l i ty , and t o x i c i t y s t u d i e s have a l s o shown t h a t o x i d a t i v e thermal t rea tments markedly a l te r t h e genera t ion and r e a c t i o n of polyenyl f r e e - r a d i c a l s i n t h e s o l i d phase ( 6 ) . Cer ta in organic / inorganic m a t r i c e s produce increased cross - l ink ing and char when pyrolyzed under oxi- d a t i v e (combustive) a tmospheres , while increased cha in-sc iss ion and g r e a t e r v o l a t i l i z a t i o n r e s u l t e d from degrada t ion under i n e r t ( p y r o l y t i c ) atmospheres . Conjugated a romat ic s t r u c t u r e s a r e dramat ica l ly a f f e c t e d by t h e s e f a c t o r s .

F u r t h e r s t u d i e s t o c o n t r o l and opt imize t h e thermal degrada t ion pathways of complex organic systems have shown t h a t c e r t a i n inorganic a d d i t i v e s a r e very e f f e c t i v e . The r o l e of t rans i t ion-meta i compounds has been s tudied e x t e n s i v e l y (7) a s smoke suppressant a d d i t i v e s t h a t promote ex tens ive c r o s s - l i n k i n g i n t h e s o l i d phase by a proposed " reduct ive coupl ing" mechanism (7b) . Hence, sc reening of such a d d i t i v e s t o e f f e c t t h e d e s i r e d cha in-sc iss ion and v o l a t i l i z a t i o n is d i r e c t l y accomplished by t h e a n a l y t i c a l p y r o l y s i s method. Thereby, a d d i t i o n of s e l e c t e d inorganics o r organometa l l ics t o t h e c o a l o r s h a l e mat r ix permits op t imiza t ion of degrada t ion pathways i n c o a l g a s i f i c a t i o n , d e n i t r i f i c a t i o n , o r d e s u l f u r i - z a t i o n processes . I l l u s t r a t i o n s w i l l be shown t o demonstrate t h i s r o l e of a n a l y t i c a l p y r o l y s i s .

F i n a l l y , i n concer t wi th t h e d e t a i l e d monitor ing of key products and t h e chromatographic p a t t e r n s as a f u n c t i o n of t h e s e thermal / reac t ive t rea tments , t h e o v e r a l l e lementa l composition of c o a l and s h a l e s i s important d a t a . A unique c a p b i l i t y of CDS ins t rumenta t ion i s shown i n F igure 3 w i t h t h e s imultaneous de te rmina t ion of CHNS content of a t y p i c a l c o a l sample. This a n a l y s i s is accomplished by on-l ine r e a c t i o n GC t o e f f e c t s tandard microchemical conversions of t h e v o l a t i l e s generated from t h e c o a l sample (heated t o 1300'C i n oxygen). With such d a t a , e f f e c t i v e N o r S removal t rea tments may be monitored i n concer t wi th t h e v o l a t i l e composition, s i n c e only a few mi l l ig rams a r e needed f o r t h e s e ana lyses .

In summary, i t can be demonstrated t h a t v a l u a b l e informat ion i s generated i n l a b o r a t o r y s c a l e by s imula t ion and a n a l y s i s of r e a l i s t i c process v a r i a b l e s o f temperature , atmosphere, and c a t a l y t i c a d d i t i v e s . This d a t a should a i d on-going c o a l conversion process technologies a s t h e thermal degradat ion p r o f i l e i s f u r t h e r developed.

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R e f e r e n c e s

1 . S. A. L i e b m a n , C . R. F o l t z . C. I . S a n d e r s , W . E . B e a k e s , T. C . C r e i g h t o n , ACS 172nd N a t . Mtg . , O r g . C o a t i n g s & P l a s t i c s D i v . , S a n F r a n c i s c o , CA Aug. 1 9 7 6 " T h e r m a l D e g r a d a t i o n P r o f i l e of Mater ia l s w i t h S c a l i n g a n d S i m u l a t i o n "

2. C . S. G i a m , R. E . G o o d w i n , P . Y . G i a m , K . F . R i o n , S. G . S m i t h , A n a l . Chem. 49 1540 ( 1 9 7 7 ) " C h a r a c t e r i z a t i o n of L i g n i t e s b y PGC"

3. J . L. G l a j c h , J . A. L u b k o w i t z , J . C h r o m a t . - 1 6 8 , 3 5 5 ( 1 9 7 9 )

4 . B. K . H o v s e p i a n , N . Amer. T h e r m a l A n a l . S O C . , 1 2 ( 1 9 8 0 ) " A n a l . P y r o l y s i s of F o s s i l F u e l s G i n g F l a s h P y r o l y s i s as s S c o u t i n g T e c h n i q u e " .

5. T. T . C o b u r n , R . E . B o z a k , J . E . C l a r k s o n , J. H . C a m p b e l l , A n a l . Chem. , 50 9 5 8 ( 1 9 7 8 ) " C o r r e l a t i o n of S h a l e O i 1 1 - a l k e n e / a l k a n e Rat io w i t h P r o c e s s Y i e l d "

6 . a ) S. A. L i e b m a n , J . F. R e u w e r , K . A . G o l l a t z , C. D . Nauman, J . Po lym. S c i . , P a r t A - 1 , - 9 1 8 2 3 ( 1 9 7 1 ) P a r t I .

b ) S. A. L i e b m a n , D. H . A h l s t r o m , E . J . Q u i n n , A. G . G e i g l e y , J . T. M e l u s k e y , I b i d . 1921 ( 1 9 7 1 ) P a r t 11.

7 . a ) N . J . K r o e n k e , J . Appl. Polym. S c i . , i n press.

b ) R. P. L a t t i m e r , W. J . K r o e n k e , I b i d .

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T a b l e 1 ~-

320 Concent ra tor

S a m p l e : 5 mg coal i n q u a r t z t u b e / c o i l

S a m p l i n g : Desorber P u r g e 1 r n i n . , no h e a t P y r o p r o b e

Desorber Heat 250°C f o r 1 5 m i n . 24" x 1 /8 " OD SS T e n a x T r a p - 2 0 m l / m i n H e ( o r a i r )

I n j e c t i o n : B a c k f l u s h T r a p A a t 6 0 m l / m i n . He ( s p l i t f l o w ) a t 265°C f o r 5 min t o G C

R e c o n d i t i o n : B a c k f l u s h T r a p A a t 2 5 m l / m i n He a t 265°C f o r 1 0 m i n .

P y r o l y s i s

S a m p l i n g : P y r o p r o b e : 1 0 0 0 ° C a t 6 0 " / m i n

Desorber P u r g e 1 m i n , no h e a t D e s o r b e r Heat 250°C f o r 3 2 min,

f o r 3 0 min

20 m l / m i n H e (or a i r ) I n j e c t i o n : A s a b o v e R e c o n d i t i o n : As a b o v e

GC A n a l y s i s - P e r k i n E l m e r , S i g m a 11, FID _ _ _ ~

Column: 2 5 x .21 mm I D f l e x i b l e f u s e d

Oven : 4 0 " C , 2 m i n , t h e n 1 0 " / m i n t o 2 7 5 " C ,

S p l i t flow: 60 m l / m i n H e ; s p l i t r a t i o , 6 0 : 1

Detector: A t t ' n x as n o t e d C h a r t : 1 cm/min

s i l i c a WCOT OV-101

1 0 min

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J Figure 1 - Coal Volatiles Analyzed by Capillary

GC - Thermal Treatment at Low Temp- erature (275°C. 10 min) in (a) air (b) helium

COAL VOLATILES ANALYZED BY CAPILLARY GC

(a) AIR J- / Ir " '

I I 1 0 0 0 ~ ~ at 60°, min (b) HELIUM

/ Figure 2 - Coal Volatiles Analyzed by Capillary

G C - Thermal Treatment at high temperature (100' to 1OOO'C at 60'/rnin) in (a) air (b) helium

ON-LINE SIMULTANEOUS C,H,N,S ANALYSIS OF COAL

I co2

I H20

Figure 3 - On-line, Simultaneous Elemental C, H, N , S, Analysis of coal

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COAL PYROLYSIS AT H I G H TEMPERATURE"

P. R. Solomon and D. G. Hamblen

Advanced F u e l Research , I n c . 87 Church S t r e e t , E a s t H a r t f o r d , CT 06108

and G. J. Goetz and N . Y. Nsakala

K r e i s i n g e r Development Labora tory Combustion E n g i n e e r i n g , I n c . , Windsor , CT 06095

INTRODUCTION

T h i s paper c o n s i d e r s t h e a p p l i c a t i o n of a r e c e n t l y developed p y r o l y s i s model t o t h e h i g h tempera ture r a p i d p y r o l y s i s o f c o a l i n a n e n t r a i n e d f l o w r e a c t o r . The model i s based on exper iments u s i n g a h e a t e d g r i d p y r o l y s i s a p p a r a t u s , which have he lped t o e s t a b l i s h a r e l a t i o n s h i p between t h e chemica l s t r u c t u r e of a c o a l and i t s p y r o l y s i s p r o d u c t s (1-9). The r e l a t i o n s h i p has been i n c o r p o r a t e d i n t o a k i n e t i c model o f thermal decomposi t ion (1-6) which h a s t h e f o l l o w i n g g e n e r a l f e a t u r e s : 1 ) The t ime and tempera ture dependent e v o l u t i o n o f t h e p r o d u c t s of thermal decomposi t ion a r e p r e d i c t e d u s i n g a g e n e r a l s e t o f k i n e t i c parameters and a knowledge o f t h e c o a l ' s s t r u c t u r a l composi t ion ; 2 ) t h e e v o l u t i o n of a s p e c i e s r e s u l t s from t h e thermal decomposi t ion of a p a r t i c u l a r s t r u c t u r a l e lement w i t h i n t h e c o a l a t a k i n e t i c r a t e which depends on t h e t y p e of e lement b u t which i s r e l a t i v e l y i n s e n s i t i v e t o c o a l r a n k ; 3 ) much of t h e needed s t r u c t u r a l i n f o r m a t i o n c a n be o b t a i n e d from q u a n t i t a t i v e F o u r i e r Transform I n f r a r e d (FTIR) a n a l y s i s o f t h e c o a l and p y r o l y s i s products . The model h a s proved s u c c e s s f u l i n s i m u l a t i n g t h e r e s u l t s o f vacuum thermal decomposi t ion e x p e r i m e n t s i n a h e a t e d g r i d f o r a v a r i e t y of b i tuminous c o a l s and l i g n i t e s .

The h e a t e d g r i d e x p e r i m e n t h a s a d v a n t a g e s over o t h e r p y r o l y s i s exper iments i n a c h i e v i n g good mass and e l e m e n t a l b a l a n c e s and i n a l l o w i n g t h e pr imary p y r o l y s i s p r o d u c t s t o be observed w i t h minimal secondary r e a c t i o n s . I t has t h e d i s t i n c t d i s a d v a n t a g e , however, t h a t t h e h e a t i n g of t h e c o a l i s s lower t h a n i n p r a c t i c a l d e v i c e s and i t is v e r y d i f f i c u l t t o measure o r e s t i m a t e t h e t ime- tempera ture h i s t o r y o f t h e c o a l . While t h e g e n e r a l c o n c e p t s of t h e thermal decomposi t ion model and t h e r e l a t i v e magnitude of k i n e t i c ra tes a p p e a r t o be v a l i d , t h e e x a c t k i n e t i c r a t e s e s p e c i a l l y a t h i g h t e m p e r a t u r e s a r e u n c e r t a i n . To improve t h e k i n e t i c d a t a , o t h e r exper iments a r e needed. I n one approach which h a s r e c e n t l y been r e p o r t e d , c o a l i s dropped i n t o a h o t f u r n a c e and t h e e v o l v i n g g a s e s a r e moni tored i n - s i t u w i t h a FTIR (10). T h i s exper iment v e r i f i e d t h e g e n e r a l f e a t u r e s of t h e model b u t y i e l d e d h i g h e r k i n e t i c r a t e s . The exper iment c o u l d o n l y f o l l o w e v e n t s on a time s c a l e l o n g e r t h a n a few hundred m i l l i s e c o n d s due t o t h e l i m i t imposed by t h e FTIR s c a n n i n g r a t e . Data w a s p r e s e n t e d f o r t e m p e r a t u r e s between 500" and 800" C .

I n t h e p r e s e n t i n v e s t i g a t i o n , r e s u l t s a r e ex tended t o t e m p e r a t u r e s up t o 1470" C and h i g h e r r a t e s u s i n g p y r o l y s i s e x p e r i m e n t s performed i n a n e n t r a i n e d f low r e a c t o r a t Combustion Engineer ing . I n t h i s exper iment c o a l i s i n j e c t e d i n t o a h o t gas s t r e a m and a f t e r a v a r i a b l e r e s i d e n c e t i m e o f 0 t o 450 m i l l i s e c o n d s , t h e r e a c t i o n i s quenched. The p y r o l y s i s gas composi t ions were de te rmined and t h e c h a r s were a n a l y z e d by FTIR, e l e m e n t a l a n a l y s i s and o p t i c a l microscopy t o d e t e r m i n e t h e changes i n c h a r c h e m i s t r y and p h y s i c a l appearance . The t ime- tempera ture h i s t o r i e s o f t h e s o l i d p a r t i c l e s h a v e b e e n c a l c u l a t e d t o provide i n p u t t o t h e p y r o l y s i s model. p y r o l y s i s model was s u c c e s s f u l i n s i m u l a t i n g t h e r e a c t o r d a t a a f t e r ad jus tment t o t h e k i n e t i c r a t e s a t h i g h t e m p e r a t u r e s .

The

-- ---- *Work suppor ted under EPRI c o n t r a c t s RP1654-6 and RP1654-7

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EXPERIMENTAL

Combustion Engineering's Drop Tube Furnace System (DTFS) is similar in design to the reactors described by Nsakala et. al. (11) and Badzioch and Hawksley (12). The DTFS (Fig. 1) is comprised of a 2.54 cm inner diameter preheater, a 5.08 cm inner diameter test furnace, a fuel feeding system, and a gas analysis system. furnaces are powered with silicon carbide (Sic) heating elements.

The conditions of this particular experiment were as follows follows: 1) A 200 x 400 mesh size fraction of Pittsburgh seam coal was introduced by screw feeding through a water-cooled probe into the test furnace reaction zone; 2) The primary stream (comprised of the fuel fed at a rate of 1 gram/min and 15% C02/85% N2 carrier gas fed at 2 liters/min) was allowed to mix rapidly with a preheated down-flowing secondary gas (15% CO /85% N ) stream (fed at 28 liters/min); 3) After a variable distance (zero to 40.8 cm) tge pyrolysis products were aspirated in a water-cooled probe to quench all the reactions; 4) The solids were separated from gaseous products in a small cyclone; 5 ) A portion of the gas sample was analyzed on-line to determine NO , concentrations; and 6 ) Solid samples were

performed with furnace wall temperatures of 1370 and 1470°C. Free fall velocities of particles in these experiments were small compared with gas velocities; hence it was assumed that the particles traveled at the same velocities as the gas. Maximum residence times in the reaction zone varied from 0.342 to 0.453 sec for the higher and lower temperature, respectively.

Both

CO, C02 and SO analyzed by FTIiT'ultimate analysis 2 and optical microscopy. Experiments were

PYROLYSIS RESULTS

The physical and chemical changes occurring during pyrolysis are characterized by the data illustrated in Figs. 2, 3, 5 and 6 . Figure 2 follows the infrared spectra of solid samples collected at various positions in the reactor. The techniques for preparing and analyzing the FTIR spectra have been presented previously (2). figure presents the absorbance from 1 mg of sample in a KBr pellet or 1 mg/1.33 cm2. The data are for a wall temperature of 1370°C. The results indicate that no changes occur for the first 5 cm in the reac or. Between 5 and 10 cm the absorbance in the aliphatic stretch region at 2900 cm-' decreases, indicating a decreasing concentration of aliphatic C-H bonds wh'ch goes to zero at 20 cm. The behavior of the aromatic stretch region at 3050 cm-* indicates that the aromatic C-H concentration starts to decrease between 10 and 20 cm. The behavior of the region near 1200 cm-l indicates that the density of 0-C bonds is not decreased during the initial stage of pyrolysis. The FTIR spectra for the 1470'C wall temperature are similar except that the aliphatic C-H concentration goes to zero at 10 cm and the aromatic C-H concentration at 10 cm is about the same as it is for 20 cm in the lower temperature run.

The samples were examined optically to determine physical change occurring during pyrolysis. In agreement with the FTIR results, little happens to the samples collected at 5 cm or less. At 10 cm however, the particles are observed to have become substantially swollen. By 20 cm they are well formed structures which look like foamy soap bubbles. The wall thickness in these bubbles appears to be about 1 micron. slightly. Results for the 1370°C run showing samples collected at zero and 20 cm are presented in Fig. 3. The long dimension of the photomicrograph is 1.9 mm. The swelling increases the diameter by a factor of about 4.

The

At 30 and 40 cm the bubbles appear to be more opaque and have shrunk

CALCULATION OF TIME-TEMPERATURE HISTORIES

Calculations were made of the following quantities: 1) the average gas temperatures in the preheater, the experimental section and the collection probe; 2) the radially dependent gas temperature in the experimental section; 3) the coal particle temperatures and 4) the temperature of a thermocouple at positions along the reactor

7

c e n t e r l i n e . The c a l c u l a t i o n s i n c l u d e a model f o r t h e p a r t i c l e s w e l l i n g which i s found t o produce a r a p i d t e m p e r a t u r e r i s e because of t h e i n c r e a s e i n s u r f a c e a r e a f o r a b s o r b i n g r a d i a t i o n .

To d e t e r m i n e b o t h r a d i a l and l o n g i t u d i n a l tempera ture p r o f i l e s , c a l c u l a t i o n s were performed n u m e r i c a l l y on a PDP/11 computer by c o n s i d e r i n g t u b u l a r s h e l l s a t p r o g r e s s i v e c r o s s s e c t i o n s of t h e f low p a t h . The r a d i a l gas t e m p e r a t u r e s a r e c a l c u l a t e d f o r t h e p r i m a r y g a s c o r e , and f o r n c o n c e n t r i c r i n g s o f g a s . The t o t a l c a l c u l a t i o n proceeds a s f o l l o w s : s t a r t i n g a t t h e i n l e t , w i t h t h e p a r t i c l e tempera ture set e q u a l t o t h e pr imary g a s t e m p e r a t u r e , n-1 c o n c e n t r i c g a s r i n g s set e q u a l t o t h e s e c o n d a r y g a s t e m p e r a t u r e , and t h e o u t e r r i n g f i x e d a t t h e w a l l t e m p e r a t u r e , a sys tem of d i f f e r e n t i a l e q u a t i o n s a r e i n t e g r a t e d u s i n g a Runga-Kutta i n t e g r a t i o n scheme to d e t e r m i n e t h e tempera ture o f each element a t t h e n e x t t i m e increment . (Note-The d i f f e r e n t i a l e q u a t i o n s i n c l u d e : a ) r a d i a t i v e h e a t t r a n s f e r between t h e c o a l p a r t i c l e s and t h e w a l l i n c l u d i n g t h e e f f e c t s of t h e c o l d i n j e c t o r and c o l l e c t o r ; b ) c o n v e c t i v e h e a t t r a n s f e r between t h e c o a l and t h e c o r e g a s c ) c o n d u c t i v e h e a t t r a n s f e r w i t h i n t h e g a s ; and d ) t h e h e a t c a p a c i t i e s of t h e c o a l and g a s ) . Using t h e s e new t e m p e r a t u r e s , an a v e r a g e t e m p e r a t u r e f o r t h e gas i s c a l c u l a t e d ( t h e t e m p e r a t u r e a f t e r complete m i x i n g ) , and t h i s average tempera ture i s used t o c a l c u l a t e an a v e r a g e v e l o c i t y , which i n t u r n i s used t o c a l c u l a t e t h e a x i a l p o s i t i o n of t h e p a r t i c l e s and t h e g a s . compared wi th s t a n d a r d p r e d i c t i o n s f o r h e a t t r a n s f e r i n a p i p e ( 1 3 ) and i t was found t h a t under t h e p a r t i c u l a r c o n d i t i o n s of t h e exper iment t h e a d d i t i o n a l h e a t t r a n s f e r due t o c o n v e c t i o n and t u r b u l e n c e (even i n t h e c o l l e c t i o n t u b e ) could be n e g l e c t e d . The g e n e r a l c o n c l u s i o n from t h e s e c a l c u l a t i o n s i s t h a t t h e p a r t i c l e tempera ture i s dominated by r a d i a t i o n from t h e h o t f u r n a c e w a l l s . The p a r t i c l e s h e a t r a p i d l y and a c h i e v e t e m p e r a t u r e s c l o s e t o t h e w a l l t e m p e r a t u r e s . The l o c a l g a s around the p a r t i c l e s ( e . g . t h e p r i m a r y g a s s t r e a m ) i s h e a t e d by c o n d u c t i o n from t h e p a r t i c l e s b u t t h e secondary gas s t r e a m i s n o t w e l l coupled t o t h e p a r t i c l e s . For t h i s r e a s o n mixing e f f e c t s a p p e a r e d t o be of minor impor tance f o r c a l c u l a t i n g p a r t i c l e t e m p e r a t u r e s i n t h e r e a c t o r s e c t i o n .

The r e s u l t s o f t h e c a l c u l a t i o n f o r t h e c o l l e c t i o n probe a t 5 and 10 cm are shown i n F ig . 4 . For t h e 5 cm c a s e t h e p a r t i c l e t e m p e r a t u r e r i s e s r a p i d l y , d r i v e n by r a d i a t i v e h e a t i n g . The pr imary gas tempera ture a l s o r i ses r a p i d l y (much f a s t e r than i n t h e absence of t h e c o a l ) due t o h e a t t r a n s f e r from t h e c o a l . The average g a s tempera ture is dominated by t h e secondary g a s which i s n o t w e l l coupled t o t h e c o a l p a r t i c l e s and t h u s h e a t s a s i n t h e c a s e f o r no c o a l . The tempera ture f o r t h e c o a l and t h e gas i s assumed t o f a l l i n t h e s m a l l e r d i a m e t e r c o l l e c t i o n probe a t a un i form tempera ture due t o t u r b u l e n t mixing. To c o o l below r e a c t i o n t e m p e r a t u r e s t a k e s about 20 m i l l i s e c o n d s .

The p a r t i c l e volume i s assumed t o i n c r e a s e wi th t h e volume of evolved g a s e s u n t i l i t h a s reached f o u r t imes i t s o r i g i n a l d i a m e t e r , which appeared t o b e t h e e x p e r i m e n t a l l y o b s e r v e d l i m i t . According t o t h e p r e d i c t i o n a t t h e 5 cm c o l l e c t i o n p o i n t t h e p a r t i c l e d i a m e t e r s t a r t s t o change s l i g h t l y f o r t h e h i g h e r w a l l t e m p e r a t u r e exper iment b u t n o t f o r t h e lower w a l l t empera ture . The v o l a t i l e y i e l d c o r r e s p o n d i n g t o t h i s change would b e less than 1%. These r e s u l t s a r e i n agreement w i t h t h e chemical and FTIR measurements of t h e samples f o r 5 cm and l e s s which show no measurable change from t h e raw c o a l and w i t h t h e v i s u a l o b s e r v a t i o n of t h e 5 cm sample which shows some s l i g h t p a r t i c l e s w e l l i n g f o r s m a l l p a r t i c l e s i n t h e h i g h t e m p e r a t u r e w a l l c a s e .

By 1 0 c m t h e c o a l f o r b o t h w a l l t e m p e r a t u r e s has come t o w i t h i n 100 k e l v i n s of t h e w a l l t e m p e r a t u r e . The c o a l t e m p e r a t u r e exceeds t h e a v e r a g e g a s t e m p e r a t u r e because of t h e b e t t e r r a d i a t i o n c o u p l i n g t o t h e w a l l . The p a r t i c l e s w e l l i n g i s comple te f o r b o t h w a l l t e m p e r a t u r e s i n agreement wi th t h e v i s u a l o b s e r v a t i o n o f t h e samples f o r 1 0 c m and g r e a t e r .

The r e s u l t s o f t h e c a l c u l a t i o n s were

8

PYROLYSIS MODEL

The pyrolysis model assumes a coal structure consisting of highly substituted aromatic ring clusters containing heteroatoms linked by relatively weak aliphatic bridges. break, releasing the clusters and attached bridge fragment which comprise the tar. Simultaneous with the evolution of tar molecules is the competitive cracking of bridge fragments, substituted groups and ring clusters to form the light molecular species of the gas. The quantity of each gas species depends on the functional group distribution in the original coal. At low temperatures there is very little rearrangement of the aromatic ring structure. There is, however, decomposition of the substituted groups and aliphatic (or hydroaromatic) structures resulting in C02 release from the carboxyl, H20 from hydroxyl, hydrocarbon gases from aliphatics, H2S from mercaptans and some HCN and CO from weakly bound nitrogen and oxygen groups. At high temperature there is breaking and rearrangement of the aromatic rings. this process, H2 is released from the aromatic hydrogen, CS2 from the thiophenes, HCN from ring nitrogen and additional CO from tightly bound ether linkages. process continues the char becomes more graphitic.

A striking feature of thermal decomposition which was observed for a variety of coals is that the temperature dependent evolution rate of a particular species is similar for all coals. This is true even though the amount of the species may vary substantially from one coal to another. These rates characterize the thermal decomposition of the various functional groups. They depend on the nature of the functional group but appear insensitive to coal rank. may be attributed to differences in the mix of functional groups.

The mathematical description of the pyrolysis model has been presented previously ( 1 - 6 ) . The evolution of tar and light species provide two different mechanisms for removal of a functional group from the coal; evolution as a part of a tar molecule and evolution as a distinct species with cracking of the molecule. To model these two paths with one path yielding a product which is similar in composition to the parent coal, the coal is represented as a rectangular area with X and Y dimensions. The Y dimension is divided into fractions according to the chemical composition of the coal. Yoi represents the initial fraction of a particular component (carboxyl, aromatic hydrogen, etc) and zYoi=l. The evolution of each component into the gas (carboxyl into C02, aromatic hydrogen into H2, etc) is represented by the first order diminishing of the Y. dimension, Yi=Yoi exp(-kit). into a potential tar formikg fraction Xo and a non-tar forming fraction 1-Xo with the evolution of the tar being represented by the first order diminishing of the X dimension X=X" exp(-ktt). (l-Xo+X)Y. and the amounts in the gas and tar may be obtained by integration. In the heited grid experiment the products cool upon evolution so they undergo no further reactions. In the present experiment, the evolved products continue to react. Under these conditions it has been assumed that the decomposition of a component occurs at the same rate in the evolved product as it does in the char.

The coal compositional parameters for the Pittsburgh seam coal and the kinetic rates used in the simulation are presented in Table I. Most of the composition parameters have been obtained from elemental and FTIR analysis. The carboxyl, CO-loose and N-loose have been estimated from the parameters of a previously run Pittsburgh seam coal (5) by assuming that these components represented the same fraction of the oxygen and nitrogen in both coals. groups conforms to the experimental observation that these components have at least two distinct evolution rates which presumably indicate distinct chemical species. The tar was estimated from the previously measured coal, but decreased by 30% to

Evidence suggests that during thermal decomposition these weak links

In

As this

The differences between coals

The X dimension is divided

The amount of a particular component in the char is

The split of the N and CO into loose and tight

9

account for the decrease in going from vacuum to 1 atmosphere (see Ref. 9). The kinetic rates have been modified from those most recently presented (5). and CO-tight rates have been increased at high temperature to match the new experimental data. 2 ) The rates for the other species appeared to be adequate at high temperature. However, the recent experiments by Freihaut et a1 (10) suggest that they are low in the range 500-800°C. between these observations and the heated grid data. 3) The rates have also been simplified by using the same rate for tar, N-loose, CO-loose, carboxyl and hydroxyl instead of 5 slightly different rates.

RESULTS

The theory and experiment are compared in Figs. 5 and 6 for the two temperatures (1370°C and 1470'C) which were measured. Fig. 5a and 5b illustrate the char composition. The model predicts that little happens for the first 5 cm for both temperatures. At 10 cm and longer there are substantial changes especially in the hydrogen and oxygen. The model predicts a rapid decrease in the aliphatic hydrogen followed by a slower decrease in the aromatic hydrogen. This behavior is confirmed by the FTIR spectra. The model prediction for oxygen indicates an initial rapid evolution of CO , H20 and CO-loose and a slower evolution of CO-tight from ether groups. The FTfR spectra (Fig. 2 ) show a rapid decrease in the OH co centration indicated by the decrease in the broad peak between 3600 and 2200 cm-' and the sharp peak at 1600 cm-l which is attributed to an aromatic ring stretch enhanced by attached hydroxyl groups (2 ) . the persistence of a narrower KBr-H20 peak at 3400 cm- . less sample is used for the high carbon content chars so that scaling the spectra to 1 mg/1.33 cm2 enhances the contribution from the KBr.) decreases, the CO concentration increases in agreement with the data in Figs. 5c, and 5d. These predictions do not inclue secondary gas-char reactions.

Figures 6a and 6b show predictions f o r f o u r additional evolved species. The stable products from the evolution of the hydrocarbons are H and soot. This was observed in the heated grid experiments (3,5). short lived due to thermal cracking to soot and hydrogen.

Figures 6c and 6d show the overall product distribution. are obtained using the ash tracer method (14). Unfortunately, soot may be included in varying amounts with the char. This would tend to underestimate the char concentration by a varying amount.

CONCLUSION

A pyrolysis model which was developed to simulate coal pyrolysis in a heated grid appears to be successful in simulating the high temperature pyrolysis of coal in an entrained flow reactor. The model relates evolved products to the coal structure. The structure parameters for the coal were input on the basis of the parameters obtained for a similar coal in the heated grid. No adjustments of these structure parameters were made in making the simulation. modifications of the parameters derived from the heated grid experiments. changes were made in the aromatic hydrogen and CO-tight rates at high temperatures. The exponential and preexponential factors for these two components were adjusted to increase the rate in the range 137O-147O0C but hold its value close to the original rates at lower temperature s o that a fit is still obtained for the heated grid data.

The rates for aliphatics, tar, hydroxyl, CO-loose, N-loose and carboxyl received minor adjustments and so still fit the heated grid data.

The rates with the greatest uncertainty are those for olefin, acetylene and soot for which there is no data from the present experiment.

1) The H2

The rates of Table I are a compromise

(Note- The decrease in !he broad band is confused by This occurs because much

A s the char oxygen

Predictions for C02 and H20 produced in pyrolysis are also presented.

The methane an3 acetylene are predicted to be

The experimental points

The kinetic parameters were Major

The soot rate (the rate for

10

conversion of aliphatic to soot) is the highest rate in the simulation. It dominates the initial fast change i n the coal. needed to sort out the effects of the aliphatic evolution and subsequent cracking to olefins, acetylene and soot.

Additional experimental work is

ACKNOWLEDGEMENT

The authors wish to acknowledge the contributions of Dr. Joseph Yerushalmi (formerly of EPRI) and Dr. George Quentin of EPRI who were instrumental in bringing together the experimental and theoretical work.

1.

2.

3.

4.

5.

6 .

7.

8 .

9.

10.

11.

12.

13.

14.

REFERENCES

Solomon, P. R. and Colket, M. B., Fuel, 57, 749, (1978),. Solomon, P. R., ACS Div. of Fuel Chemistry, Preprints, 3, #Z, 184 and Advances in Chemistry, to be published, (1979),.

Solomon, P. R., ACS Div. of Fuel Chemistry Preprints, 3, # 3 , 154, (1979a),.

Solomon, P. R. and Colket, M. B., 17th Symposium (International) on Combustion, P. 131, the Combustion Institute, Pittsburgh, PA, (1979).

Solomon, P. R. and Hamblen, D. G., Understanding Coal Using Thermal Decomposition and Fourier Transform Infrared Spectroscopy, Presented at the Conference on the Chemistry and Physics of Coal Utilization, Morgantown, West Virginia, June 2-4, (1980) . Solomon, P. R., Fuel, 60, 3, (1981),. Suuberg, E. M. et al, Ind. Eng. Chem. Process Design Develop. 17,37, (1978),.

Suuberg, E. M., Peters, W. A. and Howard, J. B., Seventeenth Symposium (International) on Combustion, p. 117, The Combustion Institute, Pittsburgh, PA, (1979).

Suuberg, E. M., Peters, W. A . and Howard, J . B., Am. Chem. SOC. Dir. Petrol. Chem. Preprints, 2, (l), 175, (1977).

Freihaut, J. D., Solomon, P. R. and Seery, D. J., ACS, Division of Fuel Chemistry Preprints, 21, Sept., (1980).

Nsakala, N..Y., Essenhigh, R. H. and Walker, P. L . , Jr., Combustion Sci. Technol., E, 153, (1977).

Badzioch, S. and Hawksley, P. G., W. Ind. Eng. Chem. Process Des. Dev., - 9, 521, (1970).

Heat Transfer, Alan J. Chapman, Macmillan Publish. Co., (1980).

Kobayashi, H., Howard, J. B. and Sarofim, A. F., Sixteenth Symposium (International) on Combustion, The Combustion Institute, Pittsburgh, PA, 411, (1971).

11

TABLE I

K i n e t i c R a t e s a n d F u n c t i o n a l Group C o m p o s i t i o n f o r a P i t t s b u r g h Seam B i t u m i n o u s

C o m p o s i t i o n P i t t s b u r g h P a r a m e t e r Seam (dmmf) B i t u m i n o u s ~ _ _ _ ~ _ _ _ C H N S ( o r g a n i c ) 0 S ( m i n e r a 1 )

C02 - C a r b o x y l H 0 - 9 / 1 7 H y d r o x y l C 8 - E t h e r L o o s e CO - E t h e r T i g h t N - N i t r o g e n L o o s e N - N i t r o g e n T i g h t C H l S w - A l i p h a t i c H - r o m a t i c H C - Nan V o l a t i l e S - O r g a n i c

T o t a l

T a r O l e f i n s A c e t y l e n e s o o t

.853

.057

.017

.021

.052

.014*

.006

. 0 1 0

.006

.062

. 0 0 3

. 0 1 4

.276

.020

. 5 8 2

.02 1

1 .000

.30

kl = 5400 e x p ( - 8 8 5 0 / T ) k2 = 5400 e x p ( - 8 5 5 0 / T ) k3 = 5400 e x p ( - 8 8 5 0 / T ) K4 = 2.15 x 10'' e x p ( - 5 7 0 0 0 / T ) k5 = 5400 e x p ( - 8 8 5 0 / T ) k 6 = 290 e x p ( - 1 3 0 0 0 / T ) k7 = 19000 e x p ( - 1 1 0 0 0 / T ) K8 = 40644 e x p ( - 1 4 0 8 5 / T ) K9 = 0

K t = 5400 e x p ( - 8 8 5 0 / T ) KO = 2 x 10 Ka = 1 x 10 l6 Ks = 4 x 10 l 9

e x p ( - 2 4 0 0 0 / T ) e x p ( - 5 0 0 0 0 / T ) e x p ( - 6 0 0 0 0 / T )

*Dry

12

0 4

0 '9

0 s.

n

YRVENUMRERS

13

a ) , Char Samples a t 0 cm,

-----I p- 1 mm

b ) , Char Samples a t 20 cm,

FIGURE 3 . PHOTOMICROGRAPHS OF CHAR SAMPLES FROM THE D T F S

14

C O L U C l O R A l 5 m

r e a c t o r c o l l e c t o r

i izm

f

- , Y - 5

Sam

om

TIME HISTORY OF TEMPERATURE AND PARTICLE DIAMETERS I N THE DTFS. p a r t i c l e t e m p e r a t u r e s . t e m p e r a t u r e s and p a r t i c l e d i a m e t e r . The upper c u r v e is f o r a 1744 K w a l l t e m p e r a t u r e and t h e lower c u r v e is f o r 1644 K .

Dashed l i n e s are S o l i d l i n e s a r e t h e pr imary g a s t e m p e r a t u r e s , a v e r a g e g a s

A p a i r o f c u r v e s is p r e s e n t e d f o r e a c h p r o p e r t y ,

15

1

I h

u v

w a P

L.. Ur

16

. . . . , . . . .

. . ----. . . * .

B L

1; e

0 In

0 J

0 m

0 N

0 4

3

1

h

W v

1"1 z $ 0 cv

0 d

17

EVOLUTION OF FUEL NITROGEN DURING THE VACUUM THERMAL DEVOLATILIZATION OF COAL

J . D . F r e i h a u t and D. 3. Seery

United Technologies Research Center E a s t Har t ford , CT 06108

I n t r o d u c t i o n

The f a t e of f u e l n i t r o g e n d u r i n g t h e combustion o r g a s i f i c a t i o n of c o a l is a m a t t e r of p r a c t i c a l and fundamental concern. During c o a l combustion, NO, i s known t o form v i a HCN s p e c i e s r e l e a s e d from t h e n i t rogen-conta in ing molecular components of t h e coa l . During g a s i f i c a t i o n p r o c e s s e s , t h e r e l e a s e of n i t rogen-conta in ing fused r i n g compounds i n evolved t a r s p e c i e s is a m a t t e r of environmental concern. S ince t h e t h e r m a l decomposi t ion of t h e p a r e n t c o a l i s an i n i t i a l phase i n both com- b u s t i o n and g a s i f i c a t i o n , i t i s necessary t o deve lop a knowledge of t h e f a t e o f f u e l n i t r o g e n d u r i n g thermal decomposi t ion.

T h i s s t u d y c o n t a i n s r e s u l t s of an i n v e s t i g a t i o n of t h e e v o l u t i o n of f u e l n i t r o g e n d u r i n g the vacuum thermal decomposi t ion of c o a l . R e s u l t s are shown f o r v a r i a t i o n s w i t h c o a l c h a r a c t e r i s t i c s and apparent thermal h i s t o r y . Apparent h e a t i n g r a t e s of 75 C/sec t o 2000 C/sec and f i n a l tempera tures of 500 C t o 1780 C were u t i l i z e d . A v a r i e t y of c o a l s were i n v e s t i g a t e d ranging i n rank from a l i g n i t e t o an a n t h r a c i t e .

The r e s u l t s i n d i c a t e t h a t n i t r o g e n d i s t r i b u t i o n i n t h e v o l a t i l e s is a s e n s i t i v e f u n c t i o n of t h e chemica l c h a r a c t e r i s t i c s of t h e p a r e n t c o a l . T h i s d i s t r i b u t i o n of n i t r o g e n i n t h e l i g h t g a s , t a r and char p r o d u c t s of vacuum d e v o l a t i l i z e d c o a l is h i g h l y dependent on r a n k of t h e p a r e n t c o a l . V a r i a t i o n s i n n i t r o g e n e v o l u t i o n with c o a l c h a r a c t e r i s t i c s are most r e a d i l y apparent i n s e v e r a l a s p e c t s : (1) t h e c o a l n i t r o g e n r e l e a s e d w i t h t h e t a r s p e c i e s ; (2) t h e release of n i t r o g e n contained i n pr imary t a r s as HCN upon secondary thermal decomposi t ion r e a c t i o n s of t h e pr imary tars; ( 3 ) t h e r e t e n t i o n of n i t r o g e n i n t h e char s p e c i e s .

Experiment a1 Design

Figure 1 r e p r e s e n t s s c h e m a t i c a l l y t h e a p p a r a t u s employed t o perform t h e thermal decomposi t ion exper iments . The procedure i n v o l v e s p i a c i n g s m a l l samples (20-50 mg) of f i n e l y ground c o a l (-100+325 mesh) between t h e f o l d s of a f i n e mesh s c r e e n .

18

S t a i n l e s s s t e e l i s used f o r f i n a l t empera tures between 500 C and 1000 C. Tungsten i s used f o r tempera tures between 1000 C and 1780 C. determined tempera ture v i a t h e p r e s e t c o n t r o l c i r c u i t r y . is monitored by a thermocouple bead placed between t h e f o l d s of t h e screen .

The g r i d is d r i v e n t o a pre- The apparent h e a t i n g r a t e

Light g a s e s a r e immediately vented through a g l a s s wool f i l t e r i n t o a 61 cm long i n f r a r e d c e l l i n a F o u r i e r Transform I n f r a r e d Spec t rometer . The c e l l was c a l - i b r a t e d f o r mixtures of HCN (200, 100, 50 and 25 ppm) d i l u t e d i n N 2 t o a t o t a l p r e s s u r e of 400 t o r r t o avoid t h e u n c e r t a i n t i e s of p r e s s u r e broadening by m i x t u r e s . A t t h e end of a d e v o l a t i l i z a t i o n run t h e c e l l and r e a c t o r chamber a r e f i l l e d w i t h n i t r o g e n t o g i v e a t o t a l p r e s s u r e of 400 t o r r and s i m u l a t e t h e c a l i b r a t i o n .

The c o n t r o l c i r c u i t i n t h i s i n v e s t i g a t i o n o p e r a t e d a Harr i son power supply Model 6269A i n t h e c u r r e n t program mode. I n t h i s mode h e a t i n g r a t e and f i n a l tempera ture a r e coupled over t h e e n t i r e f i n a l t empera ture range . The coupl ing between h e a t i n g r a t e and f i n a l temperature f o r t h e two s c r e e n m a t e r i a l s can be de- s c r i b e d by a s imple e q u a t i o n of t h e form l o g (?)=, T + B , where t h e parameter: f o r each s c r e e n a r e g iven i n Table I. The coupl ing between h e a t i n g r a t e and f i n a l tempera ture i s l o g a r i t h m i c i n a manner analogous t o Newton's law of h e a t i n g / c o o l i n g . For t h e s t a i n l e s s s t e e l s c r e e n t h e f i n a l t empera ture of 530 C i s a s s o c i a t e d w i t h a h e a t i n g r a t e of - 100 C/sec whi le a f i n a l t empera ture of 1000 C is a s s o c i a t e d w i t h a h e a t i n g r a t e of 600 C/sec. The maximum h e a t i n g r a t e ob ta ined f o r t h e t u n g s t e n s c r e e n was - 2000 C/sec f o r a f i n a l t empera ture of 1780 C .

Chemical S t r u c t u r e C h a r a c t e r i s t i c s of t h e Coals

The c o a l s examined i n t h i s i n v e s t i g a t i o n a r e t h e same as those p r e v i o u s l y r e p o r t e d i n an i n v e s t i g a t i o n of t a r y i e l d s and c h a r a c t e r i s t i c s ob ta ined from t h e d e v o l a t i l i z a t i o n of the c o a 1 . l i n Table 11. Figure 2 r e p r e s e n t s t h e l o c a t i o n of t h e c o a l s on t h e c o a l i f i c a t i o n band a s revea led by H / C and O / C v a l u e s . c o a l s r e l a t i v e t o t h e E a s t e r n bi tuminous c o a l s r e f l e c t s t h e d i f f e r e n c e s i n rank and , i n d i r e c t l y , g e o l o g i c sources . This f i g u r e a l s o r e v e a l s t h e maximum t a r y i e l d s obta ined from t h e s e c o a l s . These y i e l d s a r e impor tan t c h a r a c t e r i s t i c s of t h e d e v o l a t i l i z a t i o n behavior of a c o a l a s is t h e v a r i a t i o n i n tar y i e l d w i t h a p p a r e n t thermal dr ive . '

D e t a i l e d e l e m e n t a l a n a l y s e s f o r t h e c o a l s a r e g iven

The p o s i t i o n of t h e Western b i tuminous

F igure 3 i l l u s t r a t e s , t h e i n f r a r e d s t r u c t u r a l c h a r a c t e r i s t i c s of t h e c o a l s . V a r i a t i o n s i n i n f r a r e d s t r u c t u r a l c h a r a c t e r i s t i c s of a c o a l w i t h i t s e l e m e n t a l

1 9

composi t ion ( p o s i t i o n on t h e c o a l i f i c a t i o n band) have been p r e v i o u s l y d i s c ~ s s e ? . ' ~ ' ~ ' ~ The r e l a t i o n s h i p of t h e t a r y i c l d s and tempera ture s e n s i t i v i t y of t a r y i e l d s t o i n f r a r e d s t r u c t u r a l c h a r a c t e r i s t i c s of t h e p a r e n t c o a l h a s a l s o been p r e v i o u s l y d i s - c u s s e d . l Proceeding f r o m t h e low rank s i d e of t h e c o a l i f i c a t i o n band t o t h e h i g h rank s i d e t h e r e i s a n a p p a r e n t maximum i n a l i p h a t i c hydrogen a b s o r p t i o n ( - 3000 - 2750 c m - l ) around t h e l o c a t i o n of t h e Utah bi tuminous c o a l (H/C = 0.85, O / C = 0 . 1 3 ) . Such an apparent maximum i s i n d i r e c t l y observed i n t h e s p e c t r a of F i g . 3 , normalized w i t h r e s p e c t t o 1 mg of c o a l i n a K B r p e l l e t . I t i s more d i r e c t l y observnb1.e i n p l o t s of i n t e g r a t e d a b s o r b a x e v e r s u s sample s i z e f o r each of t h e c o a l s . The s l o p e s of such p l o t s g i v e a p p a r e n t e x t i n c t i o n of c o e f f i c i e n t s f o r each c o a l . The a l i p h a t i c e x t i n c t i o n c o e f f i c i e n t f o r t h e Utah c o a l i s about 24% g r e a t e r than t h a t of t h e P i t t s b u r g h seam bi tuminous c o a l . I t s t o t a l hydrogen c o n t e n t i s only about 3% g r e a t e r . The g r e a t e r apparent a l i p h a t i c hydrogen i n t h e Utah bi tuminous c o a l r e f l e c t s n o t only a d i f f e r e n c e i n t h e amount of hydrogen p r e s e n t a s a l i p h a t i c hydrogen, bu t a l s o t h e n a t u r e and d i s t r i b u t i o n of t h e molecular s p e c i e s t o which t h e a l i p h a t i c hydrogen f u n c t i o n a l groups a r e a t t a c h e d . 6

I n proceeding through t h e c o a l i f i c a t i o n band i t is a l s o noted t h a t t h e r e s o l u - t ion of t h e a romat ic hydrogen peaks ( - 3040 cm-', 680-920 cm-l) i n c r e a s e s w i t h rank. This i n c r e a s e i n r e s o l u t i o n is r e f l e c t e d i n t h e a p p a r e n t a romat ic hydrogen absorp- t i o n c o e f f i c i e n t s of t h e c o a l s . The i n t e g r a t e d a r e a a b s o r p t i o n c o e f f i c i e n t s f o r a r o m a t i c hydrogen g e n e r a l l y i n c r e a s e w i t h rank f o r t h e s e c o a l s . I f t h e s t r e n g t h of t h e bands a s s o c i a t e d w i t h a r o m a t i c hydrogen a b s o r p t i o n is an i n d i c a t i o n of t h e a r o m a t i c i t y of the c o a 1 , t h e n t h e s p e c t r a of t h e s e c o a l s i n d i c a t e a c o n s i s t e n t i n - c r e a s e i n a r o m a t i c i t y w i t h rank a s r e f l e c t e d by t h e p o s i t i o n on t h e c o a l i f i c a t i o n band diagram (Fig . 2 ) .

These s t r u c t u r a l c o n s i d e r a t i o n s a r e impor tan t because they l e a d t o g e n e r a l unders tanding of t h e r e l a t i o n s h i p between chemical s t r u c t u r a l c h a r a c t e r i s t i c s of a c o a l and i t s pr imary d e v o l a t i l i z a t i o n behavior . A p r e v i o u s r e p o r t demonstrated t h a t t h e i n f l u e n c e of chemica l s t r u c t u r e on d e v o l a t i l i z a t i o n f o r subbituminous and bi tuminous c o a l s i s most c l e a r l y r e f l e c t e d i n t h e pr imary (vacuum, d i s p e r s e phase , s m a l l p a r t i c l e s i z e ) t a r y i e l d s and tar C h a r a c t e r i s t i c s . ' t h a t t h e n i t r o g e n d i s t r i b u t i o n i n t h e pr imary v o l a t i l e s and char r e s i d u a l can a l s o be r e l a t e d t o s t r u c t u r a l c h a r a c t e r i s t i c s of t h e p a r e n t c o a l .

T h i s r e p o r t demonst ra tes

20

Nitrogen D i s t r i b u t i o n i n t h e D e v o l a t i l i z a t i o n Products Coal Ni t rogen i n t h e Char, T a r , L ight Gas S p e c i e s

Typica l mass f r a c t i o n d i s t r i b u t i o n s of t h e c o a l n i t r o g e n i n t h e d e v o l a t i l i z a - tiOn products a r e l i s t e d i n Table 111. T y p i c a l d i s t r i b u t i o n s are i l l u s t r a t e d i n F igs . 4-7. The d a t a i n d i c a t e s t h a t l i t t l e ( < 5%) of t h e c o a l n i t r o g e n is evolved a s HCN i n those runs c h a r a c t e r i z e d by f i n a l tempera tures of 700 C and below. In t h e 500 C t o 700 C f i n a l t empera ture r u n s , most of t h e v o l a t i l e n i t r o g e n i s i n the t a r s p e c i e s . A s t h e thermal d r i v e is i n c r e a s e d ( f i n a l tempera tures - 700 C t o - 950 C) HCN becomes a g r e a t e r component i n t h e v o l a t i l e s n i t r o g e n . The tempera ture dependence of t h e HCN e v o l u t i o n i n t h i s tempera ture range i s c o a l dependent . The subbituminous and Western bi tuminous c o a l s , f o r example, g i v e s h a r p e r i n c r e a s e s i n HCN e v o l u t i o n w i t h r e s p e c t t o f i n a l temperature t h a n t h e P i t t s b u r g h bi tuminous o r Alabama bi tuminous.

For a l l of t h e samples examined except t h e a n r t h r e c i t e , m o r e of t h e c o a l n i t r o - gen i s evolved a s an element of t h e t a r s p e c i e s t h a n a s HCN i n t h e < 1000 C r u n s . I n t h e range of c o n d i t i o n s , t h e r e t e n t i o n of c o a l n i t r o g e n i n t h e c h a r r e s i d u e i s similar f o r t h e subbi tuminous and Western b i tuminous c o a l s . The f r a c t i o n of c o a l n i t r o g e n r e t a i n e d i n t h e c h a r i s approximate ly t h e same f o r t h e same f i n a l temper- a t u r e . The tempera ture dependent n i t r o g e n r e t e n t i o n i n t h e c h a r s of t h e E a s t e r n b i t iminous c o a l s (h igh v o l a t i l e A P i t t s b u r g h seam, Alabama medium v o l a t i l e ) i s apprec iab ly d i f f e r e n t than those of t h e subbi tuminous and Western bi tuminous c o a l s . The c h a r s of t h e P i t t s b u r g h seam show l e s s n i t r o g e n v a r i a t i o n s w i t h f i n a l temper- t u r e . The medium v o l a t i l e bi tuminous c h a r s show n i t r o g e n v a r i a t i o n w i t h tempera ture s i m i l a r t o t h a t of t h e Western bi tuminous b u t a t h i g h e r l e v e l s of mass f r a c t i o n r e t e n t i o n .

Mass F r a c t i o n s of Coal Ni t rogen i n Tar

A l l of t h e c o a l s show subs tan t i -a l i n c r e a s e s i n n i t r o g e n evolved a s HCN f o r f i n a l t empera tures above 950 C . A p o r t i o n of t h i s i n c r c a s e is t h e r e s u l t of secondary c racking r e a c t i o n s of pr imary t a r vapors under t h e c o n d i t i o n s of i n c r e a s e d thermal d r i v e . As noted above, a p r e v i o u s study’ on t a r y i e l d s revea led t h a t t a r y i e l d s can be s u b s t a n t i a l l y modified by i n c r e a s i n g t h e h e a t i n g r a t e of t h e coa l . Reduct ion i n t h e t a r y i e l d s by an i n c r e a s e i n thermal d r i v e resu l t s i n a corresponding reduc- t i o n i n t h e c o a l n i t r o g e n evolved i n t h e t a r . Cracking of t h e n i t r o g e n - c o n t a i n i n g t a r s p e c i e s r e s u l t s i n t h e e v o l u t i o n of t h e n i t r o g e n a s HCN. The r e l a t i o n s h i p between t h e c o a l n i t r o g e n and the evolved tar s p e c i e s is i l . l u s t r a t e d i n F igs . 8-10..

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Figure 8 shows t h e f r a c t i o n s of Utah b i tuminous c o a l mass and c o a l n i t r o g e n evolved as tar and as a n element of t h e t a r s p e c i e s f o r v a r i o u s f i n a l t empera tures . Fig- u r e 9 shows p l o t s of t h e mass f r a c t i o n of c o a l evolved a t tar v e r s u s t h e mass f r a c - t i o n of coal n i t r o g e n evolved a s t a r , i r r e s p e c t i v e of thermal d r i v e c o n d i t i o n s . A s t h e t a r s p e c i e s a r e reduced by i n c r e a s i n g t h e t h e r m a l d r i v e , n i t r o g e n i s r e l e a s e d a s HCN from t h e t a r c racking p r o c e s s .

Mass F r a c t i o n s a s CHAR

F i g u r e s 10 and 11 p l o t t h e mass f r a c t i o n of t h e c o a l evolved a s char v e r s u s t h e mass f r a c t i o n of t h e c o a l n i t r o g e n evolved a s c h a r n i t r o g e n . A s w i t h t h e t a r p l o t s , upon e l e m i n a t i o n of t h e thermal h i s t o r y parameter , t h e r e i s an obvious s i m i l a r i t y i n t h e n i t r o g e n a v o l u t i n n of t h e subbi tuminous and bi tuminous c o a l s . The p l o t s i n d i c a t e that t h e main phase of t h e d e v o l a t i l i z a t i o n p r o c e s s is c h a r a c t e r - i z e d by n i t r o g e n r e t e n t i o n i n t h e char i n p r o p o r t i o n t o t h e f r a c t i o n of c o a l mass evolved a s c h a r . A t m a s s f r a c t i o n s of c h a r g r e a t e r than - 0 . 5 ( c h a r a c t e r i z e d by runs of 950 C f i n a l t empera ture and l e s s ) a l l of t h e c h a r s los t r e t a i n e d n i t r o g e n a t a rate much g r e a t e r t h a n a d d i t i o n a l mass l o s s .

Phenomenological D e s c r i p t i o n of Nitrogen Evolu t ion

A phenomenological d e s c r i p t i o n of t h e e v o l u t i o n of c o a l n i t r o g e n d u r i n g vacuum d e v o l a t i l i z a t i o n emerges from t h e i n v e s t i g a t i o n . For f i n a l t empera tures of 950 C and l e s s and a p p a r e n t h e a t i n g r a t e s of 600 C/sec and less, t h e tar and char. s p e c i e s g e n e r a l l y c o n t a i n 0 .7 o r more of t h e c o a l n i t r o g e n . In t h i s range of c o n d i t i o n s , tar removes c o a l n i t r o g e n i n p r o p o r t i o n t o t h e mass f r a c t i o n of c o a l evolved a s tar . Char retains n i t r o g e n i n p r o p o r t i o n t o t h e m a s s f r a c t i o n of c o a l evolved a s c h a r . The h a l a n c e of t h e c o a l n i t r o g e n e v o l v e s predominant ly a s HCN. Small b u t observable amounts of NH3 a r e produced a t low f i n a l tempera tures . t o be formed from low rank c o a l s .

More N H 3 a p p e a r s

The d i s t r i b u t i o n of t h e c o a l n i t r o g e n i n t h e t a r , c h a r o r l i g h t g a s e s produced d u r i n g d e v o l a t i l i z a t i o n is dependent on t h e rank of t h e p a r e n t c o a l i n a manner ana logous t o t h e d i s t r i b u t i o n of c o a l mass a s t a r , char o r l i g h t g a s e s . A n i n c r e a s e i n t h e f r a c t i o n of v o l a t i l e s evolved as t a r w i t h i n c r e a s e i n rank r e s u l t s i n a pro- p o r t i o n a t e i n c r e a s e i n n i t r o g e n e v o l u t i o n as an element of t h e tar s p e c i e s . A d e c r e a s e i n t a r y i e l d w i t h i n c r e a s e i n thermal d r i v e , results i n a p r o p o r t i o n a t e d e c r e a s e i n c o a l n i t r o g e n evolved a s t a r . gen is evolved as HCN. s t a b l e than lower r a n k c o a l s (See Reference 1 ) .

A s t h e t a r y i e l d d e c r e a s e s , t h e t a r n i t r o - Higher rank c o a l s appear t o produce t a r s more t h e r m a l l y

22

For f i n a l t empera tures g r e a t e r t h a n 950 C and h e a t i n g r a t e s i n e x c e s s o f 600 C/sec, Western bi tuminous and subbi tuminous c o a l s d i s p l a y t a r y i e l d r e d u c t i o n s a s g r e a t as 50-60% of t h e maximum ta r y i e l d . The c o a l n i t r o g e n evolved as tar i s p r o p o r t i o n a t e l y reduced. A t v o l a t i l e y i e l d s g r e a t e r than - 0.5 of t h e p a r e n t c o a l t he pr imary form of n i t r o g e n e v o l u t i o n from t h e c h a r is HCN. conversion l i t t l e i n c r e a s e i n t o t a l v o l a t i l e s by mass i s observed w h i l e s u b s t a n t i a l r e d u c t i o n s i n char n i t r o g e n l e v e l s a r e observed.

A t t h e s e l e v e l s of

Rela t ionship of Nitrogen D e v o l a t i l i z a t i o n Behavior t o Coal S t r u c t u r a l C h a r a c t e r i s t i c s , S t r u c t u r a l Models

The chemical n a t u r e of t h e n i t r o g e n d i s t r i b u t i o n i n t h e mix of molecular s p e c i e s p r e s e n t i n t h e parent c o a l i s i n d i c a t e d by t h e fo l lowing phenomenlogical observa- t i o n s : (1) n o n - p r e f e r e n t i a l e v o l u t i o n of c o a l n i t r o g e n as c h a r , t a r o r l i g h t g a s dur ing t h e d e v o l a t i l i z a t i o n p r o c e s s ; ( 2 ) t h e n i t r o g e n d i s t r i b u t i o n i n t h e devola- t i l i z a t i o n products ( t a r , c h a r , l i g h t gas ) v a r i e s w i t h rank and thermal d r i v e a s does t h e d i s t r i b u t i o n of c o a l mass a s c h a r , tar and l i g h t g a s ; ( 3 ) HCN i s t h e dominant n i t rogen-conta in ing l i g h t g a s ' o b s e r v e d i n rap id-hea t ing ; d i s p e r s e phase devo1.a t i l i za t ion .

In t h e c o n t e s t of r e l a t e d i n v e s t i g a t i o n s and a p r e v i o u s r e p o r t on tar y i e l d s / c h a r a c t e r i s t i c s , t h e o b s e r v a t i o n s i n d i c a t e : (1) n i t r o g e n i s uni formly d i s t r i b u t e d throughout t h e mix of molecular s p e c i e s p r e s e n t i n t h e p a r e n t c o a l , i r r e s p e c t i v e of rank; (2 ) t h e pr imary type of ni t rogen-bonding p r e s e n t i n t h e p a r e n t c o a l i s a s a heteroatom i n an a romat ic r i n g system, i . e . , pyr id ine- type ; (3) v a r i a t i o n s w i t h rank i n t h e n i t r o g e n d i s t r i b u t i o n s i n t h e d e v o l a t i l i z a t i o n p r o d u c t s can be under- s tood on t h e b a s i s of a s h i f t w i t h rank i n a condensa t ion f requency f u n c t i o n ( t h e d i s t r i b u t i o n of molecular s p e c i e s a s c h a r a c t e r i z e d by t h e number of fused r i n g s / s t r u c t u r e ) .

T h i s d e v o l a t i l i z a t i o n s t u d y as w e l l as o t h e r s i n d i ~ a t e ~ . ~ t h a t HCN i s t h e p r i n c i p a l n i t rogen-conta in ing l i g h t g a s evolved d u r i n g d i s p e r s e phase , rap id-hea t ing c o a l d e v o l a t i l i z a t i o n . S t u d i e s performed by Houser ,g , e t . a l . and Axworthy," e t . a l . i n d i c a t e HCN i s t h e p r i n c i p a l l i g h t g a s evolved from t h e thermal decomposi- t i o n of pyr id ine- type n i t r o g e n compounds. I n a d d i t i o n , r e c e n t s t u d i e s performed by Deno, e t . al.11 i n d i c a t e t h a t t h e n i t r o g e n p r e s e n t i n t h e p a r e n t c o a l is found as an heteroatom i n a romat ic r i n g s t r u c t u r e s . Taking i n t o account t h e known h i g h l y a romat ic n a t u r e of c o a l s , t h e d a t a of t h i s s tudy i n d i c a t e t h a t t h e pr imary form of n i t r o g e n appears t o be as a he teroa tom i n a r o m a t i c r i n g s t r u c t u r e s .

I

2 3

A s noted i n a n earl ier r e p o r t ,' d i s t i n g u i s h i n g f e a t u r e s of t h e d e v o l a t i l i z a - t i o n behavior of a c o a l a r e i t s maximum t a r y i e l d and t h e s e n s i t i v i t y of t a r y i e l d t o the c o n d i t i o n s of t he rma l d r i v c . I t was shown, f o r example, t h a t t h e P i t t s b u r g h seam bi tuminous c o a l gave a maximum t a r y i e l d ~ 40% g r e a t e r than t h e Utah bituminous c o a l , I 50% g r e a t e r t h a n e i t h e r the Colorado bi tuminous or Alabama bituminous c o a l s , - 85% g r e a t e r t h a n t h e two subbi tuminous c o a l s . Only a s m a l l f r a c t i o n of t h e l i g n i t e was evolved a s tar and t h e a n t h r a c i t e gave only l i g h t g a s e s . The P i t t s b u r g h seam c o a l (HVA) and Alabama bi tuminous c o a l (MVB) gave t a r y i e l d s which were r e l a - t i v e l y i n s e n s i t i v e t o changes i n thermal d r i v e by comparison t o t h e Western bi tuminous and subbi tuminous c o a l s . T o t a l vacuum v o l a t i l e y i e l d s do not va ry s i g - n i f i c a n t l y w i t h r ank u n t i l c o a l s w i th c h a r a c t e r i s t i c s of the medium v o l a t i l e bi tuminous c o a l . Tinis r e p o r t i n d i c a t e s t h a t t h e n i t r o g e n d i s t r i b u t i o n i n t h e de- v o l a t l l i z a t i o n p r o d u c t s r e f l e c t s t h e s e p a t t e r n s .

Thus moving a l o n g the c o a l i f i c a t i o n band from t h e low rank t o the h igh rank s i d e , t h e t a r y i e l d becomes a g r e a t e r f r a c t i o n of t h e t o t a l v o l a t i l e s evolved and t h e primary tars formed appea r t o be more t h e r m a l l y . s t a b l e . Correspondingly, more of the parent c o a l n i t r o g e n i s evolved as t a r and i s r e t a i n e d by t h e thermal ly s t a b l e t a r s of these c o a l s .

The d e v o l a t i l i z a t i o n d a t a , i n d i c a t e t h a t an i n c r e a s e i n a condensat ion index ( s h i f t t o a h i g h e r ave rage number of t h e frequency f u n c t i o n d e s c r i b i n g #fused r i n g s / molecular s p e c i e s ) and a r o m a t i c i t y of c o a l w i th p o s i t i o n on t h e c o a l i f i c a t i o n band p rov ides a r e a s o n a b l e e x p l a n a t i o n of changes i n behavior w i th rank. The chemical n a t u r e of t h e n i t r o g e n d i s t r i b u t i o n i n t h e parent c o a l f o r c e s t h e c o a l n i t r o g e n d e v o l a t i l i z a t i o n behav io r t o r e f l e c t the c o a l mass d e v o l a t i l i z a t i o n behavior .

The v a r i a t i o n i n d e v o l a t i l i z a t i o n behav io r w i t h rank appea r s t o suppor t some e a r l i e r a t t e m p t s t o deve lop a model of c o a l c o n s t i t u t i o n based on t h e average number of fused r i n g s i n a molecular u n i t ( l a m e l l a ) of t h e c o a l . A model such as sugges t ed by Ayre and Essenh igh lz and l a t t e r modif ied by Scaroni and Essenhigh13 a p p e a r s ab le t o p r o v i d e a r easonab le e x p l a n a t i o n of behavior with some q u a l i f i c a t i o n s The d a t a of t h i s s tudy i n d i c a t e a change i n d e v o l a t i l i z a t i o n behavior w i th r e s p e c t t o t o t a l y i e l d a t a carbon c o n t e n t lower than 90%. The d a t a a l s o i n d i c a t e s a change i n d e v o l a t i l i z a t i o n behavior w i th r e s p e c t t o the y i e l d s and c h a r a c t e r i s t i c s much lower than 90%. I t is b e l i e v e d t h a t a s t a t i s t i c a l f u n c t i o n of t h e type d e s c r i b e d above showing a pronounced s h i f t i n c h a r a c t e r i s t i c s i n t h e 82-85% carbon l e v e l would more adequa te ly r e f l e c t behavior observed i n t h e s e s t u d i e s .

24

The d e v o l a t i l i z a t i o n d a t a of t h i s s tudy and t h e p r e v i o u s t a r s t u d y i n d i c a t e t h a t c o a l does behave a s i f i t d e v o l a t i l i z e s i n two s t a g e s . The main s t a g e (mass f r a c t i o n convers ions of - .4-.5) of v o l a t i l e e v o l u t i o n r e q u i r e s r e l a t i v e l y low f i n a l tempera tures and i s fo l lowed by a second s t a g e of v o l a t i l e e v o l u t i o n r e q u i r i n g tempera tures i n e x c e s s of 1000 C f o r a p p r e c i a b l e r a t e s . The c o a l n i t r o g e n does evolve as i f i t were conta ined i n two components. The two-component h y p o t h e s i s of c o a l c o n s t i t u t i o n was f i r s t no ted by Clark and Wheeler14 and l a t e r emphasized by Essenhigh and Howard15 t o e x p l a i n d e v o l a t i l i z a t i o n behavior .

However, r a t h e r than i d e n t i f y i n g t h e e a s i l y evolved v o l a t i l e matter as being genera ted by t h e weakly bonded amorphous m a t e r i a l a s s o c i a t e d wi th s t a c k e d r i n g s t r u c t u r e s , t h e d a t a sugges t t h e e a s i l y evolved n i t r o g e n t o be a s s o c i a t e d w i t h r i n g s t r u c t u r e s s u s c e p t i b l e t o thermal c racking and/or v o l a t i l i z a t i o n a t t empera tures o f 950 C o r below. V a r i a t i o n s w i t h rank i n e a s i l y evolved n i t r o g e n e x p e l l e d a s t a r o r HCN r e f l e c t v a r i a t i o n s i n t h e r i n g s i z e d i s t r i b u t i o n f u n c t i o n w i t h rank c h a r a c t e r - i s t i c s . The P i t t s b u r g h seam bi tuminous c o a l e v o l v e s more c o a l n i t r o g e n a s t a r t h a n t h e Utah bi tuminous c o a l because i t s parent n i t r o g e n i s conta ined i n r i n g s t r u c - t u r e s more thermal ly s t a b l e , t h a t i s , of g r e a t e r degree of r i n g condensa t ion and having fewer a s s o c i a t e d f u n c t i o n a l groups. For t h e same r e a s o n , t h e Alabama bi tuminous (medium v o l a t i l e ) c o a l i n i t i a l l y e x p e l s most of i t s n i t r o g e n a s t a r . The Alabama bi tuminous y i e l d s less t o t a l v o l a t i l e s than t h e h igh v o l a t i l e b i tuminous c o a l s because a g r e a t e r f r a c t i o n of i t s n i t r o g e n i s a s s o c i a t e d w i t h n o n - v o l a t i l e r i n g s t r u c t u r e s . That i s i t c o n t a i n s a l a r g e f r a c t i o n of s t r u c t u r e s t o o l a r g e t o be v o l a t i l i z e d b e f o r e char - incorpora t ing secondary r e a c t i o n s "polymerize" t h e s p e c i e s i n t h e c h a r m a t r i x .

This s t u d y on n i t r o g e n e v o l u t i o n and t h e p r e v i o u s s tudy d e a l i n g w i t h t a r y i e l d s and c h a r a c t e r i s t i c s ob ta ined from a v a r i e t y of c o a l s i n d i c a t e s :

1. I n vacuum d e v o l a t i l i z a t i o n c o n d i t i o n s , c o a l behaves a s i f i t c o n t a i n s two v o l a t i l e components, a s p r e v i o u s l y noted .

2 . L i g n i t e t o h i g h v o l a t i l e bi tuminous c o a l s can be d i f f e r e n t i a t e d w i t h r e s p e c t t o d e v o l a t i l i z a t i o n y i e l d s , p r i m a r i l y t a r y i e l d and c h a r a c t e r i s t i c s .

3 . Coal n i t r o g e n d i s t r i b u t i o n i n t h e v o l a t i l e products f o r subbi tuminous c o a l s and h i g h e r r a n k s r e f l e c t s t h e c o a l mass d i s t r i b u t i o n i n t h e v o l a t i l e p r o d u c t s .

25

4 . Coal n i t r o g e n f o r subbituminous and h igher rank c o a l s behaves a s i f i t were inco rpora t ed a s a n he t e roa tom i n t h e a romat i c r i n g system of t h e parent c o a l .

5. A s p rev ious ly n o t e d , v a r i a t i o n s i n d e v o l a t i l i z a t i o n behavior w i th rank appear t o r e f l e c t a v a r i a t i o n i n t h e degree of r i n g condensat ion present i n the c o a l m a t r i x .

6 . V a r i a t i o n s i n d e v o l a t i l i z a t i o n behav io r (more s p e c i f i c a l l y , t a r and n i t r o - gen e v o l u t i o n ) w i t h r ank r e E l e c t a s h i f t i n t h e c h a r a c t e r i s t i c s of a r ing- s i z e d i s t r i b u t i o n f u n c t i o n wi th rank.

TABLE I

COUPLING BETWEEN FINAL TEMPERATURE AND HEATING RATE

Screen M a t e r i a l - 19 - b T Range, O C

S t a i n l e s s s teel 1 . 9 6 10-3 0.92 530 - 950

Tungsten 6.50 x 2 . 1 6 1000 - 1750

26

REFERENCES

1.

2.

3.

4 .

5.

6.

7 .

8.

9.

10.

, I 11.

I 12 .

I 13.

1 4 . 1 15.

F r e i h a u t , J . D. and Seery, D. J . , h e r . Chem. SOC. Div. of F u e l Chem. P r e p r i n t s , - 2 6 , No. 2 , 133 (1981) .

Brown, J . K . and Hirsch , P. B . , Nature , 175, 229 (1955).

F u j i i , S . , O s a w a , Y , and Sugimura, H . , F u e l , 2, 68 (1970) .

Solomon, P. R . , h e r . Chem. SOC. Div. of Fuel Chem. P r e p r i n t s , 2, No. 3, 184 (1979) and Advances i n Chemistry ( t o be p u b l i s h e d ) .

P a i n t e r , P. C . , e t . a l . Applied Spectroscopy ( t o be p u b l i s h e d ) .

Bellamy, L . J. The I n f r a r e d S p e c t r a of Complex Molecules , John Wiley & Sons, New York (1975).

Pohl , J . H. and Sarofim, A. F . , S i x t e e n t h Symp ( I n t e r n ) on Combustion, The Combustion I n s t i t u t e , P i t t s b u r g h , 491 (1979) .

B l a i r , D. W . , Wendt, J . D . L , and Bar tok , N . , S ix teench Symp (Tncern) on Combus- t i o n , The Combustion I n s t i t u t e , P i t t s b u r g h , 475 (1977).

Houser, T. J . , e t . a l . , I n t . Jr . of Chem. K i n e t i c s , X T T , 555 (1980)

Axworthy, A.E . , e t . a l . , F u e l , 57 , 29 (1978) .

Deno, N . C . , Pennsylvania S t a t e U., Dept. of Chem, P r i v a t e Communication.

Ayre, J. L. and Essenhigh, R . H . S h e f f i e l d Univ. Fue l SOC. J r . , 8, 44 (1957) .

Scaroni , A. W . and Essenhigh, R. H . , A m e r . Chem. SOC. Div. of Fue l Chem.. Pre- p r i n t s , 3, No. 4 , 124 (1978).

Clark , A. H . and Wheeler, R. V . , Trans . Chem. SOC., 103, 1754 (1913) .

Essenhigh, R. H . and Howard, J . B . , The Pennsylvania S t a t e U . , S t u d i e s , 2 (1971) .

27

H H

w cl m 2

i P v

cn Y

3s d d d d d d d

h

a 2 & 2 2 u N

. 4 . ? 9 ? ? ? ? * u u - ? m d o m r . a u w

m o o o o o o o

h m r . m C n m N .- a Z m r o d r - m u ~

a u w m o o o o o o o

* u u - ? m d o m r . . 4 . ? 9 ? ? ? ?

n m 5 5

U U 3

m

P-

3 W

0

m

0 0 4 co 0

co 3 W P-

O

VI

0 ?

m m m 0

0

N m m

0 ?

\o m m

0 ?

m 4 4 rl

0

0

N U d

B

m \o 3

? 0

. . . 0 0 0

ro P - P - m o u m ? c o d . . 0 0 0

; i o o P - w V I U L h o N m o o L n u c a - 4 0 c o a l

V , O G O O O O O . .

28

TABLE I11 - 1

NITROGEN DISTRIBUTIONS IN DEVOLATILIZATION PRODUCTS

Subbituminous 2 (SUB B)

Tf (OC)

520

600

745

820

890

945

950

1040

1090

1160

1240

1365

1390

1600

1700

1780

fNCHAR

0.99

0.76

0.67

0.63

0.57

0.57

0.53

0.48

0.40

0.31

0.28

0.17

0.08

0.10

0.08

---

fNtar

0.05

0.24

0.19

0.28

0.22

0.12

0.11

0.17

0.14

0.07

0.06

0.06

0.04

0.04

0.04

0.03

fNHCN

---

0.01

0.10

0.17

0.21

0.20

0.30

0.30

0.40

0 .63

0.65

0.66

0.61

0.54

0.92

0.87

EfN -

1.04

1 . 0 1

0.96

1 .00

1.00

0.89

0.94

0.95

0.94

1 .01

0.99

0.89

0 .73

0 .68

1 .03

0.90

29

TABLE 111 - 2

NITROGEN D I S T R I B U T I O N S I N DEVOLATILIZATION PRODUCTS

Utah Bituminous

fNCHAR

530

595

745

790

880

915

935

1020

1090

1160

1240

1390

1600

1700

1730

0.81

0.66

0.58

0.57

0.49

0.48

0.51

0.42

0.40

0.44

0.30

0.20

0.20

0.13

0.10

f N t a r

0.04

0.22

0.26

0.27

0.25

0.24

0.30

0.29

0.24

0 . 2 2

0 . 2 1

---

0.10

0.06

0.05

(HVB)

f N ~ ~ ~

0 . 0 1

0 . 0 1

0.08

0.09

0.17

0.17

0.13

O . ; G

0.25

0.38

0.51

0.61

0.67

0.72

0.96

0.86

0.89

0.92

0 .93

0 .91

0.89

0.94

0.87

0.89

1.04

1 . 0 2

0 .81

0.97

0.91

1.11

30

TABLE I11 - 3

NITROGEN DISTRIBUTIONS IN DEVOLATILIZATION PRODUCTS

Pittsburgh Bituminous (HVA)

IfN __ fNRCN _ _ ~

0 . 0 1 1.11

0 . 0 1 1.00

0.00 1 .03

0.05 1 . 0 1

0.05 1 .05

Tf(OC)

565

5 85

618

735

0 . 6 1

0 . 6 1

0 .58

0.55

0.49

0.38

0.45

0 .41

745 0.59 0 .41

775 0.52 0.41 0.06 0.99

830 0 . 5 3 0.39 0.09 1.01

855 0.54 0.43 0.10 1.07

915

935

1040

0.46 0.36 0.10 0.96

0 .55

0.44

0.36 0 .08 1 .09

0.40 0.10 0.94

1090

1107

1125

0 .50

0 .41

0 .39

0.60

0.40

0.39

0.43

0.28

0.12 1 . 2 1

0.24 1.04

0.17 0.95

0.22 1.11

0.20 0.80

1165 0.46

0.32 1220

1220 0.39 0.36 0.33 1.08

1300 0.29 0.54 0 .30 1.13

1450 0 . 3 3 0.19 0.33 0.85

1450 0.26 0.30 0.37 0.93

1700 0.04 --- 0.43 0.47

1780 0.06 0.15 0 .28 0.49

31

Fig. 1 Heated Gr id Apparatus

Fig. 3 I R S p e c t r a of Coals

1.00,

0- 0 0.1 0.2 0.3

OIC, atomic ratio

Fig . 2 Coal Band Locat ion

0 W A R N

0 1 A R N

D HCN

WYOMING SUBBITUMINOUS B

v)

FINAL TEMPERATURE. "C

Fig . 4 Nit rogen D i s t r i b u t i o n : Subbituminous Coal

32

COLORADO BITUMINOUS

60

A A * * * 8 8 600 IOUU 1400 18ou

Utah bituminous coal

A HCN Tar nitrogen

0 Char nitrogen 1.0

0

FINAL TEMPERATURE. “C

- 40 A 8 Tar

e Tar N

30 -

PITTSBURGH BITUMINOUS (PBI

:. a

0.8 = A Percent :I . * . *

A ‘ 8 8 initial 20 - ’ mass

e IN, 0.0 - 0 0

mass Iractlon a

8 . 10 - 4 8 of coal 08

nitrogen 0.4 - 00: m 0 . .. 0

0

FINAL. TEMPERATURE. “C

0 . 2 - 5 * * * 0 . . @ 0 500 700 900 1100 1300 1500 1700 Final temp., ‘C ab A

A h . O C

OJ--4 ’ I I I I

Fig. 5 Nitrogen Distribution: Fig. 7 Nitrogen Distribution in Colorado Bituminous Coal Pittsburgh Bituminous Coal

Devolatilization Products

1,. linal temperature. ‘C Fig. 6 Elass Fraction of Coal Mass and Coal Nitrogen vs. Final Temperature for Utah Bituminous Coal Fig. 6 Nitrogen Distribution:

Utah Bituminous Coal

33

ftaP mass lractlon

01 coal evolved as tar

0.4

0.3

0.2

0.1

0 0 0.1 0.2 0.3 0.4

IN, mass lractlon 01 coal nitrogen evolved as tar

Fig. 9 Mass F r a c t i o n of Coal a s Tar vs. F r a c t i o n of Coal Ni t rogen a s Tar

Subbituminous 2

NO char

Fig . 10 Mass F r a c t i o n of Coal a s Char v s . F r a c t i o n of m a l Ni t rogen a s Char

Utah bituminous

- s 5 0.6

0.4

-

0.2

0 0 0.2 0.4 0.6 0.8 1.0

NO char

Fig . 11 Mass F r a c t i o n of Coal as Char vs. F r a c t i o n of Coal Ni t rogen a s Char

34

MINERAL MATTER EFFECTS ON THE RAPID PYROLYSIS AND HYDROPYROLYSIS OF A BITUMINOUS COAL

Howard D. F rank l in , W i l l i a m A. P e t e r s , Jack B. Howard

Department of Chemical Engineering and Energy Laboratory, Massachusetts I n s t i t u t e of Technology, Cambridge, Mass. 02139

Previous r e sea rch a t M.I .T . on r a p i d c o a l p y r o l y s i s has d e a l t w i t h t h e k i n e t i c s of evo lu t ion of i n d i v i d u a l products a s a func t ion of tempera ture , pressu re , p a r t i c l e s i z e , r e a c t i v e gas, and c o a l type (1-5). S tud ie s e l sewhere have shown t h a t c o n s t i t u e n t s of c o a l mine ra l matter a f f e c t s i g n i f i c a n t l y o t h e r types of c o a l conversion r e a c t i o n s (6-14). S p e c i f i c a l l y , c l a y s found i n c o a l have been shown t o a f f e c t c o a l ca rbon iza t ion (61, and t o c a t a l y z e H2 t r a n s f e r t o c o a l and c o a l model compounds ( 7 , 8 ) . P y r i t e , an impor tan t mine ra l i n East- e rn U.S. coa ls , is a s t rong c a t a l y s t f o r c o a l hydro l ique fac t ion (7-11), wh i l e c a l c i t e promotes steam and CO g a s i f i c a t i o n of c o a l (12 ,13) . Even q u a r t z , though chemically i n e r t , a f f e c t s hydro l ique fac t ion by a c t i n g a s a d i l u e n t t o agglomeration (14). Despi te this importance of minera l conten t i n c o a l thermo- chemistry, l i t t l e work has been done on a d d i t i v e e f f e c t s on r a p i d c o a l pyrolysis. Therefore t h i s study was conducted t o determine s y s t e m a t i c a l l y how t h e important minera ls p re sen t i n c o a l i n f l u e n c e t h e y i e l d s of i n d i v i d u a l devola- t i l i z a t i o n products.

2

EXPERIMENTAL

The c o a l used, descr ibed i n Table 1, w a s a P i t t sbu rgh No. 8 Seam bituminous coa l from t h e I r e l a n d Mine of t h e Consol ida t ion Coal Company. Mine ra log ica l a n a l y s i s w a s by Four ie r Transform I n f r a r e d Analys is (FTIR) of t h e low tempera- t u r e ash of t he c o a l (15). P y r i t e conten t w a s n o t measured d i r e c t l y , bu t t h e pyr i te -by-d i f fe rence va lue ag rees w e l l w i th measured p y r i t i c s u l f u r va lues f o r o t h e r s a m p l e s from t h e same mine (16). (45-53pm) and a f r a c t i o n of t h i s r a w sample was r e t a ined t o o b t a i n p y r o l y s i s d a t a on whole coa l . The remainder of t h e sample was e x t r a c t e d w i t h concen- t r a t e d HF and H C 1 t o remove i t s n a t i v e c l a y s , c a l c i t e , and q u a r t z , and w a s then subjec ted t o f loa t - s ink sepa ra t ion i n a 2.50 s p e c i f i c g r a v i t y f l u i d t o remove p y r i t e . The r e s u l t i n g demineralized c o a l conta ined 4.3% by weight minera l matter, most of it p y r i t e .

The c o a l w a s ground t o -270+325 US mesh

Mineral a d d i t i v e s r ep resen t ing each of t h e major mine ra l c o n s t i t u e n t s of t h i s c o a l were s tud ied . These a r e l i s t e d i n Table 2. Acid-treated montmoril- l o n i t e , prepared by e x t r a c t i n g w i t h H C 1 a p o r t i o n of t h e montmor i l lon i te sample, w a s used t o s tudy t h e e f f e c t of s o l i d a c i d i t y on p o s s i b l e c l a y c a t a l y s i s of py ro lys i s . Shale was obta ined from t h e P i t t s b u r g h No. 8 Seam, and is repre- s e n t a t i v e of t h e n a t i v e c l ays found i n t h i s coa l . All minera l a d d i t i v e s were ground t o 2-40 u m g r a i n s i z e , and added t o t h e c o a l by co-s lur ry ing wi th water i n concent ra ted suspension f o r 24 hours.

A t high temperatures and under t h e reducing cond i t ions of c o a l py ro lys i s ,

In orde r t o determine whether t h e e x t e n t of con a c t w i t h the c o a l c a l c i t e and p y r i t e w i l l decompose t o C a O and p y r r h o t i t e (FeSg+x, O<x<O.3) respec t ive ly . a f f e c t s t h e c a t a l y t i c p r o p e r t i e s of t h e s e p a r t i c u l a r minera ls , a d d i t i o n a l sources of CaO and p y r r h o t i t e were t r i e d as w e l l . FeS04, which is completely water

35

s o l u b l e , w a s added t o t h e c o a l by impregnation from s o l u t i o n . Under py ro lys i s condi t ions i t should decompose t o p y r r h o t i t e . C a O was added i n a manner s i m i - l a r t o t h a t f o r t h e mine ra l a d d i t i v e s .

The p y r o l y s i s appa ra tus and procedures have been descr ibed p rev ious ly (2,17,18). f o l d s of a 325 US mesh s t a i n l e s s steel sc reen and he ld between two e l ec t rodes i n e i t h e r a l eng th of g l a s s p i p e o r a s t a i n l e s s s teel p re s su re v e s s e l . c o a l i s heated by e l e c t r i c a l l y hea t ing t h e screen . The v e s s e l and i t s gaseous conten ts remain c l o s e t o room temperature throughout t h e run and thus t h e v o l a t i l e s are quenched almost i n s t an taneous ly on escape from t h e coa l p a r t i c l e s . useof achromel-alumel thermocouple (75 pm bead d iameter ) pos i t i oned wi th in t h e f o l d s of t h e s c r e e n a longs ide t h e c o a l p a r t i c l e s . Heat t r a n s f e r c a l c u l a t i o n s show t h a t a t p r e s s u r e s of 1 a t m and hea t ing rates of 1000 K / s o r less, c o a l particles and thermocouple beads 80 pm o r l ess i n diameter c l o s e l y follow the temperature of t h e s c r e e n and a r e s p a t i a l l y i so the rma l .

B r i e f l y , a t h i n h o r i z o n t a l l a y e r of c o a l i s sandwiched between t h e

The

The e n t i r e t ime-temperature h i s t o r y of t h e sample is recorded by

A l l t h e r e a c t i o n products were c o l l e c t e d . Gases and low b o i l i n g l i q u i d s were trapped on l i p o p h i l i c so rben t s and subsequent ly analyzed by gas chromatography. Char w a s determined g rav ime t r i ca l ly , and w a s f u r t h e r cha rac t e r i zed by elemental a n a l y s i s . Tar (room temperature condensibles) was co l l ec t ed on a f i l t e r a t t h e r e a c t o r o u t l e t and by a methylene ch lo r ide wash of t h e r e a c t o r i n t e r n a l s , and i t s y i k l d w a s determined g rav ime t r i ca l ly . T o t a l material bal- ances usua l ly exceeded 95%.

All runs were preformed a t hea t ing r a t e s of about 1000 K / s w i t h holding t imes of 0 o r 5 s a t t h e maximum temperature a t t a i n e d , and cool ing rates of about 200 K / s . These elements of t h e t ime-temperature h i s t o r y p e r t a i n only t o t h e parent sample s i n c e t h e v o l a t i l e s , once formed, r ap id ly escape t h e s a m p l e and are quenched as mentioned above. Demineralized, ca l c i t e -p re t r ea t ed , and CaO-pretreated samples were hea ted i n 1 a t m H e t o temperatures i n the range 800 t o 1400 K f o r both 0 and 5 s hold ing t i m e s . Other samples were pyrolyzed i n helium a t tempera tures nea r 1300 K f o r 5 s hold ing times, and a t temperatures nea r 1000 K f o r 0 s hold ing times. I n hydropyrolys is runs , samples were hea ted i n 69 atm H2 t o tempera tures between 800 and 1400 K f o r t h e demineralized c o a l , and t o one temperature, gene ra l ly near 1100 K, f o r t h e p r e t r e a t e d samples. Only 0 s hold ing t i m e s were used i n hydropyrolys is runs.

RESULTS

Pyro lys i s i n H e l i u m

The t o t a l y i e l d of v o l a t i l e s and t h e y i e l d of tar obta ined from pyro lys i s of t h e demineralized c o a l t o d i f f e r e n t temperatures i n 5 s holding time runs are shown i n F ig . 1. Each d a t a po in t r e p r e s e n t s t h e cumulative y i e l d from one exper imenta l run and i s a s s o c i a t e d wi th a s p e c i f i c time-temperature h i s - t o ry . The curves r e p r e s e n t s imple f i r s t - o r d e r r e a c t i o n models f i t t e d t o the da ta , and are used t o i n d i c a t e t r ends i n the d a t a . The e r r o r b a r s r ep resen t - +1 s tandard d e v i a t i o n from t h e y i e l d c a l c u l a t e d by t h e f i t t e d model. Heating and cool ing rates d i d n o t exac t ly reproduce from run t o run , and thus the hold ing o r peak tempera ture obta ined i s n o t n e c e s s a r i l y a good r ep resen ta t ion of t h e e n t i r e t ime-temperature h i s t o r y of a run. Therefore the f i t t e d models

36

were used t o genera te equ iva len t peak o r holding temperatures f o r each run. The model parameters were used t o determine a c a l c u l a t e d y i e l d of a given product f o r each a c t u a l time-temperature h i s t o r y . These y i e l d s were then compared w i t h y i e l d s c a l c u l a t e d us ing t h e s a m e parameters and i d e a l i z e d ( l i n - ear 1000 K/s heatup, 0 o r 5 s hold t ime, l i n e a r 200 K/s cooldown) time-temper- a t u r e h i s t o r i e s . The peak o r holding tempera ture of t h e i d e a l i z e d h i s t o r y having t h e same ca lcu la t ed y i e l d as t h a t of t h e a c t u a l h i s t o r y was picked as t h e temperature r e p r e s e n t a t i v e of t h e run. As a r u l e equ iva len t tempera tures f o r d i f f e r e n t products were wi th in 30 K of t h e corresponding observed peak o r holding temperature.

Resu l t s f o r r a w c o a l and f o r clay-,quartz-, and i ron -p re t r ea t ed s a m p l e s a r e shown i n Figs. 2-5. i n d i c a t e demineralized c o a l y i e l d s , wh i l e each letter r e p r e s e n t s one run wi th a sample p r e t r e a t e d wi th a p a r t i c u l a r minera l o r compound as s p e c i f i e d i n Table 2. P o i n t s l a b e l l e d "W" r ep resen t runs wi th r a w (undemineralized) coa l .

The curves and e r r o r b a r s p l o t t e d on a l l t h e s e graphs

There a r e i n gene ra l few e f f e c t s on pyro lys i s due t o any of t h e s e minera ls . F igures 2 and 3 show t h a t t h e t o t a l y i e l d of v o l a t i l e s and t h e y i e l d of tar are unaf fec ted by these a d d i t i v e s . While t h e r e are no p o i n t s i n F ig . 3 f o r p y r i t e o r F e S 0 4 , o the r runs no t p l o t t e d showed these a d d i t i v e s t o have no e f f e c t on tar y i e l d s . ane y i e l d s (Fig. 4 ) a r e , however, s i g n i f i c a n t l y reduced by p y r i t e and FeS04 ("P" and "F" po in t s ) . K a o l i n i t e suppresses t h e y i e l d of l i g h t l i q u i d hydrocarbons (Fig. 5 , "K" p o i n t s ) , which c o n s i s t mostly of BTX range compounds.

Data f o r most o t h e r products show similar t r e n d s . Meth-

Resu l t s f o r calcium minera ls have been r epor t ed previous ly ( 1 9 ) . To summarize them, both C a O and CaCO i n c r e a s e char y i e l d s , whi le s t r o n g l y de- c reas ing tar y i e l d s and s l i g h t l y reducing y i e l d s of o t h e r hydrocarbon vola- t i l es . Evolu t ion of CO i s enhanced by these a d d i t i v e s by a n amount approxi-

3 mately p ropor t iona l t o calcium loading. Comparison of C02 y i e l d s from CaCO p r e t r e a t e d c o a l w i th those from demineralized c o a l and pure c a l c i t e i n d i c a t e s t h a t c a l c i t e i n t h e presence of c o a l decomposes y i e l d i n g C 0 2 a t lower temper- a t u r e s than i t does when pyrolyzed a lone .

Py ro lys i s i n Hydrogen

3

E f f e c t s of minera ls i n hydropyrolys is were determined i n a similar manner t o Simple f i r s t - o r d e r models w e r e f i t t e d t o hydropyrolys is t h a t used f o r py ro lys i s .

d a t a from demineralized coa l , and t h e r e s u l t i n g curves w i t h e r r o r b a r s se rved a s a b a s i s of comparison f o r t h e da t a from hydropyrolys is of minera l - t rea ted coa l s .

Few of t h e minera ls were found t o in f luence hydropyrolys is behavior t o any s i g n i f i c a n t ex ten t . To ta l y i e l d of v o l a t i l e s (Fig. 6 ) is no t a f f e c t e d by any of t h e a d d i t i v e s t r i e d , although tar y i e l d s a r e reduced s l i g h t l y by a d d i t i o n of s h a l e o r c a l c i t e , and reduced s t rong ly by a d d i t i o n of CaO, kao- l i n i t e , o r ac id- t rea ted montmor i l lon i te ( 1 7 ) . Methane (F ig . 7 ) and e thane , t h e most impor tan t hydropyrolys is products a f t e r t a r , are suppressed by addi- t i o n of c a l c i t e o r sha le . Carbon d iox ide y i e l d s a r e s t r o n g l y enhanced by t h e calcium minera ls (F ig . 8) . The c a l c i t e - p r e t r e a t e d sample i n t h i s ca se w a s d i f f e r e n t from the one used f o r py ro lys i s i n He, and contained on ly 14.55%; by weight CaC03.

37

DISCUSS I O N

The most s t r i k i n g p o i n t brought ou t i n t h i s s tudy is t h e v a r i a t i o n i n c a t a l y t i c a c t i v i t y e x h i b i t e d by the d i f f e r e n t minera ls p re sen t i n coa l . The c l a y s , which might be expected t o show hydrocarbon cracking a c t i v i t y due t o t h e i r s o l i d a c i d i t y , have v i r t u a l l y no e f f e c t on t h e py ro lys i s y i e l d s t r u c t u r e . The reduct ion i n l i q u i d hydrocarbon y i e l d s by k a o l i n i t e (Fig. 5 ) might be a t t r i b u t a b l e t o secondary c racking of t h e s e compounds by t h i s c lay . The degree of r educ t ion is, however, too small t o determine t h e products of t h i s pos tu l a t ed c racking . I t i s n o t i m e d i a t e l y c l e a r why k a o l i n i t e would c rack l i g h t l i q u i d s and not c rack tar (F ig . 3 ) . One poss ib l e explana t ion i s t h e relative ease of a c c e s i b i l i t y of t h e l i g h t e r l i q u i d s t o the pore s t r u c t u r e of t h e c l a y where m o s t o f i t s a c t i v e s u r f a c e area l ies . The r educ t ion i n methane y i e l d s by s h a l e i n hydropyro lys i s (Fig. 7 ) i s not e a s i l y expla ined . Clays have been shown t o r e t a r d t h e r a t e of CH of cha r s ( 2 0 ) . from those of r a p i d hydropyrolys is , a common under ly ing mechanism f o r CH suppress ion might be p re sen t . K a o l i n i t e and ac id - t r ea t ed montmor i l lon i te reduce tar y i e l d s i n hydropyrolys is (17), whi le montmor i l lon i te does no t . The c l a y s thus s e e m t o show some hydrocracking a c t i v i t y , which is poss ib ly dependent on t h e i r s o l i d a c t i v i t y .

p roduct ion i n slow hydrogas i f i ca t ion While t h e r e a c t i o n s i n tkat system are s u b s t a n t i a l l y d i f f e r e n t

y i e l d 4

I ron - su l fu r mine ra l s , p y r i t e and FeS04, a l s o have l i t t l e in f luence on p y r o l y s i s behavior . The i r on ly s i g n i f i c a n t e f f e c t on py ro lys i s i n H e is t o reduce C H 4 y i e l d s (F ig . 4 ) . o f t h e o t h e r l i g h t hydrocarbon products are a f f e c t e d by i ron - su l fu r minera l a d d i t i o n . d u c t y i e l d s is ve ry s u r p r i s i n g given t h e known a c t i v i t y of t hese minera ls f o r hydro l ique fac t ion . Weller et&. ( 2 1 ) d i d show t h a t a p y r i t e sample t h a t s t r o n g l y enhanced l i q u e f a c t i o n a t 250 a t m H p re s su re had no e f f e c t on l ique- f a c t i o n a t 69 a t m H., t h e p re s su re used i n $he p resen t s tudy . e f f e c t f o r i ron-su lgur c a t a l y s i s of c o a l hydrogenation might thus be ind ica t ed . The pos tu l a t ed a c t i v e s p e c i e s f o r c o a l hydrogenation i n t h e presence of i ron- s u l f u r minera ls i s p y r r h o t i t e . The precise s to ich iometry of t h e p y r r h o t i t e formed w i l l be a f u n c t i o n of t h e hydrogen p res su re ( 2 2 ) , and t h i s s to ich iometry w i l l a f f e c t t h e subsequent a c t i v i t y of t he p y r r h o t i t e (23). Fur ther s tudy of p y r r h o t i t e s to i ch iomet ry and a c t i v i t y as a func t ion of hydrogen p res su re is c l e a r l y needed.

This phenomenon i s d i f f i c u l t t o exp la in a s none

The l a c k o f e f f e c t s of i ron - su l fu r minera ls on hydropyrolys is pro-

A pres su re

The s t rong e f f e c t s of calcium mine ra l s on c o a l p r y o l y s i s are i n s t r i k i n g c o n t r a s t t o t h e comparative l a c k of a c t i v i t y of t h e o t h e r c o a l minera ls . While t h e so l id-ac id c l ays show l i t t l e cracking a c t i v i t y , calcium minera ls reduce t h e y i e l d of v o l a t i l e hydrocarbon products (19). In add i t ion , CaO and CaCO are e s p e c i a l l y a c t i v e i n c racking oxygen f u n c t i o n a l groups t o CO (19) . A l a r g e p o r t i o n o f bituminous c o a l oxygen occurs i n a c i d i c f u n c t i o n a l groups such as phenols or ca rboxy l i c a c i d s , and t h e s t rong ly b a s i c C a O might r e a c t w i th these groups. In a d d i t i o n , w e have poin ted ou t prev ious ly (19 ) t h a t t he r e a c t i o n s by which phenol decomposes homogeneously t o CO would be ca ta lyzed by a s o l i d base. a l s o been shown t o c r a c k over C a O ( 2 4 ) . f l u e n c e t h e decomposition of c o a l oxygen t o a g r e a t e r degree than would o the r a d d i t i v e s . It a l s o appears t h a t s o l i d bases , or a t least CaO, a r e good c a t a l - y s t s f o r c racking aromat ics o r o t h e r c o a l hydrocarbon v o l a t i l e products (19 , 24). S ince CaCO , which decomposes t o CaO dur ing py ro lys i s , i s t h e only coa l mine ra l which g e a e r a t e s a s o l i d base , i t is t h e c o a l minera l w i t h the s t r o n g e s t i n f luence on c o a l p y r o l y t i c behavior.

Non-acidic oxygen f u n c t i o n a l groups such as fu rans have Thus s t rong bases would seem t o in-

38

The e f f e c t s of calcium minera ls on hydropyrolys is a r e less easily expla ined . Ca lc i t e suppresses CH y i e l d s (Fig. 7 ) i n hydropyrolys is t o about t h e same e x t e n t a s do t h e c l a y s . The same s tudy (20) t h a t showed c l a y s t o reduce char hydrogasi- f i c a t i o n r a t e s a l s o showed c a l c i t e t o reduce those rates. Why these two groups Of minera ls should have t h e same e f f e c t s on c o a l hydrogen r e a c t i o n s i s unc lea r . I t i s noteworthy t h a t whi le c a l c i t e suppresses CHq y i e l d s , CaO does not . cussed below, t h e CaCO presen t i n ca l c i t e -p re t r ea t ed c o a l d id no t decompose t o CaO under hydropyrolysas cond i t ions , and i t s e f f e c t s need no t t h e r e f o r e para l - l e l those of lime.

4

As d i s -

Carbon d ioxide y i e l d s from CaO-pretreated c o a l s hydropyrolyzed i n 69 atm H (Fig. 8) a r e almost i d e n t i c a l t o those from t h e same sample pyrolyzed i n 1 a t m H e a t similar time-temperature h i s t o r i e s (17), and i n bo th cases t h e CO y i e l d s are cons iderably h ighe r than those from demineralized coa l . S ince t fe carbonate conten t of t h e Cawpre t r ea t ed sample was smal l , t h i s excess C 0 2 prob- ab ly r e s u l t s from acce le ra t ed decomposition of an as y e t undetermined c o a l oxygen func t iona l group. Carbon d ioxide y i e l d s from c a l c i t e - p r e t r e a t e d c o a l under 69 a t m H c o n t r a s t s w i th the py ro lys i s behavior of t h i s sample under 1 a t m He (19) where, a t s i m i l a r time-temperature h i s t o r i e s , t h e c a l c i t e i t s e l f had s t a r t e d t o decom-

2 pose. y i e l d s t h a t wereno l a r g e r than those from t h e CaO-pretreated sample, d e s p i t e having 2.75 t i m e s as much C a .

a r e very s i m i l a r t o t h o s e from CaO-pretreated coa l . This s t r o n g l y 2

It is i n t e r e s t i n g t o n o t e t h a t t h e c a l c i t e - p r e t r e a t e d sample gave CO

A s a t u r a t i o n e f f e c t i s probably p re sen t .

There i s no d i f f e r e n c e between p y r o l y s i s y i e l d s of t h e r a w c o a l and t h e demineralized coa l . Since 90% of the n a t i v e minera l matter of t h e c o a l used cons i s t ed of c l ays , p y r i t e , and qua r t z (Table 1) t h i s r e s u l t ag rees w i t h t h e o the r f ind ings of t h i s s tudy as t o t h e r e l a t i v e l a c k of a c t i v i t y of t h e s e min- e r a l s . It a l s o impl ies , however, t h a t t he demine ra l i za t ion technique i t s e l f has no e f f e c t on t h e subsequent py ro lys i s behavior of t h i s bituminous coa l .

CONCLUSIONS

Clays and i ron - su l fu r minera ls have few e f f e c t s on t h e p y r o l y t i c behavior of t h i s bituminous coa l . Calcium minera ls reduce y i e l d s of v o l a t i l e hydrocarbon products , and enhance CO formation. C a l c i t e and s h a l e reduce y i e l d s of CH i n coal-hydrogen r e a c t i o n s , wh i l e ac id - t r ea t ed montmor i l lon i te , k a o l i n i t e , and C a O reduce y i e l d s of tar under t h e s e cond i t ions . I ron-su l fur mine ra l s have few c a t a l y t i c e f f e c t s on c o a l hydropyro lys is a t H p re s su res of 69 a t m .

ACKNOWLEDGEMENTS

2

Frank C a r i e l l o and Robert S te inberg obta ined t h e d a t a on mine ra l - t r ea t ed coa l s . under Contract EX-76-A-01-2295, Task Order No. 26.

F inanc ia l support w a s provided by t h e United S t a t e s Department of Energy,

REFERENCES

1. Anthony D.B. , Howard, J . B . , AIChE J 2, 625 (1976).

2. Suuberg E.M., Peters W.A., Howard J . B . , Lnd. and Eng. Chem. Proc. Des. and Dev. 11, 37 (1978).

3. Suuberg E.M., Peters W.A., Howard J . B . , Proc. 1 7 t h Symp. ( I n t e r n a t i o n a l ) on Combustion 1979 p. 1 1 7 , The Combustion I n s t i t u t e , P i t t sbu rgh , Pa.

39

4.

5.

6 .

7 .

8.

9.

10.

11.

12.

13.

14.

15.

16.

17.

18.

19.

20.

21.

22.

23.

24.

Suuberg E.M., P e t e r s W.A., Howard J . B . , Amer. Chem. SOC. Adv. i n Chem. Ser. - 183, 239 (1979).

Suuberg E.M., P e t e r s N.A. , Howard J . B . , F u e l = , 405 (1980).

Howard H.C., Chemistry of Coal U t i l i z a t i o n , Supplemental Volume, 1963, p.340 Wiley, New York.

Given P.H., EPRI Report No. 207-0-0, 1974 p. A-122.

Mukherjee D.K. , Choudhury P.B., F u e l % , 4 (1976).

Guin J . A . , T a r r e r A.P., P r a t h e r J.W., Johnson D.R., Lee J . M . , Ind. and Eng. Chem. Proc. Des. and Dev. 17, 118 (1978).

Granoff B. , Thomas M.G., Baca P.M., Noles G.T., h e r . Chem. SOC. Div. of Fue l Chem. Prepr . 3 (l), Gangwer J.E., Prasad H . , F u e l s , 577 (1979).

Feldmann H.F., Chauhan S.P., Longanbach J . R . , Hissong D.W., Conkle H . N . , Curran L.M., J e n k i n s D.M., Battelle Columbus Labora to r i e s Report BM1-1986,1977.

Sea r s , J . T , Mural idhara H.S., Wen C.Y. , Ind. and Eng. Chem. Proc. Des. and Dev., 2, 358 (1980) .

Gray, D . , F u e l z , 213 (1978).

P a i n t e r P.C., Coleman M.M., J enk ins R.G., Whang P.W., F u e l = , 337 (1978).

Padia A.S., ScD Thes i s , MIT Dept. of Chem. Eng. 1976.

Frankl in H.D. PhD Thesis, MIT Dept. of Chem. Eng. 1980.

Anthony D.B., Howard J . B . , Meissner H.P., H o t t e l H.C. , Rev. Sc i . Instrum. - 45, 992 (1974).

Franklin', H.D. , P e t e r s W.A., Howard J . B . , Amer. Chem. SOC. Div. of Fuel Chem. Prepr . a (2 ) , 1 2 1 (1981).

Tomita A . , Mahajan O.P., Walker P .L. , Amer. Chem. S O C . Div. of Fuel Chem. Prepr . 2 (11, 4 (1977).

Weller S . , P e l i p e t z M.G., Friedman S. , Storch H . H . , Ind. and Eng. Chem. - 43, 1243 (1950).

Richey W.D., 1 2 t h C e n t r a l Regional Meeting h e r . Chem. S O C . , P i t t s b u r g h , Pa., Nov. 1980.

Montan0 P.A., Granoff B . , F u e l z , 214 (1980).

Mead D . W . , M.S. Thes i s , MIT Dept. of Chem. Eng. 1979.

23 (1978).

40

TABLE 1

CHAPACTERISTICS OF COAL EXWIYED

Proximate Analysis

wt.a i as received)

.Xoisture 2 . 0

Volatile Matter 3 6 . 2

Fixed Carbon' 5 1 . 0

Ash 1 0 . 8

100.0

Petrographic Analysis

wt.% mineral matter free

vitrinite 8 1 . 5

Semi-Fusinite 6 . 0

Fusinite 2 . 5

Micrinite 3.0

Macrinite 1 . 2

Exinite 5 . 2

Resinite 0.6 100.0

Ultimate Analysis

Wt.% fdmmf) wt.a id-)

Carbon 7 1 . 7 4 8 2 . 9 1

Hydrogen 4 . 0 4 5 . 6 5

oxygen. 6 . 2 2 7 . 1 9

Nitrogen 1 . 1 4 1 . 3 2

Organic Sul fur . ' 2 . 5 4 2 . 9 4

tunera1 Matter 1 3 . 4 7

1 0 0 . 0 0 100 .00

M i n e r a l Matter Analysis

wt.a

Kaolinite 13

Calcite 10

Quartz 7

Montmorillonite 1 4

Illite 9

4 5

100

Pyrite. -

* by difference

**calculated from total sulfur 1 5 . 7 7 % by weight dry coal1 and measured pyrite content

TAR1.E 2

MINERnL HATTER ADDITIVES STUDIED

PLOTTING SYMBOL

Kaolinite K

M"ntm"ri1lonite M

Ac id-Treated A Montmorillonite

shale s Pyrite P

Calcite C

ouartz 0

CllEMlCAL

can L

FcSOI F

SOURCE __ Mesa Alta N.MCX. I A P I REF CLAY)

Belle FoUrChC N.D IAPI REF CLAY)

Made in house from above

noundsville W. V R

Moundsville W . V I

Sunterville FLA

not known

UT. P MINERAL IN m E -

OBTAINED FROM TREATED SAMPLE'

Ward's Natural 1 1 . 9 Science Estab.

Ward's Natural 8 . a Science Estab.

1 0 . 2

U.S.G.S. 9 . 6

U.S.G.S. 1 7 . 1

Dixie Line 6 Stone 20.2

Ilarwrd Mineralogy l E . 0 Museum

OBTAINED FROM

Fisher scientific 5 . 9 . '

Fisher Scientific 6 . 7

* Doe8 not include 4.3% minera l matter content of demineralized coal

* * A C L U ~ I mineral in coal was mixture of 74m caioii)2 - 26a caco3

41

n 40[

.\" 30

7 2 0

I 0 L 700 0 9 00 1100 1300 1500

TEMPERATURE - K

F i g u r e 1 T o t a l Y i e l d of Yolatiles and Yield O f t a r from D e m i n e r a l i z e d coal ~ y i o l y s ~ s m 1 .tm q r . 5 3 Poldina-TLme Runs.

2 ::L 700 5 0 900 1100 1300 1500

TEMPERATURE - K

Figure 3 Y i e l d of Tar from P y r o l y s i s O f P r e t r e a t e d Coal In 1 atm He. 5 I Holdinq-Time Tuns.

4.0 - E 35-

.\"

a 2.0 -

LL

I 3.0 - 2.5-

2

I

I 1.5-

1.0

0.5

- -

700 900 1100 1300 I500

TEMPERATURE - K

Figure I Y l e l d Of Methane from P y r o l y e i e O f Pre trea ted C o a l i n 1 atn H E , 5 o Holdxno-Time n u n s .

Figure 2 T o t a l Y i e l d of V o l a t i l e s from P y r o l y s i s of P r e t r e a t e d Coal i n 1 a t n H e . 5 P Holdlno- Tim? Runs.

4 2

1100 1300 1500 01 I ’ ’ l I ’ l J 700 900

TEMPERATURE -K

Fioure 5 Y i e l d of Liqht L i q u i d HydrocarMns from Pyrolysis O f Pretreated Coal in 1 atm He. 5 B HOldlna-Tlme Runs.

0

T

s i q u r e 6 Total Y l e l d Of Yolariles from PyrOlyslS O f DrerreaLed Coal ~n 6 9 atm H2, 0 II H o l d l n q - Tlme Runs.

9-

- - - - - -

l - s -

1100 1300 1500

TEMPERATURE - K Figure 7 Y i e l d of Methane from Pyrolysle O f Pre-

t r e a t e d Coal i n 69 a t m HI, 0 9 Holding- Time Runs.

2.50 I I I I I I I c L

L - E 1 w 1.50 - P 2 X -

1.00 - z 0 - m 5 0.50 - u - -

0 700 900 1100 1300 1500

TEMPERATURE - K

Figure 8 Y l e l d O f Cardon Dioxide from Pyrolyris of P r e t r e a t e d Coal In 69 atm HI, Time Runs.

0 s Holding-

4 3

HYDROGENOPYROLYSIS OF COAL AMD COAL DERIVATIVES

H2

T ( " C ) 485 580 6 5 0 760 850

Char 75 .7 7 0 . 9 6 6 . 7 6 1 . 6 6 0 . 6 O i 1 9 . 5 9 . 2 8 . 8 6 . 4 5 . 5 Gas 9 . 1 10 .2 1 5 . 1 24 .2 28 .3 W a t e r 4 . 4 1 6 . 9 I 8 . 9 1 0 . 1 9 . 2

R. C y p r e s

F a c u l t y o f A p p l i e d S c i e n c e s D e p a r t m e n t o f G e n e r a l C h e m i s t r y

and C a r b o c h e m i s t r y U n i v e r s i t e L i b r e d e B r u x e l l e s

BELGIUM

He

580

75 .0 6 . 4 7 .9 4 . 7

1. INTRODUCTION

C o a l h y d r o p y r o l y s i s i s now d e v e l o p p i n g as one o f t h e t h i r d g e n e - r a t i o n ' p r o c e s s e s f o r c o a l g a s i f i c a t i o n o r p a r t i a l l i q u e f a c t i o n . The a d v a n t a g e s o f c o a l h y d r o p y r o l y s i s a r e : r a p i d p r i m a r y d e v o l a - t i l i s a t i o n o f t h e c o a l , w i t h p r o d u c t i o n o f m o r e v o l a t i l e m a t t e r t h a n w h a t i s d e t e r m i n e d b y s t a n d a r d m e t h o d s ; d e s u l f u r i z a t i o n o f t h e c h a r ; s i m u l t a n e o u s h y d r o c r a c k i n g o f t h e p r i m a r y t a r . G e n e r a l r e v i e w s on t h e s u b j e c t h a v e been p u b l i s h e d r e c e n t l y ( 1 ) ( 2 ) ( 3 ) ( 4 ) P r e s e n t p a p e r d e a l s w i t h t h r e e a s p e c t s o f f i x e d bed h y d r o p y r o l y - s i s : t h e i n c r e a s e d f o r m a t i o n o f m e t h a n e and l i g h t m o n o c y c l i c a r o - m a t i c s and p h e n o l s ; t h e d e s u l f u r i z a t i o n p r o c e s s and y i e l d , w i t h r e g a r d t o t h e c o m p o s i t i o n o f t h e m i n e r a l c o n s t i t u e n t s o f t h e c o a l ; t h e m e c h a n i s m o f t h e r m a l c r a c k i n g o f h y d r o - and p e r h y d r o p o l y c y c l i c h y d r o c a r b o n s .

2 . POSTCRACKING OF T H E P R I M A R Y VOLCITILE MATTER

D u r i n g p y r o l y s i s o f c o a l u n d e r H2 p r e s s u r e , t h e p r i m a r y v o l a t i l e m a t t e r a r e s u b m i t t e d t o h y d r o c r a c k i n g . T h i s p o s t c r a c k i n g i s shown b y t h e v a r i a t i o n , c o m p a r e d t o w h a t h a p p e n s i n i n e r t a t m o s p h e r e , o f t h e m e t h a n e c o n c e n t r a t i o n i n t h e gas and o f t h e l i g h t a r o m a t i c s (B .T .X . : b e n z e n e , t o l u e n e a n d x y l e n e ) and p h e n o l s (P .C.X. : p h e - n o l , c r e s o l s a n d x y l e n o l s ) i n t h e l i q u i d p h a s e .

E x p e r i m e n t s h a v e b e e n made w i t h a 32,8% V . M . c o a l f r o m B e r i n g e n , s i z e d < 5 0 0 pm, b e t w e e n 480 a n d 850°C a t a f i x e d H Z p r e s s u r e o f 30 b a r . One r u n was made w i t h 30 b a r He p r e s s u r e a t 580°C. R e s i d e n - c e t i m e o f c a r r i e r g a s was a b o u t 6 0 s . Y i e l d s i n g a s , o i l , w a t e r a n d c h a r a r e g i v e n i n t a b l e I.

~~ ~ ~~~

T a b l e I : Y i e l d s ( 7 : m a f ) ( 3 0 b a r H Z p r e s s u r e )

Above 7 O O 0 C , c o a l d e v o l a t i l i s a t i o n i s h i g h e r t h a n t h e v o l a t i l e m a t t e r c o n t e n t , d e t e r m i n e d f o l l o w i n g s t a n d a r d m e t h o d s .

H y d r o g e n p r e s s u r e i n f l u e n c e a t 580°C b e t w e e n 1 a n d 50 b a r h a s b e e n s t u d i e d o n t h e same c o a l . Y i e l d s o b t a i n e d a r e g i v e n i n t a b l e 1 1 .

44

i

H e pressure-bar

Char oi 1 Gas Water

T a b l e I 1 : Y i e l d s ( % ma:') a t 580°C

He H Z 0 10 20 30 50 30

76 .6 7 2 . 4 7 0 . 6 7 0 . 9 6 9 . 0 7 5 . 0 7 . 4 1 0 . 3 9 . 8 9 . 2 8 . 9 6 . 4 5 . 3 1 0 . 0 1 0 . 3 1 0 . 2 9 . 9 7 . 9 5 . 3 6 . 0 7 . 0 6 . 9 6 . 1 4 . 7

F i g . 1 g i v e s t h e v a r i a t i o n o f CH4 and C H6 c o n t e n t i n t he g a s a t 30 b a r H Z p r e s s u r e compared w i t h c o n v e n z i o n a l c a r b o n i s a t i o n , a s a f u n c t i o n of t e m p e r a t u r e . CH4 c o n t e n t i n c r e a s e s f rom 45% a t 500°C t o 80% a t 850°C. Under c o n v e n t i o n a l a t m o s p h e r i c c a r b o n i s a - t i o n t h e k n o w n r e v e r s e e v o l u t i o n o c c u r s . C H 4 f o r m a t i o n i s d u e t o h y d r o d e a l k y l a t i o n o f h i g h e r h y d r o c a r b o n s . The change i n c o m p o s i t i o n o f B . T . X . , P . C . X . and n a p h t h a l e n e s i s g i v e n on f i g . 2 a s a f u n c t i o n of c a r b o n i s a t i o n t e m p e r a t u r e . L i g h t a r o m a t i c s a r e s t e a d i l y i n c r e a s i n g . P h e n o l s , on t h e c o n t r a - r y , a r e a t t h e i r h i g h e s t c o n c e n t r a t i o n i n t h e low t e m p e r a t u p e o i l . P h e n o l s d e h y d r o x y l a t i o n o c c u r s o n l y above 700°C. Water con- t e n t shows a n i n c r e a s e p a r a l l e l t o t h e d e c r e a s e of P . C . X . (phe- n o l , c r e s o l s , x y l e n o l s ) c o n t e n t . The speed o f c r e s o l s d i s a p p e - a r a n c e i s e q u a l t o t h e s p e e d of t h e i r f o r m a t i o n by d e a l k y l a t i o n of t h e x y l e n o l s . Phenol i n c r e a s e i s a r e s u l t o f b o t h p r o c e s s e s . The o p t i m a l phenol p r o d u c t i o n i s a t a b o u t 750°C. The d e h y d r o - x y l a t i o n o f P . C . X . c o n t r i b u t e s t o t h e B . T . X . i n c r e a s e be tween 600 and 800°C. N a p h t h a l e n e s y i e l d s a r e i n c r e a s i n g w i t h t e m p e r a t u r e a s a r e s u l t o f known f o r m a t i o n of d i - and p o l y c y c l i c a r o m a t i c s f rom c r a c k i n g f r a g m e n t s . Under hydrogen p r e s s u r e t h e s e r e a c t i o n s a r e m a r k e d l y slowed d o w n b u t n e v e r t h e l e s s s t i l l p r e s e n t . F i g . 3 shows t h a t , f o r t h e l i g h t a r o m a t i c s , hydrogen p r e s s u r e i n f l u e n c e a t 580°C i s i m p o r t a n t be tween 1 and 20 b a r . T h i s i s n o t t h e c a s e f o r t h e p h e n o l s . N a p h t h a l e n e s i n c r e a s e w i t h t h e p r e s s u r e f rom 1 , 2 % a t 1 b a r t o 3 , 6 % a t 50 b a r .

3 . DESULFURIZATION OF THE C O A L DURING HYDROGENOPYROLYSIS I t i s known t h a t h igh t e m p e r a t u r e h y d r o p y r o l y s i s l e a d s t o p a r - t i a l l y d e s u l f u r i z e d c h a r . I n t h i s p a p e r , t h i s h y d r o d e s u l f u r i z a - t i o n was c o n s i d e r e d r e g a r d i n q t h e n a t u r e of t h e s u l f u r o u s mine - r a l s p r e s e n t i n t h e c o a l .Asan exemple a high S c o n t a i n i n g i t a l i a n c o a l was s u b m i t t e d t o a f i x e d bed h y d r o c a r b o n i s a t i o n a t 30 b a r

!:r;te i s r e d u c e d by H 2 t o an e x t e n t d e p e n d i n g m a i n l y upon p y r o - l y s i s t e m p e r a t u r e . The r e d u c t i o n of p u r e p y r i t e and m i x t u r e s o f p y r i t e a n d pitch coke under hydrogen p r e s s u r e h a s been s t u d i e d by t h e r m o g r a v i m e t r y be tween 1 and 50 b a r u p t o 950°C. I t can be s e e n o n ' f i g . 4 t h a t t h e f i r s t l o s s of S , c o r r e s p o n d i n g t o t h e c o n v e r s i o n of FeS2 t o FeS, ( p y r r h o t i t e ) i s c o m p l e t e a round 500°C. The r e d u c t i o n t o Fe i s o n l y c o m p l e t e a t much h i g h e r t e m p e r a t u r e . A t 950"C, unde r 50 b a r , t o t a l r e d u c t i o n i s a c h i e v e d w i t h i n 10 m i n u t e s , whereas a t 1 b a r , i t needs 40 m i n u t e s . The same b e - h a v i o u r i s o b s e r v e d f o r p y r i t e i n t h e c o a l . The h i g h e r t h e p y r o - l y s i s t e m p e r a t u r e i s , t h e more i m p o r t a n t i s t h e p y r i t i c s u l f u r e l i m i n a t i o n . Scann ing e l e c t r o n m i c r o s c o p y p h o t o g r a p h i e s show t h e d i s t r i b u t i o n o f S , Ca and Fe i n t h e c o a l and i n t h e c h a r . The p y r i t i c s u l f u r

r e s s u r e . Expe r imen t s were pe r fo rmed a t 580"C, 700" and 8 5 0 " . .

45

i s w e l l l o c a l i s e d i n t h e c o a l w h e r e a s t h e o r g a n i c s u l f u r i s u n i - f o r m e l y d i s t r i b u t e d i n t h e b u i k o f t h e s a m p l e . The c a l c i u m con- t e n t o f t h i s i t a l i a n c o a l i s h i g h , m o s t l y a s CaC03 b u t a l s o some Cas04 ( F i g . 5 ) .

Mo i s tur e Ash (Mf) Volati le Matter ( % Maf)

I n t h e c h a r , a f t e r hydrogen t r e a t m e n t , i t c an be o b s e r v e d o n F i g . 6 t h a t FeS2 h a s been r e d u c e d . A t low t e m p e r a t u r e , r e d u c t i o n i s l i m i t e d t o p y r r h o t i t e ( F e S x ) , a t h i g h t e m p e r a t u r e , t o i r o n . B u t where Ca i s d e t e c t e d i t i s a s s o c i a t e d w i t h S , p r o b a b l y i n t h e f o r m o f Cas and some unreduced CaSO4. The e x p e r i m e n t a l r e - s u l t s a r e summar ized i n t a b l e 1 1 1 . They show i n t h i s c a s e of a h i g h c a l c i u m c o n t a i n i n g c o a l , t h a t t h e h i g h e r t h e p y r o l y s i s tem- p e r a t u r e i s , t h e more s u l f u r r e m a i n s i n the c h a r . I t seems t o be due to i n c r e a s e d d e c o m p o s i t i o n of CaC03 i n t o CaO, which i s more a c t i v e t o f i x t h e v o l a t i l e s u l f u r compounds. CaC03 f rom t h e a s h would have t h e same e f f e c t u n d e r h y d r o c a r b o n i s a t i o n c o n d i t i o n s , a s l i m e s t o n e o r d o l o m i t e , added t o c o a l , i n c o m b u s t i o n , a s t o r e d u c e a t m o s p h e r i c S O 2 p o l l u t i o n . As a c o n c l u s i o n o f t h i s , i t can be s a i d t h a t h i g h c a l c i u m c o n t a i n i n g c o a l s , w i l l n o t be d e - s u l f u r i z e d i n t h e same r a t i o a s p y r i t i c c o a l s a n d t h a t an i n - c r e a s e o f t h e i r h y d r o c a r b o n i s a t i o n t e m p e r a t u r e w i l l l e a v e more s u l f u r i n t h e c h a r .

6,O C 63,24 S , p y r i t i c 0,83 12,9 H 3,71 su l f a t e 0,05 56,4 0 1 4 , l l organic 3,57

N 1,77 S 4,45 A s h 12,9

Total 100,28 Total 4,45

S U L C I S C O A L I

34,l

59,l 790

I Proximate ana lys i s I Ultimate analysis (Mf)

35,6

58,4 690

~ ~ ~ ~ ~ _ _ _ _ _

T"C

Devola t i l i sa t ion (% Maf) Gas O i 1 Water Char

S balance in Char O i l Gas

14,8 16,4 18,8 48,4 38,9

850

61,9 39,7 8,2

14 , l 38,l

41,9 4,7

53,4

Tab le I 1 1 : S u l c i s c o a l and c h a r s .

T H E R M A L CRACKING OF DI- A N D POLYHYOROAROMATICS AT ATMOSPHERIC PRESSURE OF INERT G A S I n c o n n e c t i o n w i t h t he h i g h c o n t e n t o f h y d r o p o l y a r o r n a t i c conpounds p r e s e n t i n c o a l 1 i q u i d s - p roduced by s e v e r a l i n d u s t r i a l p r o c e s s e s , due t o p a r t i a l h y d r o g e n a t i o n , t h e t h e r m a l c r a c k i n g i n i n e r t g a s

46

a t a t m o s p h e r i c p r e s s u r e o f d i - a n d p o l y c y c l i c compounds, p a r t i a l - l y and t o t a l l y h y d r o g e n a t e d was s t u d i e d i n v i e w o f t h e i r c o n v e r - s i o n t o m o n o c y c l i c a r o m a t i c h y d r o c a r b o n s .

K o r o s i ( 5 ) has shown t h a t s t e a m c r a c k i n g o f d e c a l i n e , w i t h a s t e a m t o h y d r o c a r b o n r a t i o n of 1 6 / 1 a t 854°C a n d n e a r l y a t m o s p h e - r i c p r e s s u r e l e a d s t o 18 W % b e n z e n e a n d u p t o 19 W % C2H4 i n t h e g a s p h a s e . We made. t h e r m a l c r a c k i n g a t a t m o s p h e r i c p r e s s u r e i n i n e r t gas and w i t h o u t a n y c a t a l y s t o f t h e f o l l o w i n g d i - a n d p o l y c y c l i c compounds: l , Z - d i h y d r o n a p h t h a l e n e , 1,2,3,4-tetrahydronaphthalene ( t e t r a l i n e ) , d e c a h y d r o n d p h t h a l e n e ( d e c a l i n e ) , 1- a n d 2 - n a p h t o l s , 1 , 2 , 3 , 4 - t e t r a - h y d r o - 1 - n a p h t o l , 5,6,7,8-tetrahydro-l-naphtol, c i s d e c a h y d r o - l - n a p h t o l , p e r h y d r o i n d a n e , p e r h y d r o f l u o r e n e , p e r h y d r o p y r e n e , 9 , 1 0 - d i h y d r o p h e n a n t h r e n e , 1,2,3,4,5,6,7,8-octahydrophenanthrene, p e r h y d r o p h e n a n t h r e n e a n d p h e n a n t h r e n e . The e x p e r i m e n t a l d e v i c e s a n d r e s u l t s of some o f t h o s e s t u d i e s were a l r e a d y p u b l i s h e d ( 6 , 7 , 8 , 9 ) .

C o m p a r i s o n b e t w e e n B .T .X . a n d e t h y l e n e y i e l d s o b t a i n e d b y t h e r m a l c r a c k i n g o f t e t r a l i n e and d e c a l i n e i s g i v e n i n f i g . 7 . I t was de- m o n s t r a t e d t h a t c r a c k i n g m e c h a n i s m o f p a r t i a l l y h y d r o g e n a t e d n a p h t h a l e n e i s c o m p l e t e l y d i f f e r e n t o f w h a t h a p p e n s w i t h d e c a l i n e . I n t h e f i r s t c a s e t h e m a i n c r a c k i n g r e a c t i o n i s d e h y d r o g e n a t i o n l e a d i n g b a c k t o n a p h t h a l e n e ( E q u a t i o n 1 ) . Two o t h e r p a t h w a y s , l e s s i m p o r t a n t , o c c u r a t t h e same t i m e . T h e y c a n e x p l a i n t h e f o r - m a t i o n o f i n d e n e and o f t h e s m a l l a m o u n t s o f m o n o c y c l i c a r o m a t i c ( E q . 2 and 3 ) .

a"m 1) Main r e a c t i o n

J reac t i ons I

F o r t h e p e r h y d r o c o m p o u n d s , o n t h e c o n t r a r y , t h e m a i n r e a c t i o n i s t h e o p e n i n g o f o n e o r t w o c y c l e s w i t h f o r m a t i o n o f a l k y l m o n o c y - c l i c compounds whose s u b s e q u e n t d e h y d r o g e n a t i o n g i v e s t h e c o r r e s - p o n d i n g a r o m a t i c s . A t t h e same t i m e , C2H4 a n d H p a r e t h e m a j o r c o n s t i t u e n t s o f t h e gas p h a s e . S m a l l e r amoun ts o f 1,3-C4Hg, 1 , 7 - o c t a d i e n e , C3Hg and C4H8 a r e a l s o o b s e r v e d . I t was shown i n p r e v i o u s w o r k t h a t t h e l i g h t o l e f i n e s r e a c t t o g i v e b e n z e n e a n d t o l u e n e a b o v e 750°C ( 1 0 , 1 1 , 1 2 ) .

-E R 02"- B.T.X. '34 9 C2H4 9 C3Hg >C4Hg / A R' a '-- 1,7-octadiene, I C2H4

I

Perhydrogena ted \ R OL :&- B.T.X.

47

The i n f l u e n c e o f a n h y d r o x y l g r o u p on t h e r m a l b e h a v i o u r o f d i c y - c l i c compounds w a s s t u d i e d by c r a c k i n g t h e n a p h t o l s , t h e t e t r a - h y d r o n a p h t o l s and d e c a h y d r o - 1 - n a p h t o l . R e s u l t s o b t a i n e d show t h a t t w o c r a c k i n g rnechanismes can be c o n s i d e r e d f o r n a p h t o l s . The f i r s t one i s d e c a r b o n y l a t i o n , s i m i l a r t o wha t was d e m o n s t r a t e d t o happen w i t h phenol (13). I n d e n e i s f o r m e d . The s e c o n d one i s a d e h y d r o x y l a t i o n l e a d i n g t o n a p h t h a l e n e . The hydroxy l g r o u p po- s i t i o n has a r e l a t i v e i m p o r t a n c e on t h e c o n t r i b u t i o n of bo th of t hem.

I n t h e c a s e of n a p h t o l p a r t i a l l y h y d r o g e n a t e d , t h e OH g r o u p can be l o c a t e d e i t h e r on t h e a r o m a t i c r i n g o r on the s a t u r a t e d o n e . T h e r e f o r e , t h e r m a l c r a c k i n g of 5,6,7,S-tetrahydro-l-naphtol and 1,2,3,4-tetrahydro-l-naphtol was p e r f o r m e d . The main t h e r m a l d e - g r a d a t i o n r e a c t i o n was , i n t h e f i r s t c a s e , d e h y d r o g e n a t i o n i n t o 1 - n a p h t o l , u n d e r g o i n g s u b s e q u e n t l y t h e a b o v e d e s c r i b e d r e a c t i o n s . B . T . X . a n d C H4 p r o d u c t i o n i s l ow. Those d i f f e r e n t d e g r a d a t i o n pa thways of $,6,7,8-tetrahydro-l-naphtol can be summarized a s f o l l o w :

OH n +co

+H20 i T.X. i

Secondary reactions

Conce rn ing 1,2,3,4- t e t r a h y d r o - 1 - n a p h t o 1 , t he m a i n degracia t i on r e a c t i o n i s a d e h y d r o x y l a t i o n w i t h s u b s e q u e n t d e h y d r o g e n a t i o n i n - t o n a p h t h a l e n e . The p r e s e n c e o f a n hydroxy l g r o u p l o c a t e d on t h e s a t u r a t e d r i n g makes t h e r u p t u r e of t h e C - C bond e a s i e r , i n c r e a - s i n g t h e B . T . X . p r o d u c t i o n . The d i f f e r e n t mechanismes a r e summa- r i z e d a s f o l l o w .

0

\-- B.T.X., C2H4,C0

The m a i n c r a c k i n g r e a c t i o n o f d e c a h y d r o - 1 - n a p h t o l i s s i m i l a r t o t h a t o f d e c a h y d r o - n a p h t h a l e n e : C - C bond r u p t u r e s l e a d i n g t o o l e - f i n e s a n d c y c l o o l e f i n e s , t o g e t h e r , i n t h i s c a s e , w i t h C O e l i m i n a - t i o n . The o b t a i n e d o l e f i n e s g i v e e a s i l y B .T .X . A s e c o n d a r y r e a c - t i o n o f p a r t i a l d e h y d r o g e n a t i o n l e a d i n g t o i n d e n e f o r m a t i o n O C - c u r s s i m u l t a n e o u s l y and e x p l a i n s t h e l o w e r B . T . X . y i e l d c o m p a r e d w i t h d e c a h y d r o n a p h t h a l e n e .

Main r e a c t i o n co

C o m p a r i s o n b e t w e e n B.T .X. and e t h y l e n e y i e l d s o b t a i n e d b y t h e r m a l c r a c k i n g o f t h e h y d r o g e n a t e d n a p h t o l s i s g i v e n i n f i g . 8 .

I t c a n be seen t h a t t h e d i c y c l i c p e r h y d r o c o m p o u n d s l e a d t o much h i g h e r B .T .X . y i e l d s t h a n t h o s e o f t h e p a r t i a l l y h y d r o g e n a t e d p r o - d u c t s . The i n f l u e n c e o f t h e h y d r o x y l g r o u p i s a p p a r e n t when compa- r i n g t e t r a h y d r o n a p h t o l s a n d t e t r a h y d r o n a p h t h a l e n e . The B .T .X . y i e l d o f t h e t w o t e t r a h y d r o n a p h t o l s a r e h i g h e r t h a n t h a t o f t e - t r a h y d r o n a p h t h a l e n e . The h y d r o x y l p o s i t i o n has a l s o a m a r k e d e f - f e c t . L o c a t e d o n t h e s a t u r a t e d r i n g , t h e B . T . X . y i e l d i s h i g h e r t h a n when t h e OH g r o u p i s on t h e a r o m a t i c r i n g . D e c a h y d r o n a p h t o l g i v e s a g a i n h i g h e r B . T . X . y i e l d b u t , d u e t o a s e - c o n d a r y d 2 h y d r o d e c a r b o n y l a f i o n r e a c t i o n , i t r e a c h e s 2 4 w % a g a i n s t 34 W % f o r d e c a h y d r o n a p h t h a l e n e . As p o l y c y c l i c model s u b s t a n c e s , h e n a n t h r e n e and 3 h y d r o g e n a t e d d e r i v a t i v e s ( d i - , o c t a - and p e r i y d r o p h e n a n t h r e n e ) , p e r h y d r o f l u o - r e n e , p e r h y d r o i n d a n e a n d p e r h y d r o p y r e n e h a v e been c r a c k e d i n t h e same c o n d i t i o n s . D e t a i l e d r e s u l t s a r e a v a i l a b l e b u t n o t g i v e n i n t h i s p a p e r f o r l a c k o f t i m e . The maximum y i e l d s o f B .T .X. and e t h y l e n e . . a r e g i v e n f o r a l l o f t h e m i n t a b l e I V . I t c a n be s e e n t h a t a l l t h e p e r h y d r o c o m p o u n d s g i v e e x c e l l e n t y i e l d s o f m o n o c y c l i c a r o m a t i c s and o f e t h y l e n e , w h e r e a s t h e c o r - r e s p o n d i n g p a r t i a l l y h y d r o g e n a t e d compounds show p r e d o m i n a n t l y d e h y d r o g e n a t i o n , l e a d i n g b a c k t o t h e a r o m a t i c s t a r t i n g h y d r o c a r - b o n . The h y d r o g e n s a t u r a t i o n o f a l l t h e p o l y c y c l i c compoundsmen- t i o n e d , e v e n i n t h e c a s e o f p y r e n e w i t h h i s 4 c o n d e n s e d a r o m a t i c r i n g s , weakens t h e C - C b o n d s . I t makes p o s s i b l e t h e r u p t u r e o f t h e c y c l e s , w i t h l i g h t o l e f i n e s p r o d u c t i o n . Above 750°C, t h e y c o n t r i b u t e t o a n a d d i t i o n a l b e n z e n e f o r m a t i o n as d e m o n s t r a t e d i n e a r l i e r w o r k .

49

B . T . X . 1 , l 3,8 - 239

'ZH4

OH &$

m

B . T . X .

C2H4

34,O

18,9

23,9 17,6

38,3

18

33,6 - 15 30,2 33

&y 27,3

17

T a b l e IV : Optimum B.T.X. and C2H4 y i e l d s ( i n h'% o f i n j e c t e d compounds) o b t a i n e d by t h e r m a l c r a c k i n g o f d i - and p o l y h y d r o a r o m a t i c s .

50

A s t o show i n w i c h p o s i t i o n o f t h e s t a r t i n g m o l e c u l e , c r a c k i n g o c c u r s f i r s t , t o l y c y c l i c compounds l a b e l l e d i n s p e c i f i c p o s i t i o n w i t h I 4 C a n d H h a v e b e e n u s e d . The r a d i o a c t i v i t y o f t h e c r a c k i n g p r o d u c t s i s m e a s u r e d b y r a d i o c h r o m a t o g r a p h y . P h e n a n t h r e n e and p e r h y d r o p h e n a n t h r e n e a r e a b e l l e d i n p o s i t i o n 9 w i t h j H , a n d i n p o s i t i o n s 9 and 1 0 w i t h l i C .

The r a d i o a c t i v e 3H o r 1 4 C c o n t e n t i n t h e c r a c k i n g p r o d u c t s i s e x - p r e s s e d as : molar s p e c i f i c a c t i v i t y o f a g iven compound molar s p e c i f i c a c t i v i t y o f the s t a r t i n g l a b e l l e d compound

i n jmCi/mmole! m C i /mmol e

14 C r a _ c _ k _ ~ n g - - o _ ~ - P ! e ~ ~ ~ ~ ~ - ~ ~ ~ ~ - e!- B n i -0 f - E! h e ! B n t h r e ne - Is_ I ! 0 - - c T a b l e V g i v e s c o m p o s i t i o n and t r i t i u m c o n t e n t o f t h e c r a c k i n g p r o - d u c t s .

C o m p o s i t i o n ( M % )

C75OC/2S I 89O0C/2S I 900°C/2s Gas phase

Hydroger! Methane E t hy 1 ene Ethane Acetylene Propene

3H c o n t e n t

875"C/2s I 890°C/2s

L i q u i d phase

Genzene Indene Naphtha1 ene F1 uorene Phenanthrene Pyrene

92,3 733 093 0,07

T r . T r .

93,6 6 $ 2 0 9 2 0,03

T r . T r .

850°C/2,5s 1 875"C/2s

0,57 0,99 0,77 0,39 1,02 -

0,27 0,85 0,51 0,66

875OC/2s

- 0,47 0,90 0,32 1 1,70

9oooc/2s

0,21 0,76 0,39 0,57

T a b l e V : C o m p o s i t i o n a n d t r i t i u m c o n t e n t o f c r a c k i n g o f p h e n a n t h r e n e 9-3H

The t r i t i u m c o n t e n t i n h y d r o g e n i s h i g h e r f o r low c r a c k i n g y i e l d . T h i s means t h a t t h e r e i s p r e f e r e n t i a l r u p t u r e o f C - H bond i n p o - s i t i o n 9 . T h i s i s i n a g r e e m e n t w i t h w h a t i s a d m i t t e d i n l i t t e r a - t u r e w h e r e B e c k w i t t a n d Thompson ( 1 4 ) g i v e t h e f o l l o w i n g r e a c t i - v i t y p o s i t i o n s e q u e n c e i n p h e n a n t h r e n e : 9 > 1 > 3 = 2 . S l i t h i n c r e a - s i n g p y r o l y s i s t e m p e r a t u r e t h e f o r m a t i o n o f 1 - p h e n a n t h r y l r a d i c a l and e v e n 2 - and 3 - p h e n a n t h r y l r a d i c a l s l e a d s t o a r e d u c t i o n o f 3H c o n t e n t i n h y d r o g e n . The 3H c o n t e n t o f m e t h a n e i s h i g h , w h a t d e m o n s t r a t e s a n i m p o r t a n t c o n t r i b u t i o n o f t h e 3H l o c a t e d o n C9. C r a c k i n g o f p h e n a n t h r e n e -9 ,1014c a t 885°C g i v e 1 4 C c o n t e n t o f 0 ,39 i n CH4, 0 ,52 i n n a p h t h a l e n e , 0,5 i n f l u o r e n e a n d 1 f o r t h e u n c r a c k e d p h e n a n t h r e n e . The f l u o r e n e and m e t h a n e f o r m a t i o n , t h e o n l y c o n s i d e r e d h e r e , s t a r t s w i t h t h e e l i m i n a t i o n o f o n e C and t w o H i n p o s i t i o n 9 . The h y p o t h e t i c a l i n t e r m e d i a t e w o u l d be a f l u o r e n y l b i r a d i c a l .

51

T = l = 0,37)

14c = 0,5 14C = 0,5 T = 0,37 T = 1,37

Measured : I4C = 0,51 14C = 0,4 and 0,48 T = 0,33 T = 1,16

The i n t e r m e d i a t e f l u o r e n y l b i r a d i c a l i s h y d r o g e n a t e d b y t h e h y - d r o g e n o f t h e g a s p h a s e , whose t r i t i u m c o n t e n t i s 0 ,37 . Thus , t h e t h e o r e t i c a l t r i t i u m c o n t e n t o f t h e f l u o r e n e s h o u l d be 0 , 3 7 , as 1 m o l e H 2 i s n e e d e d . The m e a s u r e d v a l u e s a r e i o . v e r y good a g r e e m e n t w i t h t h i s as 3H c o n t e n t f o u n d was 0 3 3 and 1 4 c 0 , 5 1 . F o r CH , measured c o n t e n t was 1,16 f o r 3H, a n d 0 ,4 -0 ,48 f o r I 4 C . The : :C jT b i r a d i c a l h a s t a k e n o n e o f t h e t w o r a d i o a c t i v e c a r b o n and a'yl t h e t r i t i u m . H i s 14C c o n t e n t i s 0,5 and 3H c o n t e n t 1. H y d r o - g e n a t i o n o f ::CHT t o ::CH3T needs one m o l e H whose 3H c o n t e n t i s a g a i n 0,37. T h u s , t h e t o t a l c o n t e n t i s 1 , 3 ? . T h i s v a l u e i s t o compare w i t h 1,16 m e a s u r e d . T h i s l o w e r v a l u e i s d u e t o t h e f a c t t h a t n o t a l l t h e C H 4 i s o r i g i n a t e d i n t h i s way.

S i m i l a r m e c h a n i s m e s w e r e e l a b o r a t e d f o r some o f t h e o t h e r m i n o r c o n s t i t u e n t s o f t h e l i q u i d p h a s e : n a p h t h a l e n e and b e n z e n e . They w i l l be a v a i l a b l e i n m o r e d e t a i l e d p u b l i c a t i o n s .

14 - crackl?s-of-eerhrdroehenanthrene_rs,lo__c T a b l e V I shows t h e c o m p o s i t i o n , y i e l d s o f c r a c k i n g g a s e o u s and l i q u i d p h a s e s , a n d t h e r e s p e c t i v e 14C c o n t e n t o f t h e c r a c k i n g compounds o b t a i n e d a t 750°C and 2s f o r p e r h y d r o p h e n a n t h r e n e

E x p e r i m e n t a l r e s u l t s show t h a t no p h e n a n t h r e n e n o r h y d r o p h e n a n - t h r e n e a r e f o r m e d : t h e r e i s no d i r e c t d e h y d r o g e n a t i o n o f p e r h y - d r o p h e n a n t h r e n e as i s o b s e r v e d f o r t h e h y d r o p h e n a n t h r e n e . The C - C r u p t u r e h a p p e n s b e f o r e t h e C - H r u p t u r e . The H 2 p r o d u c - t i o n i s d u e t o s u b s e q u e n t d e h y d r o g e n a t i o n o f t h e m o n o c y c l i c p e r - h y d r 0- o r h y d r c a r oma t i c s .

- 9 , 1 0 1 4 ~ .

52

H2 CH4 C2H4 C2H6 C3H6 C3H8 'qH8

Benzene Toluene E t h y l benzene m,p-xylenes o-xy lene Styrene Naphtha1 ene Perhydrophenant. Other compounds

Compos i tion(M22)

Gas phase

25,7 26,8 32, l

5 $ 8 529 0 $ 4 397

L i q u i d phase

Y i e l d s

(M%)

103,5 109,5 131,l 23,8 24 ,O

1,s 15 , l

14C c o n t e n t

- 0,14 0,12 0,17 0,18

0,36 0,60 0,71 0,74 0,74 0,77 0,87 1

T a b l e V I : C o m p o s i t i o n , y i e l d s a n d 1 4 C c o n t e n t o b t a i f i e d b y c r a c k i n g o f p e r h y d r o p h e n a n t h r e n e - 9 , 1 0 I 4 C ( T O 75OoC, t = 2 s )

C o n s i d e r i n g a l s o t h a t C2 a n d C o l e f i n s a r e d e t e c t e d i n t h e gas p h a s e as s o o n a s t h e c r a c k i n g g e g i n s t w o p o s s i b l e p a t h w a y s c a n be c o n s i d e r e d .

53

The 1 4 C c o n t e n t s o f t h e i n t e r m e d i a t e s p e c i e s a r e i n d i c a t e d . Let us c o n s i d e r benzene and t o l u e n e f o r m a t i o n . Mechanism l ) , f o l l o w e d by dea l k y l a t i o n and d e h y d r o g e n a t i o n o f t h e r e m a i n i n g c y c l e , l e a d s t o i n a c t i v e benzene and a c t i v e C H ( 1 4 C = 0 , 5 ) . Mechanism 2) l e a d s t o a benzene w i t h a 1 4 C c o n t e n t o f 1. The benzene 1 4 C c o n - t e n t measured was 0 , 3 6 . Thus pa thways 1) and 2 ) c o n t r i b u t e r e s - p e c t i v e l y f o r 2 / 3 and 1 / 3 t o t h e benzene f o r m a t i o n . T h i s l e a d s t o t h e c o n c l u s i o n t h a t i n t h i s perhydrocornpound t h e r e i s a p r e f e r e n - t i a l r u p t u r e be tween t h e c a r b o n s , i n 9 a n d 1 0 p o s i t i o n . Fo r t o l u e n e , t h e l 4 C c o n t e n t measu red w a s 0 , 6 , t w i c e t h a t o f b e n - z e n e . T h i s i s i n good a g r e e m e n t w i t h w h a t was s a i d o r t h e ben- z e n e f o r m a t i o n . Pathway 1 ) i s g i v i n g t o l u e n e w i t h I f C c o n t e n t o f 0 , 5 , a f t e r e l i m i n a t i o n o f a C3 r a d i c a l from t h e i n t e r m e d i a t e . Pathway 2 ) g i v e s a s f o r b e n z e n e , t o l u e n e w i t h 14C c o n t e n t o f 1 , a f t e r a C3 and a C4 e l i m i n a t i o n and d e h y d r o g e n a t i o n of t h e c y c l e . C o n s i d e r i n g t h a t a s found f o r b e n z e n e , pa thway 1) c o n t r i b u t e s f o r 2 / 3 a n d pa thway 2 ) f o r 1 / 3 t o the f i r s t s t e p of t h e r e a c t i o n , t h e t h e o r e t i c a l a c t i v i t y o f t o l u e n e s h o u l d be a 1 4 C c o n t e n t o f ( 2 / 3 x 0 , 5 ) t ( 1 / 3 x 1 ) = 0 , 6 6 . a s t o compare w i t h t h e measu red c o n t e n t of 0 ,60 .

Concern ing t h e r a d i o a c t i v i t y i n e t h y l e n e which i s one of t h e ma- j o r p r o d u c t s i n t h e g a s e s , t h e measu red 14C c o n t e n t was 0 , 1 2 . T h i s d e m o n s t r a t e s t h a t e t h y l e n e i s n o t formed by p r e f e r e n t i a l e l i - m i n a t i o n of t h e c a r b o n atom i n t h e 9 p o s i t i o n .

5 . CONCLUSIONS Dur ing h y d r o c a r b o n i s a t i o n of c o a l , t h e main r e a c t i o n below 7 5 O O C i s h y d r o d e a l k y l a t i o n . T h i s makes p o s s i b l e t o o p t i m a l i z e t h e B . T . X . and l o w b o i l i n g p h e n o l s f o r m a t i o n . D e h y d r o x y l a t i o n o f t h e p h e n o l s i s o n l y i m p o r t a n t above 75OOC g i v i n g a n i n c r e a s e i n wa- t e r and a d d i t i o n n a l l i g h t a r o m a t i c s . The oxygen c o n t e n t of the c o a l , c o r r e s p o n d i n g t o t h e hydroxy l g r o u p i s n o t hydrogen c o n s u - ming below 750°C, a s i t i s t h e c a s e a t h igh t e m p e r a t u r e where con- v e r s i o n t o me thane i s t h e Soa l o f t h e p r o c e s s . D e a l k y l a t i o n o f a l k y l p h e n o l s and a l k y l a r o r n a t i c s e x p l a i n s the a l m o s t l i n e a r i n c r e a - s e w i t h t e m p e r a t u r e o f m e t h a n e . Hydrogen p r e s s u r e p r e v e n t s r e a s s o - c i a t i o n of f r e e r a d i c a l s , n o t o n l y i n t h e p y r o l y s i s of c o a l i t s e l f , b u t a l s o i n t h e p o s t c r a c k i n g p r o c e s s . Due t o t h i s f a c t , n a p h t h a - l e n e and o t h e r heavy p o l y c y c l i c a r o m a t i c s y i e l d s r ema in low, compa- r e d t o wha t i s found when c a r b o n i s a t i o n i s pe r fo rmed unde r p r e s s u - r e of an i n e r t g a s . The s u l f u r e l i m i n a t i o n i n t h e c h a r d e p e n d s o f t h e n a t u r e of t h e m i n e r a l c o n s t i t u e n t s of t h e c o a l . CaCO3 and MgCO3 unde r hydrogen p r e s s u r e r e a c t w i t h s u l f u r compounds t o form Cas . Calcium i s n o t a s s o c i a t e d w i t h s u l f u r i n t h e c o a l , e x c e p t f o r some CaS04. B u t i n t h e c h a r , o n t h e c o n t r a r y , c a l c i u m i s combined w i t h t h e s u l f u r . The c o n c e n t r a t i o n of CaC03 i s however n o t s u f f i c i e n t t o f i x a l l t h e s u l f u r . P y r i t i c s u l f u r i s e l i m i n a t e d a t h igh t e m p e r a t u r e . B u t i t seems p o s s i b l e t h a t t h i s s u l f u r i s t r a p p e d o n CaCO . High s u l f u r c o n t a i n i n g c o a l s w i l l o n l y be w e l l d e s u l f u r i z e d u n j e r hy- d r o p y r o l y s i s c o n d i t i o n s i f t h e i r a shes a r e poor i n CaO and MgO. Thermal p y r o l y s i s a t a t m o s p h e r i c p r e s s u r e u n d e r i n e r t g a s demons- t r a t e s t h a t a l l p e r h y d r o p o l y c y c l i c h y d r o c a r b o n s a r e e a s i l y c r a - cked i n t o m o n o c y c l i c a r o m a t i c s a n d e t h y l e n e . The mechanism of t h e r i n q o p e n i n q , i n t h e c a s e of p e r h y d r o p h e n a n t h r e n e , l a b e l l e d w i t h c a r b o n 14 i n 9 and 10 p o s i t i o n , i s a r u p t u r e o f t h e C - c b o n d be tween 9 and 1 0 . T h i s c o n c l u s i o n i s i n good a g r e e m e n t w i t h t h e perhydrocompounds c r a c k i n g r e s u l t s . No f o r m a t i o n of n a p h t h a - l e n e was o b s e r v e d a t low c o n v e r s i o n y i e l d s o f t r i c y c l i c pe rhy- d rocompounds , w h a t would be t h e c a s e i f o p e n i n g of t h e e x t e r n a l r i n g would be t h e main r e a c t i o n p a t h w a y . H y d r o p o l y c y c l i c a r o m a t i c s

54

u n d e r g o m a i n l y d e h y d r o g e n a t i o n l e a d i n g back t o t h e c o r r e s p o n d i n g a r o m a t i c s t a r t i n g compound. The low s t a b i l i t y o f t h e p e r h y d r o p o l y c y c l i c compound makes P o s s i - b l e t o c o n v e r t i n d u s t r i a l l y t h e h y d r o p o l y c y c l i c compounds, a b u n - d a n t i n c o a l l i q u i d h y d r o g e n a t e s , i n t o benzene and e t h y l e n e , two compounds o f m a j o r i m p o r t a n c e i n i n d u s t r i a l o r g a n i c c h e m i s t r y . The p o l y c y c l i c a r o m a t i c s have t o be s a t u r a t e d by a d d i t i o n a l hy- d r o g e n a t i o n t o t h e c o r r e s p o n d i n g pe rhydrocompounds , wich can then be d i r e c t l y c r a c k e d a t 800-850°C f o r 0 , 5 s r e s i d e n c e t ime , i n t o b e n z e n e , e t h y l e n e , m e t h a n e and h y d r o g e n . The p r o c e s s i s h y d r o g e n s e l f s u f f i c i e n t .

T h i s work i s p a r t o f t h e European Community Program o n t h e "Che- m i c a l and P h y s i c a l V a l o r i s a t i o n o f Coa l " Coworkers a r e B.BETTENS, C . B R A E K M A N - D A N H E U X , P . E R E D A E L , S.FURFAR1, F.NINAUVE and T R A N H U U VINH.

REFERENCES 1 ) R . J . B E L T , L . A . BISSETT, R e p o r t ( 1 9 7 8 ) ( D O E ) , MEJC/RI-79/2 2 ) H . D . C O C H R A N , J r

ACS Symp.Se r . ( 1 9 7 9 ) , 110, 37-54 ' 3 ) G . FYNES, W . R . L A D N E R , J .O.H. N E W M A N

t o be p u b l i s h e d i n " P r o g r e s s i n Energy and Combust ion S e r v i c e s " 4 ) R . CYPRES

P r e p r i n t s of t h e C o n t r i b u t i o n t o t h e F i f t h I n t e r n a t i o n a l Confe - r e n c e on Coal R e s e a r c h , Vo l .11 , B - 2 , 23-40 , D i i s s e l d o r f ( 1 9 8 0 )

Am.Chem.Soc.div.Fue1 C h e m . ( 1 9 7 6 ) , 1_1 ( 6 ) , 190-197 5 ) A . KOROSI, H . N . W O E B C K E and P . S . VIRK

6 ) P . E R E D A E L and D . RIETVELDE Fuel ( 1 9 7 9 ) , - 5 8 , 215-218

7 ) P . B R E D A E L and T R A N H U U YINH Fuel ( 1 9 7 9 ) , - 5 8 , 211-214

8 ) C. DELAUNOIS Ann.Mines de B e l g i q u e ( 1 9 7 2 ) , - 2 , 93 -107

9) R . C Y P R E S and P . B R E D A E L Fuel P r o c e s s . T e c h n . ( 1 9 8 0 ) , 3, 297-311

1 0 ) E . GIL-AV, J . S H A E T A Y and F. STECKEL J .Chem.Eng.Data ( 1 9 6 0 ) , 5 , 98-105

11) P . B R E D A E L Ann.Mines d e B e l g i q u e ( 1 9 7 4 ) , 28, 1 - 6

1 2 ) R . C Y P R E S and C . B R A E K M A N - D A N H E U X Ann.Mines d e B e l g i q u e ( 1 9 7 4 ) , 11, 1109-15

13) B . BETTENS and R . CYPRES T e t r a h e d r o n ( 1 9 7 4 ) , 2, 1253-1260

1 4 ) A .L . J . BECKWITT and M.J. THOMPSON J . Chem". S o c . ( 1 9 6 1 ) , 73

55

- H y d r o g e n o p y r o l y s i s a t 3 0 b a r H2pressu r r

1 b a r c o n v e n t i o n a l c a r b o n i s a t i o n

2 8

24

20

16

12

8

4 ,

0

F I G . I : GAS C O M P O S I T I O N A S F U N C T I O N OF __ TEMPERATURE.

W % L i g h t

.

.

.

.

500 600 700 800 900 Tor

28

2 4

20

16

12

8

4

P.C.X

Naphthalenes

0 10 20 30 4 0 50 60 70 80 90 loo& H2

F I G . 3 : B . T . X . A N 0 NAPHTHALENES Y I E L O S AS A __ F U N C T I O N OF H 2 PRESSURE

(WZ O F O I L ) T = 60s , ‘500 urn

0 30 t (min.)

‘L s loss

100

50

0

~. F I G . 4 : R E D U C T I O N OF F e S Z UNDER Hp PRESSURE

56

~. . .*_.__I .... .

. x""I " ' , ..~

Fig.5 : SEM images SULCIS COAL (56,4% VM, 12,9% ASH,

before pyrolysis 1. Coal 2 . S x-ray d i s t r ibu t ion image 3 . Ca x-ray d is t r ibu t ion image 4. Fe x-ray d i s t r ibu t ion image 5. x-ray spectrum

4,45% S t )

57

Fig. 6 : SEM images SULCIS a f t e r Hydrogenopyrolysis 8 5 O O C - 30 bar H p

V

I- 0

M 3

W Lo 0 0 In Lo 4 N N ,-I

59

A N IN-SITU EXPERIMENTAL OBSERVATION AND PREDICTIVE MODEL OF FREE RADICAL FORMATION

U N D E R LIQUEFACTION REGIME CON0 I T IONS

BY

L. Petrakis, D. W . Grandy and G . L. Jones Gulf .- Research & Development Company

Pittsburgh, Pennsylvania 15230 P. 0. Drawer 2038

Over t h e past 24 years, there have been many studies of f ree rad ica ls

in coal by e lec t ron spin resonance (ESR) techniques directed towards learning

something about c o a l ' s chemical s t ruc tu re , petrography and geology (1 ) . More

recently, some of the more modern and po ten t ia l ly useful magnetic resonance

techniques such a s EWM)R have been used t o probe the s t ruc ture of coal ( 2 ) .

Beyond providing s t ruc tura l information and being a natural product of coal

metamorphosis, t h e f r ee rad ica ls in coal, espec ia l ly those formed during the

heating of coal, a r e believed to play a key ro l e in l iquefaction and pyrolysis

reactions ( 3 ) .

of l iquefaction process variables on the f r ee rad ica ls in coal a n d t r y to find

what connection f r ee rad ica ls have with l iquefaction, i . e . t o answer the

question: a r e f r e e radicals the key to coal l iquefaction? We have used ESP.

spectroscopy t o study the f r ee radicals in a var ie ty of coals and vacuun-,

pyrolyzed coals (4), f r ee rad ica ls in the various product components frov the

solvent refined coal (SRC-I) process ( 5 ) , a n d the f r e e radicals in a variety of

coal solvent s l u r r i e s reacted under a variety of conditions ( 6 , 7 ) . Coal

macerals, o r the various organic consti tuents of coal analogous t o minerals

i n rocks have a l s o been studied by ESR spectroscopy in our laboratory a f t e r

a variety of pyrolysis ( 6 ) a n d l iquefaction treatments ( 9 ) .

experiments were performed as most have been done in the pas t , i . e . a t room

temperature a f t e r the reactions had t a k e n place.

O u r goal i s t o gain a more complete understanding of the e f f ec t

All of these

Recently we have developed

60

a h igh temperature, h igh pressure ESR c a v i t y t o study t h e f r e e r a d i c a l s i n

coal dur ing l i q u e f a c t i o n (10, 11, 12).

We have used t h i s h igh temperature, h igh pressure ESR c a v i t y f o r

d e t a i l e d study o f the e f f e c t s o f process va r iab les on the f r e e r a d i c a l s i n

Powhatan #5 coal dur ing l i q u e f a c t i o n .

design i n v o l v i n g two l e v e l s each o f temperature (400 and 46OoC), gas (H2 and N2),

pressure (8.2 and 11 MPa), so l ven t ( t e t r a l i n and SRC-I1 heavy d i s t i l l a t e der ived

from Powhatan #5 coa l ) and heat ing time 3 and 15 minutes t o r e a c t i o n tempera-

tu re . Free r a d i c a l spec t ra l parameters were monitored c o n t i n u a l l y from about

2 minutes a f t e r r e a c t i o n temperature was reached, up t o one hour.

f rom t h i s work, t h a t temperature and so l ven t were the two most impor tan t var iab les ,

we proceeded t o study these var iab les i n more d e t a i l , using 400, 425, 400, 450,

460 and 48OoC and t e t r a l i n , naphthalene and SRC-I1 as l i q u e f a c t i o n so lvents .

The data from the study o f process var iab les e f f e c t s and the more d e t a i l e d study

o f temperature and so l ven t e f f e c t s were analyzed w i t h the a i d o f a regress ion

model.

The procedure used was a z5 f a c t o r i a l

A f t e r f i n d i n g ,

Free r a d i c a l measurements on the coal so l ven t s l u r r i e s a re done under

l i q u e f a c t i o n cond i t ions , i .e . i n - s i t u , us ing a h igh temperature, h igh pressure

ESR cav i t y .

p rev ious l y (11, 12) . The c a v i t y system i s b a s i c a l l y a c y l i n d r i c a l brass TEOll

X-band c a v i t y w i t h i n t e r n a l modulat ion c o i l s and i n t e r n a l a x i a l heater i n s i d e

a water-cooled be r ry l i um copper pressure vessel .

OD, 2.5 mm ID quar tz tubes by p lac ing 0.5 g o f Powhatan #5 coal i n the bottom

o f t he tube and i n j e c t i n g 0.5 g o f t e t r a l i n o r SRC-I1 heavy d i s t i l l a t e (SHD).

I n the naphthalene experiments, the coal and naphthalene were premixed a t 1 : l

by weight and then poured i n t o the sample tube.

a thermocouple imbedded i n t h e sample.

The d e t a i l s o f the c a v i t y and i t s opera t ion have been pub l ished

Samples a re prepared i n 4 mm

Temperature measurement i s by

Typ ica l l y , several spectra a re recorded

61

before heating and then continuously from about 4 minutes a f t e r heating

was begun up t o one hour.

r e l a t ive to the signal from a CuS04.5H20 reference on the internal wall

of the cavity.

correction a re outlined in detai l elsewhere (12, 13 ) . Data a re normally

displayed as corrected ( t o 2OoC) spin concentration versus time plots.

S p i n concentration measurements a re made

T h e calculations fo r spin concentration and i t s temperature

About 45 experiments were done using Powhatan #5 coal to screen

the major process var iab les , such as solvent, temperature, gas type,

pressure, a n d heating time. The d a t a from these experiments were used t o

formulate a regression model t o so r t out the major e f f ec t s and t h e i r in te r -

actions (13). Table I sumnarizes the resu l t s of this model. Reaction time

alone was found t o be ins igni f icant .

s ign i f icant variable, accounting fo r about half of the e f f ec t s present in the

model. When so lvent and solvent gas in te rac t ions a re added in with ternpera-

t u re , almost 90% of the variation of the data i s accounted for . Heating time,

pressure and gas type alone o r in combination with temperature have re la t ive ly

minor e f f ec t s on the data.

Temperature was found t o be the most

Based on these observations, i t was decided tha t temperature and

solvent type warranted fur ther investigation. Experiments a t 425, 440, 450

and 48OoC were added as well as a complete s e r i e s of experiments with Powhatan

coal using naphthalene as the l iquefaction solvent.

a t 3 minutes, pressure a t 1600 psig a n d hydrogen was used in a l l of the

additional experiments.

as a function of time f o r the three coal-solvent systems a t 40OoC.

points a r e experimental data and the so l id l i nes a re the spin concentrations

predicted by the regression model. These a re n o t f i t t e d curves. A t time 0 ,

Heating time was fixed

Figure 1 shows the variation of spin concentration

The

62

the s lu r r i e s are unheated.

temperature.

ments i s essent ia l ly the same as the unheated coal and t h a t a l l the SHD and

naphthalene experiments a re somewhat higher. Figure 2 i s a similar plot of

the experimental data a n d predicted spin concentrations a t 48OOC. Here the

spin concentration of a l l three Powhatan coal-solvent s lur ry systems i s much

higher than t h a t of the unheated s lu r r i e s . Again, the same ordering of spin

concentration among the solvent systems i s observed.

spin concentration in the solvents, tetralin<SHD<naphthalene, i s believed t o

be due to the re la t ive hydrogen donor capab i l i t i e s of the three solvents.

Naphthalene i s a pure aromatic and should have no donatable hydrogens.

has four donatable hydrogens and SRC-I1 heavy d i s t i l l a t e , although highly

aromatic, would be expected t o have some donatable hydrogen. Figures 3, 4

a n d 5 are spin concentration versus time plots displaying the data f o r a l l s ix

temperatures used fo r each of the solvents. The naphthalene, Powhatan coal

experimental d a t a , shown i n Figure 3 , shows the general trend t o higher spin

concentration with increasing temperature.

f a l l very close.

a n d 460' d a t a .

than a l l the other d a t a from the lower temperatures.

experiments, shown in Figure 4, show a s imi la r ordering of spin concentration

among the 6 temperatures, however, the values a t the corresponding temperatures

a r e lower than i n the previous figure depicting the naphthalene experimental

data.

t e t r a l i n solvent experiments, has a s imi la r trend o f increasing spin concen-

t r a t ion with temperature, however, the order of the 460 and 48OoC data are

reversed compared t o the other two solvents.

All p o i n t s a t t > O a r e a t the desired experimental

Note t h a t the spin concentration in the t e t r a l i n solvent experi-

The r e l a t ive order of

Tetralin

The data a t 400, 425 and 440'

There i s a similar bunching a t higher values f o r the 450

The spin concentration found a t 480' i s considerably higher

The SHD Powhatan coal

Figure 5, showing p lo ts o f spin concentration versus time fo r the

From these d a t a and a few data

6 3

0 taken under s imi la r conditions a t 470 C , there appears t o be a maximum in

spin concentration around 46OoC in the Powhatan coal t e t r a l i n s lur ry

sys tern.

Discussion and Conclusions

1. I n general , the coal f r e e rad ica ls a r e quenched in following

the order of naphtha leneCSHDdet ra l in .

expectations which a r e based upon the amount of donatable hydrogen present

in the three solvents. The r a t e of f r ee radical formation i s assumed t o be

only temperature dependent .

experiments with coals and coal macerals.

t r a t ion depends on t he competing e f f ec t s of f r ee radical formation and f r ee

radical quenching. The l a t t e r , unlike the former, i s solvent dependent. The

solvent dependency wi l l be determined both by the amount of donatable hydrogen

tha t i s ava i lab le as well as by the ease with which the f r e e radical quenching

hydrogen can be transferred t o the coal f r e e rad ica ls .

This conclusion agrees with our

This i s based on previous extensive pyrolysis

The observed f r e e radical concen-

2. The f r e e radical concentration of the l iquefaction s lur ry gen-

e r a l l y increases with increasing temperature. This i s s t r i c t l y t rue fo r

the naphthalene and SHD experiments and i s followed by the tetra1 in experiments

up t o 46OoC where an apparent maximum i s reached, with the spin concentration

decreasing then a t higher temperatures. The general increase in spin concen-

t r a t ion with temperature i s expected due t o the grea te r thermal energy available

f o r bond breaking. From the resu l t s of the cor re la t ive model, we find t h a t

about half of t h e var ia t ion in the spin concentration i s due t o temperature

alone.

e f f ec t s .

Temperature and solvent in te rac t ions account fo r 70% of the observed

64

3. The s p i n concent ra t ion i s dependent upon reac t i on t ime and t h i s

dependence i s a l so i n f l uenced by so l ven t and temperature.

r e l a t i v e slopes o f t h e s p i n concent ra t ion versus t ime curves, f rom 0.1 t o

1.0 hr. , a re 15, 5 and 0 ~ 1 0 ’ ~ sp ins /g pe r hour f o r t he naphthalene, SHD and

t e t r a l i n experiments, respec t i ve l y , demonstrating the so l ven t dependence. A t

480°, t he s lopes have increased t o 40, 35 and 2 0 ~ 1 0 ~ ~ sp ins /g pe r hour fo r t h e

same th ree solvents.

A t 4OO0C, t h e

4. From t h e r e s u l t s o f t he f u l l c o r r e l a t i v e model, we f i n d t h a t

temperature, so l ven t and residence t ime and t h e i r i n t e r a c t i o n s account f o r

about 90% o f t he e f f e c t s noted i n the f r e e r a d i c a l concentrat ion. Gas type

has some minor s i g n i f i c a n c e as does pressure.

e f f e c t .

Heating t ime has a n e g l i g i b l e

ACKNOWLEDGMENT

This work was performed under Un i ted States Department

of Energy sponsorship, Cont rac t No. DE-ACO-179ET14940. The

authors wish t o acknowledge t h e exper t techn ica l ass is tance

of M r . A. V . Fare r i i n the exper imental aspects o f t h i s work.

65

References

1. H . T. Schamler and E . duRutter i n "Chemistry of Coal Ut i l iza t ion" , Supp. Vol. ( H , H . Lowry Ed.) John Wiley and Sons, Inc. New York, 1963 pp 78-85.

2 . H . L. Retcofsky, M. R . Hough and R . B. Clarkson, ACS Fuel Div. Preprints, V o l . 24, No. 1 , 1979 p 83.

3.

4.

5.

6. L. Pet rak is and D . W . Grandy, ACS Fuel Div. Preprints, Vol. 23, No. 4 ,

R . C. Neavel, Fuel 55, 237 (1976).

L. Pet rak is and D. W . Grandy, Anal. Chem. 3, 303 (1978).

D . W . Grandy and L. Petrakis, Fuel, 58, 239 (1979).

1978 p . 147.

7. L. Pet rak is and D. W . Grandy, Fuel, 2, 227

8. L. Pet rak is and D . W . Grandy, Fuel, 60, 115

9. L. Pet rak is and D . W . Grandy, Fuel, 60, 120

10. L. Pet rak is and D. W . Grandy, Nature

1980).

1981 ) .

1981).

11.

12. L . Pe t rak is , D . W . Grandy, R . G . Ruberto and N . L. Carr, "Fundamentals

D . W . Grandy and L. Pet rak is , J . Mag. Res. 41, 367 (1980).

of Coal Depolymerization", Quarterly Report, DOE/ET/14940-2, NTIS, Springfield, VA 1980.

13. L. Pet rak is and D . W . Grandy, submitted t o Fuel.

66

TABLE I

GENERAL CORRELATION MODEL

** . Fractional

Probability of Fractional Null Hypothesis

Sum of Square Contribution (i.e., term* Variables Effects* of Each Term of Each Term significant)

C1. time. temperature 119455 .480 .0001 C~.time*temperature.solvent 51511 .207 .897 .ooo 1 C2*time*temperature.~olvent*gas 52284 .210 ,0001

C4. time.pressure 8025 .032 .ooo 1 . 000 1 .09,4 Cg*time*temperature*heating rate 6556

C6.time.temperature.gas 4739 .019 C7*time*temperature*pressure.gas 4355 .017

C8.time.pressureoheating rate Cg.timemtemperature.pressure

ClO.time*heating rate Cl1. time

652 .003 565 .002

358 .001 256 .001

. 000 1 . 000 1

.0129 ,0205

.0649

.1184

Total Number of Points = 773; Total Data Sum of Squares = 328302; Total Model Sum of Squares - 248755; Error = 79548; R-Square (Model SOS/Total SOS) = 0.758

* Corrected Spin Concentration = Intercept + Sum of Terms.

** The lower the number, the higher the probability that the variable effects are real.

67

SPIN CONCENTRATION VS. ELAPSED TIME POWHATAN +5 COAL, 1600 Dslg H2. 400'C 3 mln HT

SPIN CONCENTRATION VS. ELAPSED TIME POWHATAN * 5 COAL. le00 psip. 480 C 3 min HT.

. 100, 'b 100

z . 0 NAPHTHALENE '

TETRALIN

, SHD

O o 0 ELAPSED TIME HOURS 1.0

FIGURE I

- 0.0 0.2 0.4 0.6 0.11 1.0

ELAPSED TIME HOURS

FIGURE 2

68

The Cata lys is o f the Exchange Reactions Between T e t r a l i n - d12 and Diphenylmethane by Ino rgan ic Compounds

C.B. Huang, H.-H. K ing and L.M. Stock

Department o f Chemistry U n i v e r s i t y o f Chicago

Chicago, I l l i n o i s 60637

I I n t r o d u c t i o n

An a r ray o f i no rgan ic compounds have been i n v e s t i g a t e d as c a t a l y s t s f o r coal g a s i f i c a t i o n reac t i ons (1 ,2 ) . The pathways by which these compounds a l t e r the r a t e and t h e product d i s t r i b u t i o n s i n the g a s i f i c a t i o n r e a c t i o n have n o t been f u l l y resolved. the i n i t i a t i o n reac t i ons which occur a t the th reshho ld temperatures o r the r a p i d gas forming reac t i ons a t t he h ighe r u l t i m a t e temperatures has n o t been establ ished. the i n f l u e n c e o f i no rgan ic substances on t h e exchange reac t i ons between the hydrogen atoms i n the benzy l i c p o s i t i o n s and the hydrogen atoms i n the

Whether t h e most e f f e c t i v e c a t a l y s t s promote

We sought t o reso lve t h i s p o i n t by an i n v e s t i g a t i o n o f

C6H5CH2C6H5 + Te t ra l i n -d l + C6H5CHDC6H5 + Tetral in-dl,

aromatic p o s i t i o n s . These exchange r e a c t i o n s proceed s low ly a t 400°C i n the

C5H5CH2C6H5 + Te t ra l i n -d12 * C6H5CH2C6H4D + Te t ra l i n -d l

absence o f ca ta l ys ts ( 3 ) . p o r t a n t way t o the breakup o f t he coal s t r u c t u r e du r ing the g a s i f i c a t i o n re - act ions shown f o r the r a d i c a l i n i t i a t e d decomposition o f a 1,3-diphenylpropane:

Both o f these reac t i ons may c o n t r i b u t e i n an i m -

C ~ H ~ C H ~ C H ~ C H ~ C ~ H ~ + R. -t RH + C ~ H ~ ~ H C H ~ C H ~ C ~ H ~

C ~ H $ H C H ~ C H ~ C ~ H ~ -+ C ~ H ~ C H = C H ~ + C ~ H ~ C H ~ .

and phi

the ac id-cata lyzed decomposition o f a diphenylmethane w i t h an e l e c t r o - i c agent, E+

C6H5CH2C6H5 + E+ -+ CH2C6H5

69

In the absence of a ca t a lys t a t 400"C, the f r ee radical exchange reaction between the hydrogen atoms in the benzylic positions occurs much more readi- l y t h a n the exchange reactions of the hydrogen atoms bonded t o the aromatic ring ( 3 ) . Accordingly, we s o u g h t evidence f o r the acceleration of e i ther process i n the presence of inorganic compounds.

Results and Discussion

I n each experiment, diphenylmethane (0.377 mole) and tetralin-d (0.377 mole) and a potential ca ta lys t (0.045 mole) were sealed in a 4?ass reactor a t ambient temperature. The reactor was submerged in a f lu id sand b a t h a t 400°C f o r the desired reaction in te rva l . After cooling, the organic contents of the reactor were separated from the inorganic reagents and analyzed by gas chromatography and nuclear magnetic resonance. The exchange reaction proceeds to give about 15% of the monodeuterio com-

C6H5CH2C6H5 + Tetralin-d12 400°C 3o C6H5CHDC6H5 + Tetralin-dll

15%

pound in 30 minutes in the absence of a ca ta lys t . Lithium, sodium and potassium chloride are ineffectual as expected. Similarly, sodium fluoride, chloride, bromide and su l f a t e did n o t accelerate the exchange reactions. Sodium iodide enhanced the benzylic exchange reaction t o a minor extent ( 2 2 % ) . Iodine and hydrogen iodide accelerate the reaction t o a much greater extent.

Lithium, sodium, and potassium carbonate and sodium and potassium bicarbonate do not enhance the exchange reactions. Thus, none of the a lka l i metal compounds exer t any ca t a ly t i c influence on t h i s exchange reaction a t the threshhold temperature of 400°C.

pounds. enhance the exchange reaction. Calcium and magnesium chloride are also ineffectual ca ta lys t s fo r the exchange reaction a f t e r a 30 minute reac- t ion . 120 minutes suggest t ha t magnesium chloride enhances the r a t e of the exchange of the hydrogen atoms of the aromatic nucleus b u t not the benzylic exchange reaction.

Zinc halides a l so exer t an accelerating influence on the ra te of exchange of b o t h the a l ipha t ic and aromatic hydrogen atoms.

Somewhat s imi la r resu l t s were realized with the alkaline earth com- Neither calcium oxide or carbonate or barium carbonate or oxide

However, our preliminary resu l t s for reactions carried o u t for

70

Compound %D i n Recovered D i phenylmethane

%D i n Recovered T e t r a l i n

A r a A r a B

ZnCl 12 9

Zn12 37 40

54 33 86

40 28 52

Whereas cadmium c h l o r i d e i s i n a c t i v e , compounds such as stannous c h l o r i d e and s tann ic c h l o r i d e s e l e c t i v e l y enhance the r a t e o f exchange o f t he aromatic hydrogen atoms o f diphenylmethane and t e t r a l i n - d a t 400°C. Anhydrous vanadium t r i c h l o r i d e and f e r r i c c h l o r i d e and hydra& chromous c h l o r i d e and hydrated c u p r i c c h l o r i d e e x e r t a s i m i l a r e f f e c t on the r e a c t i o n .

%D i n Recovered %D i n Recovered Diphenylmethane Tetra1 i n Compound

A r ci A r a B

SnCl 19 0 23 91 91

CuCl 2 - 2 H 2 0 24 5 44 92 92

Other h i g h l y r e a c t i v e compounds such as aluminum c h l o r i d e and molybdenum ( V ) c h l o r i d e cause extens ive r e a c t i o n s o f the diphenylmethane and the t e t r a - l i n . Moreover, o x i d i z i n g agents, f o r example, the oxides o f l ead and i ro r ; conver t diphenylmethane t o benzophenone.

suggest t h a t c a t a l y s t s can s e l e c t i v e l y i n i t i a t e f r e e r a d i c a l o r e l e c t r o p h i - l i c decomposition reac t i ons o f many coal molecules. The d i ve rse cha rac te r o f t h e r e s u l t s w i l l be emphasized i n the presentat ion.

The r e s u l t s obta ined a t t he th reshho ld temperature o f 400°C s t r o n g l y

References

(1 ) Johnson, J.L., " K i n e t i c s o f Coal Gas i f i ca t i on , " John Wi ley and Sons, New York, New York (1979).

71

( 2 ) McKee, D.W., "Catalyzed G a s i f i c a t i o n Reactions o f Carbon," i n "Chem- i s t r y and Physics o f Carbon" e d i t e d by P . L . Walker, Jr. and P.A. Thrower. Volume 16, p. 1 (1981).

( 3 ) H.-H. K ing and L.M. Stock, " In f l uence o f I l l i n o i s No. 6 Coal and Coal- r e l a t e d Compounds on the Exchange Reaction Between Diphenylmethane and P e r d e u t e r i o t e t r a l i n , " Fuel, 59, 447 (1980).

72

THE RATE AND THE MECHANISM OF CATALYTIC COAL LIQUEFACTION BY I R O N SULFIDES: PART I .

H :S,RATES OF REACTION AND d C E CONVERSION

BY: A t t a r , A. and M a r t i n , J . B.

THE SYSTEM FeS,

Dept. Chek., Eng. ,.N.C.S.U. , Raleigh, N.C. 27650

INTRODUCTION The systems FeSz-HZ-HzS and FeS2-hydrogen donor-HZS p l a y a c r i t i c a l

r o l e i n the c a t a l y s i s o f coal l i q u e f a c t i o n by n a t u r a l l y occu r r i ng minera ls . Consequently, t he re i s a tremendous i n c e n t i v e t o understand the exact mechanism and r a t e s o f r e a c t i o n which a f f e c t t he c a t a l y s i s o f coa l l i q u e - f a c t i o n by FeS,.

our own labo ra to ry suggest t h a t the dominant c a t a l y t i c a c t i o n i s due t o the formation o f an i n te rmed ia te compound, p o s s i b l y [FeSx+1H2] which can r e a c t according t o t h e scheme:

Examination o f t h e data a v a i l a b l e i n the l i t e r a t u r e and s tud ies from

FeS, + H2S

RR '

RH + R ' H

x+ 1 .-+ FeS

The main f u n c t i o n o f t he FeS hydrogen t o o r g a n i c a l l y boun8+iydrogen, e i t h e r i n the form o f donor molecu les and/or coal de r i ved molecules. r o l e i n t h i s system s ince i t s value determines t h e e q u i l i b r i u m d i s t r i b u t i o n of the a c t i v e c a t a l y t i c in termediate, FeSx+lH2, and the l ess a c t i v e species

FeSx+lThis mechanism exp la ins many o f t h e observat ions i n the system coa l - solvent-FeS2.

1. C a t a l y t i c a c t i o n by Fe s a l t s i s observed on ly when H S i s present i n the reac to r . The l e v e l o f t h e c a t a l y s i s depends 6n t h e r a t i o [ H z S l / [ H z l . Regardless o f t h e s t a r t i n g m a t e r i a l , when the FeS, i s a l lowed t o ca ta l yze the r e a c t i o n long enough, a f i x e d r a t i o o f Fe t o S i s achieved, t y p i c a l l y o f t h e order o f Fe/S 1/1.09. Such a r a t i o cou ld be the r e s u l t o f the thermodynamic e q u i l i b r i u m achieved fo r t he coal a t t h e p r e v a i l i n g [H2SI/[Hz]. The type o f p y r i t e used t o c a t a l y z e the r e a c t i o n i n f l uences main ly t h e r a t e o f t h e i n i t i a l stages o f t he r e a c t i o n b u t has l i t t l e e f f e c t on t h e r e s u l t s o f l ong t ime l i q u e f a c t i o n .

i s t o permi t conversion o f molecular

The [HzS]/[H2] p lays a c r i t i c a l

and FeS,.

The most impor tant f a c t s are:

2.

3.

Since the r a t i o [H.$]/[HzJ (gas) and t h e r a t i o Fe/S ( s o l i d ) p lay such a c r i t i c a l r o l e i n the l i q u e f a c t i o n , i t appeared use fu l t o q u a n t i t i z e t h e r a t e o f t h e i n d i v i d u a l reac t i ons invo lved. To achieve reasonable data, i t appeared e s s e n t i a l t h a t t h e same sample o f FeSz be tes ted so t h a t i t would be poss ib le t o avoid quest ions r e l a t e d t o t h e conversion o f t he sur face and so t h a t small d i f f e rences i n r e a c t i v i t y cou ld be determined. I n t h i s paper p r e l i m i n a r y r e s u l t s are presented on the system FeSx-H2-H2S.

EXPERIMENTAL

surface cond i t i ons , a pulsed d i f f e r e n t i a l r e a c t o r (PDR) was used, s i m i l a r t o t h a t described by A t t a r (1979).

In order t o have more o r l ess t h e same sur face area and t h e same

The on ly d i f f e r e n c e was t h a t a S.S.

73

packed bed reactor 1/4" ID x 1 f t packed with -100+120 mesh FeS particles was used as the reactor. Helium was used as the carrier gas an$ pulses of H2, H2S or CO were used t o investigate the effect of the surface conversion of the pyrite on i t s reactivity, the activation energies f o r the reaction, etc. Figure 1 is a schematic diagram o f the reaction system.

In a typical experiment, a pulse of H2 was injected into the He carr ier and the product pulse, which consists of unreacted H2 and H2S + S2 was separated on a Chromosorb 105 column and the components were determined by a TC detector.

ANALYSIS OF THE DATA

from t h e consumption of the hydrogen, 1 .e. , The relative rate of reaction, r j , in the j - t h pulse was determined

WHO - w 2 H 2 j ri =

where Wo i s theLnumber of moles of H 2 injected and kr,,

moles of incorporated H2. the experiments, in order t o allow the determination of the variations of r . with the temperature. To a f i r s t order approximation, since the sdrface was barely converted in each pulse, one may write, assuming Arrhenius dependence of the rate constant on the temperature:

are the number of H2 The temperature was program6ed during most of

E - - D T I\ I -

r = ko s e [H2] j or roughly: \

E " H 2 j -

win log r = l og [ l - -1 = log ko [H2] - j ( 3 )

L

[HI i s the average concentration of H2 near the surface and E i s the acgivation energy. B and C were done on the same pyrite sample by successive injection of H2 pulses in three cycles of heating and cooling of degassed FeS2. The d a t a indicate t h a t as the surface i s being converted, the activation energy rises s l ight ly , from 26.4 t o 27.4 kcal/mole fo r abou t 1% surface conversion and that the preexponential factor decreases. the accumulation of FeS2- near the surface which resis ts t o the diffusion of S' in the solid (see rgf. 2 ) .

curve E was derived with a specially prepared sample of FeS2. The las t curve indicates that sample D i s a much more reactive specimen, with an activation energy of 22.7 kcal/mole and a larger preexponential factor than the raw FeS2.

FeS,. Fe, S , H2 and H2S in such a system. one of the subsystems, i . e . , FeS2 + H2 and the role of surface conversions in deactivation of the reaction of FeS2 with pure H2 i s demonstrated. Specially prepared samples of FeS2 appear t o have a much larger activity toward H2, and as will be shown in a future paper, much larger catalytic effect on the rate of coal liquefaction.

REFER EN C E S

Attar, A . , Fuel, E, 201 (1978).

Figure 2 shows some of the d a t a obtained. Curves A ,

This i s due t o

Curve D was obtained using a different sample of iron pyrite while

SUMMARY A new mechanism i s proposed for catalytic coal liquefaction using

The mechanism includes many of the observed facts on the role of Preliminary d a t a are presented on

1 . Attar, A . , Rev. Sci. Inst . , 50 ( l ) , 111 (1979) . 2 .

-1 I

z a d

75

/

w / P , , 0 P

0

0

0 0

0

2-l

P &, 0

0

I I I I I

9 c) d ln (0

I (Y I-

9 9 9 ? I

9 I I I I

v 801 = Q, B O 1

76

MODELLING OF LIGNIN THERMOLYSIS +

M.T. K l e i n * and P.S. V i r k

Department o f Chemical Engineer ing Massachusetts I n s t i t u t e o f Technology, Cambridge, !!A 0Z.N

I n t roc! uc ti on

The o b j e c t of t h e present work was t o at tempt il fundamental d e s c r i p t i o n o f l i g n i n the rmo lys i s . Th is was mot ivated by a r e c o g n i t i o n t h a t t he increased use of biomass and low-rank coal resources must be accompanied by an enhanced underztanding of t h e fac to rs which i n f l u m c e t h e i r thermal processif in. o f biomass, and has a d i r e c t e v o l u t i o n a r y l i i i k a c y t o peat and l i g n i t i c coals , i n s i g h t s i n t o i t s t he rmo lys i s should prove r e l e v a n t t o the p r a c t i c a l py ro l yses of bo th biomass and coal .

Our i n v e s t i g a t i o n comprised t h r e e major components. F i r s t , a c r i t i c a l examination o f l i g n i n s t r u c t u r e and chemist ry was undertaken t o d i sce rn the most l i k e l y thermol- y s i s r e a c t i o n pathways. Second, based on the foregoing, model compounds mimicking the e s s e n t i a l r e a c t i v e m o i t i e s i n the l i g n i n subs t ra te were se lec ted and pyro lysed. Th i rd , and f i n a l l y , r e a c t i o n pathways sugqested by the model compound s t u d i e s were coupled w i t h a s t r u c t u r a l a n a l y s i s o f l i c n i n t o formulate a mathematical nodel which s imulated the e s s e n t i a l f ea tu res r?f ' l i g n i n thermolys is . TI-? r?r?se:it paper w i l l focus on the mode l l i ng o f l i g n i n thermolys is ; a specia l e f F o r t i s w d a t o compare our model r e s u l t s w i t h experimental data from 1 i g n i n t k w i n l y s t ? ? p m v i o u s l y repo r ted i n the l i t e r a t u r e .

I n o u t l i n e o f what fo l l ows , ou r approach t o t h e problem i s descr ibed f i r s t . Th is i nc ludes an a n a l y s i s o f l i g n i n s t r u c t u r e ; t h e choice o f model compounds w i t h a summary o f t h e i r exper imen ta l l y -asce r ta ined p y r o l y s i s pathways; and the l o g i c and mathematics o f t h e l i g n i n the rmo lys i s s imu la t i on . Representat ive r e s u l t s a re presented next, the s imulated l i g n i n thermolyses being descr ibed by the t ime- e v o l u t i o n o f products , i n c l u d i n g gases, aqueous l i q u i d s , phenol ic t a r s , and res idue (cha r ) . compared w i t h going product f r a c t i o n s .

Since l i g n i n i s a major component

We conclude w i t h a d i scuss ion wherein t h e r e s u l t s o f our s i m u l a t i o n are experimental data repo r ted i n the l i t e r a t u r e f o r each o f t h e f o r e -

L i g n i n S t r u c t u r e

L i g n i n i s a n a t u r a l pheno l i c polymer formed by an enzyme- in i t i a ted random f r e e - r a d i c a l co-polymer izat ion o f c o n i f e r y l , s i napy l and coumaryl a l coho l monomers. The a v a i l a b l e i n f o r m a t i o n concern ing l i g n i n s t r u c t u r e i s best summarized i n Freudenberg's (1) c l a s s i c d e p i c t i o n o f "a r e p r e s e n t a t i v e p o r t i o n o f spruce l i o n i n " , shown i n F igu re 1, which was the s t a r t i n g p o i n t f o r t h e present i n v e s t i o a t i o n . formula should n o t be i n t e r p r e t e d as a l i t e r a l chemical s t r u c t u r e f o r l i q n i n b u t r a t h e r as a schematic d e p i c t i o n o f t h e bond types and p ropor t i ons found t h e r e i n by experiments (1. 2, A) . Analys is o f Freudenberg's formula l e d t o i t s c h a r a c t e r i z a t i o n a lonq the f o l l o w i n g l i n e s . Each aromatic u n i t , a r i s i n g from a monomer, possesses i n general a s e t o f propanoid (3-carbon-atom) and methoxy-phenol subs t i t uen ts . These aromat ic u n i t s a r e connected by e i g h t types o f i n t e r u n i t l i nkages . t he B - e t h e r i f i e d guaiacy l g l y c e r o l moiety , as occurs between the methoxyphenol of

*Present Address: Department o f Chemical Engineer inq

+This work was supported by seed funds from the M I T Energy Laboratory .

Freudenberg's

The most p r e v a l e n t l i n k a g e i s

U n i v e r s i t y o f Delaware, Newark, DEL 19711

77

u n i t 6 i n F igure 1. Other l i nkages found, i n descending frequency o f occurrence, are a-ether ( u n i t s 3-4), diphenylmethane ( u n i t s 2-3), d iphenylether ( u n i t s 6-7) , biphenyl ( u n i t s 9-10), p i n o r e s i n o l ( u n i t s 8-9), and phenylcoumaran ( u n i t s 17-18). An essen t ia l feature o f l i g n i n s t r u c t u r e i s t h a t t he propanoid and methoxy henol subs t i t uen ts on a g i ven aromatic u n i t a r e e s s e n t i a l l y independent of one anotRer s ince they are never i nvo l ved i n bonding w i th each o t h e r . Thus, t h e p r o b a b i l i t y t h a t an aromatic u n i t should con ta in a propanoid s u b s t i t u e n t o f t ype k and a methoxyphenol o f type ,j i s t he product o f t he i n d i v i d u a l p r o b a b i l i t i e s o f t he occurrence o f k and j, as given i n F igure 1.

The fo rego ing p r o b a b i l i s t i c i n t e r p r e t a t i o n o f Freudenberg's l i g n i n formula i s reduced t o an aromatic u n i t m a t r i x A i n F igure 2. number o f aromatic u n i t s which possess t ype j methoxyphenol and t ype k propanoid subs t i t uen ts . l i g n i n ; these can o r i g i n a t e f rom each o f t h e t h r e e l i g n i n monomers and w i t h i n these t h e pheno l i c moiely may e i t h e r be f r e e o r e t h e r i f i e d i n any o f f o u r forms, namely phenethyl phenyl e the r , benzyl phenyl e the r , phenyl e t h e r and phenyl coumaran. Each column o f the m a t r i x represents a 3-carbon-atom propanoid s ide chain, r e s p e c t i v e l y gua iacy l g l y c e r o l (B-ether, a@-ether, a-phenyl & e t h e r ) , phenyl hydroxy acetone, cinnamaldehyde, p i n o r e s i n o l , conidendr ino id lactone, and phenylcoumaran.

The m a t r i x A o f F igu re 2 serves th ree purposes. t a i n e d i n i t s rows and columns a r e the bas i s f o r s e l e c t i o n o f model compounds r e l e v a n t t o l i g n i n the rmo lys i s . a concise p r o b a b i l i s t i c d e s c r i p t i o n o f t he l i g n i n subs t ra te . t h a t t h e present A-matr ix r e f e r s t o the p r o t o t y p i c a l spruce l i g n i n descr ibed by Freudenberg's formula; i n t h e more general case, & w i l l be a f u n c t i o n o f l i g n i n o r i g i n . ) Th i rd , as we s h a l l s h o r t l y f i n d , l i g n i n thermolys is g e n e r a l l y leaves aromat ic u n i t s i n t a c t w h i l e a l t e r i n g the s u b s t i t u e n t s ; a n a t u r a l extens ion o f t he A-matr ix t o account f o r a l l p o s s i b l e products from the rmo lys i s o f t h e mo ie t i es i n i t s rows and columns can then be used t o unambiguously c h r o n i c l e l i g n i n thermolys is i n terms o f t h e s u b s t i t u e n t s associated a t any t ime w i t h each o f t h e o r i g i n a l (conserved) aromat ic u n i t s o f t he l i g n i n subs t ra te .

Each m a t r i x element a j k represents the

Each row of t h e m a t r i x represents a s p e c i f i c methoxyphenol found i n

F i r s t , t he chemical mo ie t i es con-

(Note, i n c i d e n t a l l y , Second, t h e numerical values o f each element o f f e r

Model Pathways

Wodel compounds s e l e c t e d t o mimic the thermal reac t i ons o f l i g n i n a re l i s t e d i n Table 1. For each e n t r y , t h e t a b l e l i s t s an abbrev iated name, chemical s t r u c t u r e , t h e aspect o f l i g n i n s t r u c t u r e modelled, and experimental p y r o l y s i s cond i t i ons of temperature, h o l d i n g t i m e , and i n i t i a l concen t ra t i on . I t can be v e r i f i e d t h a t the e n t r i e s i n Table 1 model most o f t h e i n t e r u n i t l i nkages ( I L ) , methoxyphenol s u b s t i t u e n t s (MP), and propanoid chains (PC) which appear i n F igure 1. PPE models t h e B-ether l i n k a g e most p reva len t i n l i g n i n ; guaiacol models the methoxyphenol s u b s t i t u e n t assoc iated w i t h c o n i f e r y l a l coho l which i s t h e dominant monomer i n spruce l i g n i n ; v e r a t r o l e models an e t h e r i f i e d methoxyphenol; cinnamyl a l coho l models a propanoid cha in s u b s t i t u e n t , as do cinnamaldehyde, iso-euqenol, and acetophenone. mo ie t i es which, w h i l e n o t o r i g i n a l l y present i n l i g n i n , a r i s e d u r i n g i t s thermolys is ; f o r example, s a l i g e n o l models a propanoid enol mo ie ty r e s u l t i n q from t h e pr imary r e v e r s i o n o f a g u a i a c y l - g l y c e r o l @-ether . S t i l l o the r compounds i n Table 1, such as an iso le , served as c o n t r o l s i n the mechanis t ic i n t e r p r e t a t i o n o f t he model pyro lyses.

Resul ts o f t h e model compound pyro lyses a r e summarized i n Table 2. s t r a t e , the t a b l e d e l i n e a t e s t h e observed p y r o l y s i s pathways, t h e i r assoc iated products , and r e a c t i o n k i n e t i c s . secondary pathways, i n v o l v i n g reac t i ons o f a pr imary product , a r e des i nated w i t h an

E*(kcal /mol ) ) f o r p s e u d o - f i r s t order r e a c t i o n ; a c t u a l r e a c t i o n orgers, where exper imen ta l l y asce r ta ined , arequoted i n t h e f i n a l column o f t h e t a b l e . example, i n e n t r y 1, PPE decomposes by p r imary r e a c t i o n R1 t o phenol and s tyrene

S p e c i f i c a l l y ,

Note a l s o t h a t some o f t he compounds i n Table 1 were chosen t o model

For each sub-

Primary pathways are des ignated w i t h an R w h i l e

S. React ion k i n e t i c s a r e descr ibed by Arrhenius parameters ( l o g l A ( s - 9 ), As an

78

products; the associated Arrhenius parameters a re (11.1, 45.0) and the reaction was experimentally found to be f i r s t order in PPE; fur ther , the styrene product of R 1 undergoes secondary reaction S1 t o form ethyl benzene, toluene, and benzene. The data Presented in Table 2 now permit a quant i ta t ive description of reaction pathways and kinetics in lignin thermolysis.

Simulation of Lignin Thermolysis

The logic employed in our simulation of lignin thermolysis i s depicted in Figure 3. Consider f i r s t some typical transformations experienced by a lignoid aromatic uni t as shown in Figure 3a. element a During thermolysis, suppose the propanoid chain of !’is sequentially subjected t o &ether reversion, pathway R 1 : P P E i n Table 2 , and enol product dehydration, by pathway R1:SAL in Table 2 . the substrate I wi l l , in p a r t , be transformed to the intermediate product 11 with concurrent evolution of water. However, 11 can fur ther react by parallel pathways R1 :CAD and R1 :GLIA, respectively leading t o propanoid chain decarbonylation and methoxyphenol demethanation; t h u s a t some fur ther time t p . I1 w i l l , in p a r t , be transformed t o 111, with concurrent evolution of carbon monoxide and methane. should be noted that in Figure 3a, the original aromatic ring remains in tac t while i t s propanoid chain and methoxyphenol substituents are variously a1 tered, chronic1 ing the course of thermolysis. In mathematical terms, each s u k t i t u e n t contained in the original A matrix gives r i s e t o a new s e t of substituents t h a t represent i t s thermolysis according t o the pathways given in Table 2 . (aromatic un i t s ) of the original element a j k of A are conserved while beinq redistributed into the elements Pmn of a new (product)-matrix which represents a l l possible subst i tuents tha t can a r i s e from the original s e t . will show t h a t A i s rea l ly a submatrix (the t o p l e f t corner, say) of E. fur ther detai l into the nature of the !-matrix, and the methods for product accounting, i s given in Figure 3b. Consider the coniferaldehyde uni t I 1 in l ignin, undergoing thermolysis. I n Figure 3a, for s implici ty , t h i s was shown t o react by two parallel pathways; however, in pract ice , i t will undergo a l l possible reactions accessible t o i t s methoxyphenol a n d propanoid chain subst i tuents . Since these subst i tuents are independent, the products will be formed by a superposition of the type shown in Figure 3b. The methoxyphenol in I1 i s modelled by quaiacol A , which can pyrolyse b,v pathways R 1 : GUA and R2: GUA of Table 2 t o catechol B and phenol C . chain in I 1 i s modelled by cinnamaldehyde D which can pyrolyse by R 1 : CAD t o styrene E . Thermolysis of I 1 will then form a l l of the products shown in Fiqure 3b (and the i r associated gases) , in amounts commensurate with the lkinetics of the pathways involved.

The foregoing chemical logic was employed to mathematically simulate a constant volume batch pyrolysis of l ignin. equations, which described the time-variation o f aromatic u n i t subst i tuents , were solved numerically from a n i n i t i a l condition representing Freudenberg’s spruce lignin. t o a l l other subst i tuents , so t h a t :

I n i t i a l l y (time t =O), t h i s unit I will be recognized as of the spruce lignin matrix A.

A t some time t , then ,

I t

A t any time, the contents

A l i t t l e ref lect ion Some

The propanoid

In t h i s simulation, a s e t of d i f fe ren t ia l

The r a t e of change of a given substituent was, in general, proportional

Differential Equations: dX/dt = EX; dY/dt = LY (1 1 ( 2 ) I n i t i a l Condition:

In these the vector X represents a l l methoxyphenol-related substituents while vector Y represents propanoid chain-related substituents: these a r e , respectively, the rows and columns of the product matrix P . part from Table 2 , respectively c o n t a i n t h e kinetic ra tecons tan ts o f those chemical reactions producing the components of vectors X and Y . coincide with the sums of each row and column in the matrix 5, depictinq the lignin substrate , Values of the vectors X and Y a t any subsequent time t are a consequence of a l l possible chemical transformations embodied in the matrices K and L . The contents of a n element pmn of the product matrix P then show the number Gf aromatic

X = Xo, Y = Y o a t t = 0

The matrices K and L , derived in large

The i n i t i a l values X o , Y o

79

u n i t s w i t h methoxy-phenol r e l a t e d s u b s t i t u e n t m and propanoid cha in - re la ted sub- s t i t u e n t n. o f product pmo as e i t h e r t a r ( s i n g l e - r i n g aromatic u n i t ) o r res idue ( m u l t i p l e aromat ic r i n g s ) . a v a i l a b l e (4). Resul ts

Thermolysis o f t h e p r o t o t y p i c a l spruce l i g n i n of F igure 1 was s imu la t d a t temperatures

r e s p e c t i v e l y . me t i c p l o t o f p roduc t y i e l d , expressed as weight pe rcen t o f o r i g i n a l l i g n i n subst rate, versus t ime. Four p roduc t f r a c t i o n s , namely, gas, aqueous l i q u i d s , phenol ic l i q u i d s and carbonaceous res idue, w i l l be considered.

I n regard t o gas e v o l u t i o n , t h e s i m u l a t i o n accounts f o r methane and carbnn monoxide. I n the uppermost s e c t i o n o f F i g u r e 4 i t can be seen t h a t bo th gases evolve f a s t i n i t i a l l y and then more s lowly , a t t a i n i n g asymptot ic y i e l d s o f c i r c a 6 wt %, w i t h methane s l i g h t l y exceeding CO. The methane a r i s e s p r i m a r i l y f r o m quaiacy types o f methoxyphenol mo ie t i es , both those which are i n i t i a l l y present w i t h a f r e e hydroxy l and those which a r i s e by r e v e r s i o n o f e t h e r i f i e d hyd roxy l s . The C O o r i g i n a t e s b o t h from t h e decarbonylat ion o f ca rbony l - con ta in ing propanoid chains and, t o a l e s s e r ex ten t , from t h e demethoxy lat ion o f methoxyphenols. An account o f these dual s i t e s f o r CO re lease possessing q u i t e d i f f e r e n t a c t i v a t i o n energ ies r e l a t i v e t o the s i t e s fo r CH4 release, the s i m u l a t i o n p r e d i c t s t h a t t he r a t i o o f CO/CHq should be >1 a t low temperatures and conversions, <1 a t moderate temperatures and conversions (as i n F igu re 4) , and then again >1 a t h i g h temperatures.

Among aqueous l i q u i d s , t he s i m u l a t i o n accounts f o r water and methanol. As seen i n the second ( f rom top ) s e c t i o n of F igure 4, t he water y i e l d increases monotonica l ly , bu t w i th decreasing s lope, t o an u l t i m a t e va lue o f %5 w t 5:. The water a r i s e s f rom two sources; predominant ly i t i s formed from dehydrat ion o f enol u n i t s which r e s u l t a f t e r 8-ether reve rs ion ; minor amounts a l so a r i s e from degradat ion o f cinnamyl- a l coho l types o f propanoid chains. about 0.1 w t %. This r a t h e r smal l va lue comes about because, i n t h e s imu la t i on , methanol a r i ses s o l e l y from cinnamyl a lcohol mo ie t i es , which a re r e l a t i v e l y r a r e i n l i g n i n ; f u r t h e r , the methanol-forming pathway i s i t s e l f r e l a t i v e l y minor amongst cinnamylalcohol p y r o l y s i s pathways.

The phenol ic l i q u i d s f r a c t i o n o f our s imulated l i g n i n the rmo lys i s inc luded some f i f t y i n d i v i d u a l pheno l i c compounds. The fo rma t ion versus t i m e f o r two se ts o f pheno l i c products i s shown i n the two lowest sec t i ons o f F igu re 4. I n the upper o f these two sec t i ons , i t can be seen t h a t the gua iaco l p roduc t i on increases i n i t i a l l y , reaches a maximum, and then decreases towards zero a t l o n g t imes; t he catechol product ion increases s l o w l y a t low t imes but more s t r o n g l y a t l onger times; phenol product ion increases mono ton ica l l y w i t h i nc reas ing t ime but always remains l e s s than ca techo l . Q u a l i t a t i v e l y the same behavior i s e x h i b i t e d i n t h e lowest sec t i on o f F igure 4 by methy lgua ico l , methy lcatechol , and para-cresol products , each o f which i s the me thy l - subs t i t u ted analogue o f the preceding products ; note however t h a t y i e l d s o f t h e m e t h y l - s u b s t i t u t e d phenols are almost an o rde r o f magnitude h ighe r than those of t h e i r u n s u b s t i t u t e d homologues. F igure 4 a r i s e from t h e f o l l o w i n g considerat ions. d i r e c t l y i n l i g n i n , and f u r t h e r a r i s e s from r e v e r s i o n o f e t h e r i f i e d methoxy-phenols; assoc iated w i t h these guaiacy l u n i t s a re var ious propanoid chains, a l s o s u b j e c t t o degradation. Primary guaiacol products , degrading t o v i n y l guaiacol , and hence t o e t h y l - , methy l - , and unsubs t i t u ted gua ico l . Fu r the r , each g u a i c y l mo ie ty i s capable o f demethanation and demethoxylat ion, which r e s p e c t i v e l y y i e l d the corresponding catechol and phenol. Each guaiacol p roduc t thus possesses pathways f o r f o rma t ion and des t ruc t i on , r e s u l t i n g i n the c h a r a c t e r i s t i c y i e l d maxima seen i n F iqu re 4. From t h e foregoing, ca techo ls

The na tu re o f s u b s t i t u e n t s m and n f u r t h e r pe rm i t s t h e c l a s s i f i c a t i o n

D e t a i l s o f t h e s i m u l a t i o n l o g i c , mathematics, and numer ica l eva lua t i on a r e

o f 300, 400, 500, and 6 0 0 C t o ho ld ing times of l o4 , lo4, l o 2 , and 10 7 seconds, Representat ive r e s u l t s a t 5 0 0 C a re presented i n F iaure 4, an a r i t h -

The u l t i m a t e methanol y i e l d p red ic ted i s o n l y

Phenol ic p roduc t t rends seen i n The gua iacy l moiety occurs

Thus coni fera ldehyde and guaiacy l v i n y l ketone a re t h e most n e a r l y

80

are seen t o be secondary products, a r i s i n g from guaiacy l moiety demethanation; t h i s causes t h e i r i n i t i a l p roduc t i on t o be slow b u t a t l ong t imes they become the dominant phenol ic products . demethoxylat ion, noted above, and coumaryl a l coho l monomer u n i t s d i r e c t l y i nco rpo ra ted i n the l i g n i n ; t h e former source being o f q rea te r impor t . Phenol s u b s t i t u t i o n pa t te rns p a r a l l e l those o f guaiacol , w i t h a l k y l s ide-chains ranging from coumar- aldehyde t o v i n y l - , e t h y l - , and unsubs t i t u ted phenol. Y ie lds o f phenols r e l a t i v e t o catechols increase somewhat w i t h i nc reas ing temperature, s ince guaiacy l demethoxylat ion i s more h i g h l y a c t i v a t e d than pua iacy l demethanation: liowever t h e absolute y i e l d s o f phenols always remained lower than those o f ca techo ls .

F i n a l l y , phenols a r i s e from two major sources, namely qua iacy l

According t o our s imulat ion, t he carbonaceous res idue i s comprised o f a l l aromat ic u n i t s i nvo l ved i n i n t e r u n i t bonding. I f the gas, aqueous l i q u i d , and pheno l i c product f r a c t i o n s a re designated as v o l a t i l e , and a l l m u l t i p l e r i n g aromat ics as non v o l a t i l e , then the s imulated carbonaceous res idue f r a c t i o n can be r e l a t e d t o the weight l o s s t h a t would be observed du r ing l i g n i n thermolys is . weight - loss versus t ime curves a re shown by t h e dashed l i n e s i n F igu re 5, which w i l l be more f u l l y discussed i n the next sec t i on .

Such s imulated

Discuss ion

The d i scuss ion w i l l be con f ined t o comparisons between the present r e s u l t s and prev ious l i t e r a t u r e , as embodied i n the m a t r i x o f Table 3. In t he r a m o f t h i s ma- t r i x , t he f o u r major product f r a c t i o n s have been de l i nea ted i n terms o f o v e r a l l and c o n s t i t u e n t component y i e l d s . The m a t r i x has s i x columns, rep resen t ing ou r model p r e d i c t i o n s and f i v e sets o f l i t e r a t u r e references. The l a t t e r i nc ludes t h e c o l l e c t e d r e p o r t s o f several authors as summarized i n re ference 4, t h e data o f I a t r i d i s and Gavalas ( 5 ) , o f Kirshbaum @),and o f Domburg (7, g. In each m a t r i x element, a numerical va lue o r comment i n d i c a t e s t h a t i n f o r m a t i o n r e l e v a n t t o t h a t row was repor ted, whereas an ' X ' i m p l i e s t h a t i t was n o t . The p resen t s i m u l a t i o n column 1, prov ides e n t r i e s f o r each r o w save CO2 y i e l d . The o v e r a l l gas f r a c t i o n i s the sum o f CO and CHg; these a re by f a r t he p reva len t c o n s t i t u e n t s o f t h e l i g n i n o f f -gas . The aqueous d i s t i l l a t e was composed o f water and methanol on l y ; acetone, a c e t i c a c i d and o t h e r minor l i q u i d products were n o t i nc luded i n the s i m u l a t i o n . The phenol ic f r a c t i o n ccmprised the sum o f a l l s i n g l e r i n g phenols; t h i s o v e r a l l y i e l d should correspond bes t t o the o v e r a l l t a r y i e l d repo r ted i n p y r o l y s i s experiments. F i n a l l y , t h e carbonaceous res idue f r a c t i o n i s composed o f a l l m u l t i p l e r i n g aromatic u n i t s . The i n v e s t i g a t i o n s o f c o l l e c t e d authors (T), column 2, p rov ide d e t a i l e d accounts o f gas and aqueous d i s t i l l a t e y i e l d s , and o v e r a l l t a r and char y i e l d s . i n v e s t i g a t i o n s , e n t r i e s i n t h i s column a re b e s t considered the asymptot ic ' u l t i m a t e ' y i e l d s o f d e s t r u c t i v e d i s t i l l a t i o n s . obta ined i n a r e a c t o r designed t o emphasize pr imary reac t i ons , p r o v i d i n g d e t a i l e d temperature-t ime in fo rma t ion and e n t r i e s f o r a l l save water and o v e r a l l aqueous d i s t i l l a t e y i e l d s . Kirshbaum 6 prov ided o v e r a l l gas, phenol ics , and carbonaceous

d e s c r i p t i o n of phenol ic product spect ra and DTA/DTG weight l o s s data were g i ven by DomburgQ, 8J. The d iscuss ion t o f o l l o w considers each row o f Table 3; note t h a t a l l y i e l d s a re i n weight percent o f o r i g i n a l l i g n i n subs t ra te .

The simulated o v e r a l l gas f r a c t i o n rose w i t h i nc reas ing t ime and temperature and u l t i m a t e l y achieved a va lue o f about 15% a t 600 C. Th i s compares favo rab ly w i t h the data of c o l l e c t e d authors ( 4 ) i n Table 3, where gas y i e l d s ranged from about 10-20%. t h i s inc luded 7.2% Cop. As discussed below, t h i s r a t h e r h igh CO2 con ten t may be due t o t h e i r use o f a K r a f t l i g n i n . i n good agreement both w i t h the s imu la t i on and e a r l i e r l i t e r a t u r e . A d d i t i o n a l l y , Kirshbaum r e p o r t s t o t a l gas (and losses) y i e l d o f ~ 5 % a t 250 C and %18% a t 600 C . The s imulated (CH4, CO) y i e l d s a r e r e s p e c t i v e l y (6.0, 5.0) % a t (500 C , 100s) and

Because d e t a i l e d temperature-t ime i n f o r m a t i o n i s l a c k i n g f o r many of these

The data o f I a t r i d i s and Gavalas (?)were

res idue y i e l d s ; d e t a i l e d pheno v. i c product spect ra were prov ided a lso. D e t a i l e d

I a t r i d i s and Gavalas r e p o r t an o v e r a l l y i e l d as h igh as 23% a t 650 C , b u t

Omi t t i ng C02, t h e i r o v e r a l l gas y i e l d i s 16%,

81

(6.1, 9.0) % a t (600 C, 7 s ) ; b o t h these CH4 and CO yields are in substantial agreement with the col lected l i t e ra ture (5) which provides ultimate ( C H 4 , C O ) y ie lds of (7 .0 , 7.0) I. reference 5 , b u t , in terest ingly, these authors report t h a t the experimental CO/CH4 r a t i o variFd from about 2 . 3 a t 400 C t o 0.89 a t 500 C a n d 1.8 a t 600 C , which closely accords with the behavior of t h i s ra t io in our simulation. This was e a r l i e r in te r - preted in terms of dual s i t e s f o r CO release from l ignin.

The simulated overall yield of aqueous l iquids , based on the sum of water and methanol yields , was about 6%, appreciably lower than the average yields of %15% reported by the collected authors (4). Of the two individual components, the simulated water yields of 6% a r e about half of the values reported in the l i t e r a t u r e , although these l a t t e r a re often unreliable on account of water being physically associated with the lignin o r introduced during i t s isolat ion. Simulated methanol yields of 0.1% a r e a l so substant ia l ly lower than the yields of 0.28 t o 1.5% reported by the collected authors ( 4 ) . I t \40Uld appear that fur ther pathways for both water a n d methanol production need t o be ident i f ied and incorporated in to the present model of lignin thermolysis.

The simulated overall yield of phenolic liquids ranged from 7 t o 80%. phenolic fraction yields typical ly range from 3 t o 30% ( 4 ) , although t a r yields greater t h a n 50% h a v e been reported (9 ) . exceed experimental f o r two l ikely reasons. F i r s t , many complex phenols in the tar fract ion are not experimentally identified and second, o u r simulation did not con- s ider the condensation and polymerization reactions which might lower the yield of single ring phenols i n practice. I n regard to individual phenols, the present simulation predicts most of the t h i r t y phenols which have been detected in the l i t e r a t u r e (6, 7, E). agree with experimental values t o w i t h a half a n order of magnitude. l a r ly noteworthy t h a t deviations between the present simulation a n d experiments a r e no greater than deviations between individual experiments.

The simulated carbonaceous residue yields of 91% a t 300 C and 104s and 40% a t 600 C and 7s compare favorably with the l i t e r a t u r e . In Table 3 , ultimate tar yields from destructive d i s t i l l a t i o n (5) were 40 t o 60%. I a t r i d i s and Gavalas (5) report weight losses of 20% and 53% a t 400 and 600 C , respectively, corresponding t o char yields of 80% a n d 47%. Kirshbaum (6) reports a char yield of 91% a t 250 Cand only 26% a t 600 C. provides simulated carbonaceous residue yields tha t are i n good accord with the experimental l i t e r a t u r e .

Finally, simulated weight-loss kinetics, derived from the carbonaceous residue yields as n o t e d e a r l i e r , are compared with the experimental data reported by Ia t r id i s and Gavalas (5) i n Figure 5. (dashed), accord well with the experimental weight loss curves ( s o l i d ) , b o t h in regard t o shape and absolute magnitudes. t h a t the simulation was based en t i re ly on our a pr ior i description of lignin s t ruc- tu re , reaction pathways, and kinet ics , and incorporated no information derived from actual lignin thermolyses. Furthermore, the modest deviations between simulated and experimental weight loss curves in Figure 5 can reasonably be at t r ibuted t o differences between t h e respective lignin substrates. Douglas for precipi ta ted Kraft 1 ignin, whereas the present simulation was based on Freudenberg's unperturbed "protolignin." Kraft pulping a l t e r s the chemical nature of l ign in , resul t ing in increased internal condensations, with the original reactive a- and B-ether linkages transformed into less reactive diphenyl-methane, ethane, a n d ethylene linkages; i t a lso introduces carboxylic acid units into the lignin macro- molecule. The low temperature react ivi ty of a Kraft lignin might be expected t o be greater t h a n i t s protolignin counterpart because of f a c i l e C02 evolution from the carboxylic acid uni t s . A t higher temperatures and conversions, the react ivi ty of a Kraft l ignin may well be lower than t h a t of the protolignin since relat ively re-

Simulated methane and CO yields both somewhat exceed those of

Experimental

The simulated Fhenolic f ract ion yields

I n most cases , the simulated yields o f individual phenols I t i s particu-

The present def in i t ion of residue a s multiple ring aromatics evidently

I t can be seen t h a t the simulated weight loss curves

The observed agreement i s noteworthy i n

The au thor s (5) used a

82

f r a c t o r y diphenylmethane, ethane and e thy lene u n i t s have rep laced t h e o r i g i n a l r e a c t i v e a - a n d B-ethers. I a t r i d i s and Gavalas r e p o r t CO2 y i e l d s o f 5.9% a t 400 C and 1205, and 4.1% a t 600 C and 10s. These suggest a cons tan t number o f e a s i l y decarboxy lated a c i d s i t e s i n t h e i r subs t ra te . Fur ther , t h e au tho rs ' repo r ted weight l o s s o f 20% a t 400 C and 120s exceeds our s imulated we igh t loss o f 13% by an amount s u b s t a n t i a l l y equal t o t h e i r CO2 y i e l d . A t 600 C and 10s t h e exper imenta l weight l o s s co r rec ted f o r CO2 i s ~ 5 0 % , somewhat lower than ou r s imulated va lue o f 60% on account o f t h e reduced r e a c t i v i t y o f t h e i r K r a f t 1 i g n i n .

Summary and Conclusions

Mathematical s i m u l a t i o n o f w h o l e - l i g n i n pyro lyses, a t 300 t o 600 C w i t h h o l d i n g t imes of 1 t o 104S, was achieved by combining a s t a t i s t i c a l i n t e r p r e t a t i o n o f l i g n i n s t r u c - t u r e w i th exper imenta l r e s u l t s o f model compound pyro lyses. s imulat ions, expressed i n terms o f product f r a c t i o n s as a percent o f i n i t i a l l i g n i n was :

( i ) Gas F rac t i on : p rev ious experimental l i g n i n pyro lyses; respec t i ve u, l t imate y i e l d s t y p i c a l l y 15%, 6%, and 9% were i n q u a n t i t a t i v e agreement w i t h t h e l i t e r a t u r e . of (CH4/CO) r a t i o w i t h t ime and temperature f u r t h e r agreed w i t h t h a t r e c e n t l y repor ted by I a t r i d i s and Gavalas (5). (ii) Aqueous F rac t i on : experimental y i e l d s o f 12%. magnitude lower than t h e l i t e r a t u r e y i e l d s o f 0.3-1.5%.

( i i i ) Phenol ic F rac t i on : h ighe r than exper imen ta l l y observed. i n d i v i d u a l phenols repo r ted i n t h e l i t e r a t u r e . Simulated y i e l d s o f s imple i n d i v i d u a l guaiacols , cathechols, sy r i ngo ls , and phenols, each nominal ly 2%, were w i t h i n the band o f values repo r ted i n t h e l i t e r a t u r e .

( i v ) Carbonaceous Residue: and 600 C were n e a r l y c o i n c i d e n t w i t h t h e experimental curves repo r ted by I a t r i d i s and Gavalas (5) f o r p y r o l y s i s o f a K r a f t l i g n i n . between these curves, a t bo th low and h igh temperatures, were t raced t o s t r u c t u r a l d i f f e r e n c e s between t h e r e s p e c t i v e l i g n i n subs t ra tes .

References

I n t h e l i g h t o f these asse r t i ons , i t i s i n t e r e s t i n g t h a t

The outcome o f these

Simulated o v e r a l l gas, methane, and CO y i e l d s accorded w i t h

The s imulated v a r i a t i o n

Simulated water y i e l d s were t y p i c a l l y about h a l f t h e r e p o r t e d Simulated methanol y i e l d s were h a l f an o rde r o f

Simulated o v e r a l l pheno l i c l i q u i d s y i e l d s were g e n e r a l l y The s i m u l a t i o n accounted f o r more than t h i r t y

Simulated curves o f weight l o s s versus t ime a t 400, 500,

Also, t h e modest disagreements

1. Freudenberg, K . , Neish, A.C., @ g t i _ _ t u t i o n _ n d B-iosynthesis o f Lign_i_n, Springer-Verlag, New York (1968).

2 . Ha rk in , J.M., i n Ba t te rsby and Tay lo r , Ox ida t i ve Coupl ing o f Phenols, Marcel-Dekker (1967).

3. Sarkanen, K . V . , i n Sarkanen, K.V., and Ludwig, C.H., eds., &ninsl>c_cu_r Formation, S t r u c t u r e and Reactions, Wi ley In te rsc ience , New York, (1971) .

4. K le in , M.T., Model Pathways i n L i g n i n Thermolysis, Sc.D. Thesis, Departmf of Chemical Engineering, M.I.T., Cambridge, Mass. (1981).

5. I a t r i d i s , B . and Gavalas, G.R., I & EC Prod. Res. Dev., 18 ( 2 ) , 127 ( 6. Kirshbaum, I . Z . , Domburg, G . E . , Sergeeva, V.N., Khim. Dev. No. 4, 96 7. Dovburg, G.E., Sergeeva, V.N.,Kalnish, A.I., Thermal Analys is , Vol .3

(Proc. 3 rd ICTA Davos (1971)) pp. 327-40, Burkhaeuser, Basel, (1972). 8. Domburg, G.E. , Sergeeva, V.N. , J. Thermal. Anal., 1, 53 (1969). 9. Domburg, G.E. , Kirshbaum, I . , Sergeeva, V.N., Khim; Dev. 7, 51 (1971)

979). 1976)

83

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e

e

0

9

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0

.-.

X

rr

$ B

E %

2 8 0 c, -a " 0 L Ln" - 0

2("

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c ". W' c ..- ..

%

Y

85

FIGURE 1. MODEL OF SPRUCE LIGNIN STRUCTURE (F reudenberg , 1 ) -

FIGURE 2. AROMATIC UNIT MATRIX A FOR SPRUCE LIGNIN

86

FIGURE 3 . LOGIC OF LIGNIN THERMOLYSIS SIMULATION.

( a ) ( b ) Superpos i t ion o f Nodel Pathways.

Thermal Transformation o f Lignin Moiety.

R1 :CAD ___3

R1 : GUA> R1 : PPE, R1*1,>

OH I ( t=O) I1 ( t = t , ) I11 ( t = t 2 )

Moiety i n L ignin

I 0, I

I ‘ A . D bOMe 0 B a o q :$ I I I I Products

o f OH OH

I I I ‘ A . E 0 bOHc B . E C . E

I I I

9

Model 6 Compounds A

Guaiacol Cinnamaldehyde

87

ENHANCED COAL LIQUEFACTION WITH HIGH BOILING SOLVENTS. 0. D. Whitehurst. Mobil Research & Development Corp., P.O. Box 1025, Princeton N- In the accelerated development of coal l iquefaction since 1973, i t has been the gen-

eral practice t o use d i s t i l l a t e s as recycle solvents. This stems from the e a r l i e r German experience where recycling asphaltenic products required more severe processing. Recent- l y , i t has been demonstrated tha t the inclusion of vacuum tower bottoms o r of solvent fractionated heavy products i n a recycle loop can produce dramatic process improvements.

been conducted us ing both model compounds, process derived materials, and f r ac t ions thereof. These s tudies ident i f ied polycondensed aromatics as e f fec t ive solvent components. Due t o t h e i r r e l a t ive ease of hydrogenation and dehydrogenation they can e f fec t ive ly in t e rac t w i t h hydroaromatic species i n the coal (H-shuttl ing), with l e s s ac t ive H donors o r w i t h hydrogen gas (H-transfer). an important r o l e in these reactions.

produce adverse reactants. generation of optimal recycle solvent composition.

pound studies and the behavior of d i f fe ren t chemical c lasses i n heavy process solvents can lead t o improvements in coal l iquefaction processes.

An investigation of the mechanisms of coal conversion i n h i g h boil ing solvents has

Mineral matter ca t a lys i s can play

Polyfunctional components have a propensity fo r promoting char formation and can Information of t h i s type can lead t o ident i f ica t ion and

These s tudies show t h a t the mechanistic pathways discernible from the model com-

89

H-COAL SLUQRY O I L COMPOSITIQN AND PROCESS PERFORMANCE

F. P. Burke and X. A . Winschel

ConOco Coal Development Company, Research D i v i s i o n , L i b r a r y , PA 15129

INTRODUCTION

The H-Coal p r o c e s s , developed by Hydrocarbon Research , I n c . , i s a c a t a l y t i c c o a l hydrogenat ion i n which t h e c o a l i s contac ted w i t h , u s u a l l y , an alumina suppor ted Co/MO, o r similar c a t a l y s t i n an upflowing f l u i d i z e d bed. p r o c e s s a r e t h e r e a c t o r i n t e r n a l s , which a l l o w f o r f l u i d i z a t i o n of t h e c a t a l y s t bed, and c a t a l y s t a d d i t i o n and withdrawal systems t o a l l o w maintenance of t h e c a t a l y s t a c - t i v i t y . The 3 TPD p r o c e s s development u n i t (PDU), opera ted by H R I a t Trenton , N J , has been used to s t u d y f e e d c o a l and s p a c e v e l o c i t y e f f e c t s , and t o provide d e s i g n da ta f o r sca le -up of the p r o c e s s . A schemat ic of t h e u n i t ( F i g u r e 1) shows t h a t t h e c o a l is f e d t o t h e r e a c t o r as a s l u r r y w i t h two r e c y c l e components. c o n t a i n s d i s t i l l a t e , n o n - d i s t i l l a t e o i l s ( r e s i d ) , and s o l i d s . The c l e a n o i l t a n k (COT) i s a s u r g e v e s s e l c o n t a i n i n g atmospheric s t i l l bottoms and vacuum s t i l l overhead. amounts of t h e s e d i s t i l l a t e s i n t h e c l e a n o i l t a n k c a n b e independent ly v a r i e d .

The d i s t i n g u i s h i n g f e a t u r e s of t h e

The hydroclone over f low (HO)

The

An i n t e r e s t i n t h e composition of t h e s e r e c y c l e o i l s , and how t h e i r composition is r e l a t e d t o process performance, was t h e m o t i v a t i o n f o r a r e c e n t l y completed program t o a n a l y z e d a i l y samples o f r e c y c l e s l u r r y o i l s from H-Coal PDU Runs 5 , 8 and 9 by a v a r i e t y of a n a l y t i c a l t e c h n i q u e s , and t o r e l a t e t h e composition d a t a t o p r o c e s s p e r f o r - mance i n t h o s e PDlI r u n s . PDU Runs 5 and 8 were made w i t h I l l i n o i s 6 c o a l w h i l e PDU 9 used Kentucky 11 PDU Runs 5 and 9 were made i n t h e Syncrude mode (space v e l o c i t y = 31) whi le PDU Run 8 c o n s i s t e d of o p e r a t i o n s i n b o t h t h e Fuel O i l and I n t e r - media te modes (Table 1 ) . D a i l y samples of t h e c l e a n o i l t a n k and t h e hydroclone over- f low were taken by H R I and shipped t o CCDC f o r a n a l y s i s . The a n a l y t i c a l t echniques used and t h e i n f o r m a t i o n d e s i r e d from each are g iven i n T a b l e 2 . The o b j e c t of t h e s t u d y w a s t o de te rmine t h e r e l a t i o n s h i p between s l u r r y o i l composition and process p e r - formance i n e i g h t s p e c i f i c a r e a s :

1.

2.

3.

4 .

5.

6.

7.

8 .

Changes i n t h e s l u r r y r e c y c l e stream composition d u r i n g s t a r t u p .

The manner i n which t h e process reaches s t e a d y s t a t e o p e r a t i o n d u r i n g s t a r t u p .

The composition of t h e r e c y c l e s t ream d u r i n g s t a b l e o p e r a t i o n .

The changes i n r e c y c l e composition i n response t o planned v a r i a t i o n s i n pro- c e s s v a r i a b l e s .

Changes i n t h e r e c y c l e composition which cause OK r e s u l t from unplanned u p s e t s in t h e p r o c e s s o p e r a t i o n .

Changes i n t h e r e c y c l e composition as ev idence of changes i n c a t a l y s t a c t i v i t y .

D i f f e r e n c e s i n r e c y c l e composition as a f u n c t i o n of space v e l o c i t y (mode).

D i f f e r e n c e s i n r e c y c l e composition as a f u n c t i o n of feed c o a l (same space v e l o c i t y ) .

In making i n t e r p r e t a t i o n s of t h e s e d a t a i t is impor tan t t o recognize t h a t t h e r e are two ways i n which t h e d a t a can be expressed . The r e c y c l e s l u r r y o i l c h a r a c t e r i z a t i o n s can b e g iven as composi t ions , O K i n t e n s i v e v a r i a b l e s . For example, t h e weight p e r c e n t

90

O f benzene s o l u b l e s i n t h e r e c y c l e r e s i d r e p r e s e n t s t h e n a t u r e of t h e m a t e r i a l t h a t i s be ing r ecyc led , without r e f e r e n c e t o t h e amount. A l t e r n a t i v e l y , t h e d a t a can b e ex- p re s sed on a r e c y c l e r a t e , o r e x t e n s i v e v a r i a b l e b a s i s . Thus, t h e pounds of benzene i n s o l u b l e s r ecyc led p e r pound of c o a l fed r e f l e c t s bo th t h e composition of t h e r e c y c l e r e s i d , and t h e t o t a l r e c y c l e r a t e of t h a t r e s i d . Both t h e composi t ion and r e c y c l e r a t e d a t a can be used t o draw conc lus ions r ega rd ing s t e a d y s t a t e performance. In t h e work desc r ibed h e r e , a l l conc lus ions concerning s t e a d y s t a t e performance a r e based on a s t a - t i s t i c a l t r ea tmen t of t h e d a t a which compares v a r i a t i o n s i n t h e da ta w i t h t h e expe r i - mental u n c e r t a i n t y of t h e measured v a r i a b l e s . The mathematical b a s i s of t h i s t r ea tmen t is desc r ibed i n t h e f i r s t t o p i c a l r e p o r t p repa red under t h i s c ~ n t r a c t ( ~ ) . p re sen ted below a r e a b s t r a c t e d from t h e much more e x t e n s i v e body of d a t a inc luded i n t h e two t o p i c a l r e p o r t s and f i n a l r e p o r t p repa red under t h i s ont tract(^'^'^).

The r e s u l t s

The purpose of t h i s paper i s t o i l l u s t r a t e t h e major conc lus ions reached i n t h i s s t u d y .

COMPARISONS OF RECYCLE COMPOSISIONS

There fo re , confirming r e s u l t s of o t h e r a n a l y s e s a r e n o t g e n e r a l l y p r e s e n t e d .

Because H-Coal is a hydrogenat ion p r o c e s s , 'H-NMR was expected t o p rov ide a u s e f u l measure of r e c y c l e o i l composi t ion. PDU Runs 5 and 9 and f o r t h e two space v e l o c i t y pe r iods of PDU Run 8. Runs 5 and 9 used f o r ave rag ing were chosen t o r e p r e s e n t t h e b e s t approach t o s t eady s t a t e i n those runs. Because of a number of u p s e t s over t h e f i r s t 16 days, w e could no t i d e n t i f y s t eady s t a t e pe r iods f o r PDU Run 8 , and a l l t h e d a t a were used t o ca l cu - l a t e ave rages . see t h a t t h e h ighe r space v e l o c i t i e s produce a less a romat i c r e c y c l e d i s t i l l a t e . hydrogenat ion s e v e r i t y d e c r e a s e s wi th space v e l o c i t y t h i s was unexpected. The ga in i n a l i p h a t i c s between t h e Syncrude, Fuel O i l and In t e rmed ia t e space v e l o c i t i e s is seen i n t h e a l k y l a l p h a and gamma p r o t o n s , which measure long cha in a l i p h a t i c s , such as par- a f f i n s . These d i f f e r e n c e s i n d i s t i l l a t e composi t ion may r e f l e c t the f a c t t h a t lower d i s t i l l a t e y i e l d s a t t h e h i g h e r space v e l o c i t y mean t h a t t h e r ecyc le d i s t i l l a t e w i l l see more passes through t h e u n i t . Of c o u r s e , t h e o p e r a b i l i t y d i f f i c u l t i e s encountered i n PDU Run 8, and t h e i n t e n t i o n a l l y d iv ided n a t u r e of t h a t r u n , make f i r m conc lus ions u n l i k e l y .

Table 3 p r e s e n t s ave rage 'H-NMR d i s t r i b u t i o n s f o r The pe r iods of

Comparing f i r s t t h e r e s u l t s from Runs 5 and 8 (both I l l i n o i s 6 c o a l ) we S i n c e

PDU Run 9 (Kentucky 11 c o a l , Syncrude mode) g i v e s a less aromatic r e c y c l e d i s t i l - l a t e than PDU Run 5 ( I l l i n o i s 6 c o a l , Syncrude mode), though t h e d i f f e r e n c e is not as g r e a t a s between PDU Run 5 and t h e In t e rmed ia t e mode of PDU Run 8 . Apparen t ly , space v e l o c i t y has more e f f e c t on r e c y c l e d i s t i l l a t e composi t ion than feed c o a l .

Se l ec t ed samples of t h e r e c y c l e d i s t i l l a t e s from t h e t h r e e runs were used t o ex- t r a c t Indiana V coa l i n a microautoclave a t two s t a n d a r d c o n d i t i o n s . The r e s u l t s (Table 4 ) show t h a t a l l of t h e r e c y c l e d i s t i l l a t e s are good l i q u e f a c t i o n s o l v e n t s . The conversions t o TSF s o l u b l e s a r e g e n e r a l l y i v t h e 7 0 4 0 % range, and t h e s e r e s u l t s a r e i n d i c a t i v e of good l i q u e f a c t i o n s o l v e n t s ( ' ) . D i f f e r e n c e s which occur i n a given run , and among t h e d i f f e r e n t runs , i n d i c a t e t h a t r e c y c l e d i s t i l l a t e s produced i n t h e Syncrude mode a r e b e t t e r l i q u e f a c t i o n s o l v e n t s than t h o s e from e i t h e r t h e In t e rmed ia t e o r Fuel O i l modes. I n PDU Run 5 t h e r e was a g e n e r a l tendency toward improved s o l v e n t q u a l i t y a s t h e run p rogres sed . In PDU Run 9 t h e t r e n d i s r eve r sed , a l though t h e conve r s ions ob- t a i n e d wi th t h e PDU Run 9 d i s t i l l a t e s a r e e q u i v a l e n t t o o r b e t t e r t han t h o s e from PDU Run 5. For PDU Run R t h e two days shown compare conversions f o r d i s t i l l a t e s produced i n t h e Fue l O i l mode wi th d i s t i l l a t e s produced i n t h e In t e rmed ia t e mode o p e r a t i o n . The d i s - t i l l a t e s from t h e I n t e r m e d i a t e mode a r e c o n s i s t e n t l y poore r , and i n some c a s e s by a l a r g e margin, than those from the Fuel O i l mode. Th i s i s c o n s i s t e n t w i th d a t a shown i n Table 3 g i v i n g t h e average NMR d i s t r i b u t i o n s of t h e s e d i s t i l l a t e s , which show a s u r p r i s i n g l y high concen t r a t ion of a l k y l b e t a and gamma p ro tons f o r d i s t i l l a t e s produced a t t h e In t e rmed ia t e space v e l o c i t y .

While t h e r e c y c l e d i s t i l l a t e s were q u a l i t a t i v e l y s i m i l a r , the r e c y c l e r e s i d s (97SoF+, THF s o l u b l e ) showed a much g r e a t e r v a r i a t i o n i n composi t ion, p r i n a r i l y as a f u n c t i o n of

91

space v e l o c i t y . Tab le 5 shows t h a t t h e r e c y c l e r e s i d from PDU Runs 5 and 9 (Syncrude) averaged around 49% o i l s (hexane s o l u b l e s ) . The r e c y c l e r e s i d i n PDU Run 9 had a somewhat h i g h e r p r e a s p h a l t e n e and lower a s p h a l t e n e c o n t e n t t han t h e r e c y c l e r e s i d from PDU Run 5 . However, t h e r e c y c l e r e s i d i n PDU Run 8 showed much lower o i l s con ten t and much h i g h e r p reaspha l t enes con ten t t han f o r e i t h e r of t h e Syncrude r u n s . Th i s lower q u a l i t y r e c y c l e r e s i d i n PDU Run 8 may have been r e l a t e d t o ( e i t h e r a s cause o r e f f e c t ) t h e o p e r a b i l i t y problems which occurred i n t h a t run.

APPROACH TO STEADY STATE RECYCLE COMPOSITION

The d a t a from PDU Runs 5 and 9 a l low u s t o draw s e v e r a l conc lus ions concerning t h e approach t o a s t e a d y s t a t e r e c y c l e s l u r r y oil d u r i n g t h o s e two runs. Because of t h e fragmented n a t u r e of PDU Run 8 we a r e not a b l e t o draw any conc lus ions concerning s t eady s t a t e ope ra t ion from t h e d a t a f o r t h a t run. The m a j o r i t y of t h e d a t a from PDU Runs 5 and 9 i n d i c a t e s t h a t t h e r e c y c l e r e s i d composi t ion, b u t n o t t h e r e c y c l e r a t e , reached s t e a d y state between days 10 and 15. The r e c y c l e r e s i d composi t ion i n PDU Run 5 does show some v a r i a t i o n a f t e r day 20 of t h a t r u n , when t h e hydrogen p a r t i a l p r e s s u r e was inc reased from a n ave rage of 1600 p s i g f o r the f i r s t 20 days of t h e run t o an average of 1860 p s i g d u r i n g t h e l a s t 10 days. However, t h i s appea r s t o be an adjustment t o a new equ i l ib r ium composi t ion a s opposed t o a long t e r m v a r i a t i o n i n t h e r e c y c l e r e s i d composi t ion. The p l o t of t h e r a t i o of benzene s o l u b l e s t o i n s o l u b l e s i n t h e THF s o l u b l e r e c y c l e r e s i d du r ing PDU Runs 5 , 8 and 9 (F igu re 2) demonstrates t h i s conc lus ion .

In c o n t r a s t t o t h e behavior of t h e r e c y c l e r e s i d composi t ion, t h e r e c y c l e rate of t h e r e s i d d id n o t r each s t e a d y s ta te i n PDU Run 9 . This i s i l l u s t r a t e d i n Figure 3 , which shows t h e r e c y c l e r a t e s of o i l s , a s p h a l t e n e s and p reaspha l t enes on a l b / l b c o a l fed b a s i s . day 12 , t h e p l o t s are n e a r l y p a r a l l e l a f t e r t h a t p o i n t . However, a l l t h r e e show s t e a d y i n c r e a s e s throughout t h e 30-day run . t h a t t h e p r e a s p h a l t e n e r e c y c l e r a t e reached an appa ren t s t eady s t a t e by about day 25. These r e s u l t s a r e impor t an t s i n c e a s t e a d i l y i n c r e a s i n g r e s i d r e c y c l e r a t e t ends t o reduce t h e appa ren t r e s i d y i e l d from t h e u n i t . The re fo re , t h e r e c y c l e composi t ion can have a d i r e c t and immediate impact on t h e pe rce ived u n i t performance.

Because t h e composi t ion of t h e r e c y c l e r e s i d reached s t e a d y s t a t e by about

A more r i g o r o u s t r ea tmen t of t h e d a t a ( 6 ) shows

Two measures of t h e r e c y c l e d i s t i l l a t e composi t ion, t h e r a t i o of a romat i c t o a l i - p h a t i c p ro tons , and t h e c o n c e n t r a t i o n of phenolic-OH in t h e c l e a n o i l t a n k , a r e shown i n F igu res 4 and 5 , r e s p e c t i v e l y . These d a t a demons t r a t e t h a t t h e r e c y c l e d i s t i l l a t e composi t ion d i d no t r e a c h s t eady s t a t e i n PDU Run 9 . The da ta on samples from PDU Run5 i n d i c a t e a s t e a d y s t a t e r e c y c l e d i s t i l l a t e composi t ion sometime nea r t h e midpoint of t h a t run. However, t h e d a t a from PDU Runs 5 and 9 a r e ve ry s i m i l a r up t o about day 20 of t hose r u n s , and t h e behav io r of t h e samples from PDU Run 5 a f t e r day 20 may have been in f luenced by i n c r e a s e d hydrogen p a r t i a l p r e s s u r e , a s d i s c u s s e d above. i n c r e a s e i n hydrogen p a r t i a l p r e s s u r e would tend t o dec rease bo th t h e a romat i c - to -a l i - p h a t i c r a t i o and t h e c o n c e n t r a t i o n of phenolic-OH. Th i s could compensate f o r d e c l i n i n g c a t a l y s t a c t i v i t y a t t h e end of PDU Run 5.

Note t h a t an

These d a t a and o t h e r s concerning t h e approach of t h e r e c y c l e r e s i d and d i s t i l l a t e composi t ions t o s t e a d y s t a t e i n d i c a t e t h a t the r a t e of c a t a l y s t d e a c t i v a t i o n f o r t h e l a r g e r r e s i d molecules i s more r a p i d than t h e r a t e of c a t a l y s t d e a s t i v a t i o n f o r t h e smaller d i s t i l l a t e molecules . w i th r e s p e c t t o conve r s ion of t h e r e s i d t o d i s t i l l a t e r ange m a t e r i a l by day 10-15 of both PDU Runs 5 and 9 . t h e d i s t i l l a t e i s s t i l l d e c l i n i n g a t t h e end of t h e 30 day run.

In o t h e r words t h e c a t a l y s t has reached a s t e a d y s t a t e

However, t h e c a t a l y s t a c t i v i t y w i t h r e s p e c t t o hydrogenat ion O f

CONCLUSIONS

The major c o n c l u s i o n s drawn from t h i s work a r e :

S t a r t u p s o l v e n t i s r a p i d l y r ep laced i n PDU o p e r a t i o n . Any a romat i c s t a r t u p s o l v e n t of t h e a p p r o p r i a t e b o i l i n g r ange should s u f f i c e i f i t is p h y s i c a l l y compatible .

92

0 Aromat ic i ty of r e c y c l e o i l i n c r e a s e s dur ing run wi th d e c l i n i n g c a t a l y s t a c t i v - D i s t i l l a t e a r o m a t i c i t y reached s t e a d y s ta te i n PDU 5 but n o t i n PDU 9 , i t y .

perhaps because of i n c r e a s e d PH, a f t e r day 20 of PDU 5 . hydroxyl c o n t e n t s of r e c y c l e d i s t i l l a t e s .

Same i s t r u e f o r

0 Composition of r e c y c l e r e s i d reached s t e a d y s ta te i n PDU Runs 5 and 9 , by about day 1 2 , b u t changed i n Run 5 c o i n c i d e n t wi th i n c r e a s e d P H ~ .

Recycle r a t e of r e s i d d i d not reach s t e a d y s ta te i n PDU 9 , a l though composi- t i o n d i d . S i t u a t i o n i n PDU 5 w a s complicated by i n c r e a s e d PH,.

Recycle r e s i d i n PDU 8 was much h i g h e r i n p r e a s p h a l t e n e s than PDU 5 o r 9 , p robably r e l a t e d t o o p e r a b i l i t y problems.

0 Recycle d i s t i l l a t e s were q u a l i t a t i v e l y s i m i l a r r e g a r d l e s s of mode or c o a l . A l l a r e good l i q u e f a c t i o n media.

0 PDU 5 and 9 d a t a i n d i c a t e a f a s t c a t a l y s t d e a c t i v a t i o n f o r r e s i d hydrogena- t i o n (10-15 days) and a s lower c a t a l y s t d e a c t i v a t i o n f o r d i s t i l l a t e hydrogena- t i o n (> 30 d a y s ) .

Kentucky 9 and I l l i n o i s 6 c o a l s g i v e s i m i l a r s l u r r y r e c y c l e o i l s a t t h e Syn- c rude mode. D i f f e r e n c e s among Fuel O i l , I n t e r m e d i a t e and Syncrude space v e l o c i t i e s , wi th same c o a l , are g r e a t e r .

T h i s work was suppor ted by U . S . DOE Cont rac t DE-AC05-79ET14503.

REFERENCES

Johanson, E . S. and Comolli , A . G . , "PDU Run 9 , Syncrude Mode Opera t ion With Cata- l y s t Addi t ion and Withdrawal, Kentucky 11 Coal," U.S. DOE Cont rac t EX-77-C-01-1547, ? l i l e s t o n e Report ( D r a f t ) , FE/2547-50, March 19'30.

Johacson, E . S. and Comolli , A . G . , "PDU Run 5 , Syncrude Node Opera t ion With Cata- l y s t Addi t ion and Withdrawal," U.S. DOE Cont rac t EX-77-C-01-2547, M i l e s t o n e Repor t , FE-2547-19, J u n e 1978.

Johanson, E . S . and Comolli , A. G . , "PDIJ Run 8 , Fue l O i l and I n t e r m e d i a t e Mode Oper- a t i o n With C a t a l y s t Replacement," U.S. DOE Cont rac t EX-77-C-01-2547, F i l e s t o n e Repor t , FE-2547-46, December 1979.

Burke, F. P . , Winschel, R . A. and Pochapsky, T. C . , "Development of a C o r r e l a t i o n Between S l u r r y O i l Composition and Process Performance," U . S . DOE C o n t r a c t DE-AC05- 79ET-14503, T o p i c a l Report No. 1, DOE/ET-14503-1, A p r i l 1980.

Burke, F. P . , Winschel, R . A . and Pochapsky, T . C . , "Development of a C o r r e l a t i o n Between S l u r r y O i l Composition and Process Performance," U . S . DOE Cont rac t DE-ACO5- 79ET-14503, Topica l Report No. 2 , DOE/ET-14503-2, August 1980.

Burke, F. P . , Winschel, R . A . and Pochapsky, T . C . , "Development of a C o r r e l a t i o n Between S l u r r y O i l Composition and Process Performance," U . S . DOE C o n t r a c t DE-ACO5- 79ET-14503-3, F i n a l Repor t , DOE/ET-14503-3, January 1981.

K l e i n p e t e r , J . A . , Burke, F. P . , Dudt, P . J . and J o n e s , D . C . , "Process Development f o r Improved SRC Options: Shor t Residence T i m e S t u d i e s , " EPRI P r o j e c t 1134-1, F i n a l Repor t , EPRI AP-1425, June 19x0.

93

Table 1

H-Coal PDU Runs S tudied

PDU Run

5

8

9

Coal

I l l i n o i s 6

I l l i n o i s 6

Kentucky 11

Space V e l o c i t y ( l b / h r - f t 3 ) Mode Opera t ions Note

3 1 (Syncrude)

78 (Fuel O i l ) Opera t ing problems caused

Increased PH, a f t e r day 20.

50-65 ( I n t e r m e d i a t e ) by plugging.

3 1 (Syncrude) Uneventful.

Table 2

A n a l y t i c a l Techniques

'H-NMR (COT, HO D i s t i l l a t e , HO Res id) - Hydrogen D i s t r i b u t i o n s - Donatable Hydrogen

LIQUID CHROMATOGRAPHY (HO Resid) - S o l v e n t F r a c t i o n a t i o n ( O i l s , Asphal tenes , P r e a s p h a l t e n e s ) - Chemical F u n c t i o n a l i t i e s - Molecular S i z e D i s t r i b u t i o n

GC/MS AND REVERSE PHASE L I Q U I D CHROMPTOGKAPHY (COT and HO D i s t i l l a t e s ) - D e t a i l e d Compositional Analys is - C h a r a c t e r i s t i c Parameters

"F-DERIVATIZATION AND "F-NMR - Hydroxyl (OH) Content

MICROAUTOCLAVE - E m p i r i c a l Measure of Solvent Q u a l i t y

T a b l e 3

Average 'H-NMR D i s t r i b u t i o n s of Hydroclone Overflow Di s t i l l a t e s

Averane 'H-N?% D i s t r i b u t i o n s ,

PDU Run - Per iod

Hydroclone Overflow Di s t i l l a t e s Cond. Uncond. C y c l i c Alkyl C y c l i c Alkyl

Mode ~ - L A ~ B _ Y _ A r A r B 5 12-30 Syncrude 26.7 11.1 17.3 12.2 11.9 13.5 7.3

8 3-15 F u e l O i l 26.6 9 .2 17.5 11.9 12.2 15.3 7.3 8 17-21 I n t e r m e d i a t e 21.6 5 . 6 16.5 11.5 12.5 19.4 9.5

9 10-26 Syncrude 22.4 9 .7 17.5 12.2 13.6 16.2 8.4

94

Table 4

Microautoclave Extractions of Indiana V Coal With H-Coal Recycle Distillates - Conversion to THF Solubles, Wt % MAF Coal

PDU RUN

Sample

EQ Conditions

KIN Conditions

5 8 9

HO COT

Day Day 3 80.6 69.8 --

12 79.6 76.5 13 25 77.9 77.3 20 Avg 79.4 74.5

3 76.3 74.8 -- 12 80.8 74.3 1 3

HO COT

Day 3

73.8 72 .3 19 72.9 6 2 . 3 26 73.4 67.3

-- --

- _ _

2 82.7 73.6 19 -- --

25 83.3 75.0 20 70.4 68.9 26 Avg 80.1 74.7 75.6 71.2

HO

85.7 79 .9 77.6 81.1

78.2 78.7 79.8 78.9

COT

81.0 76.8 75.9 77.9

75.3 72.7 73.9 74.0

-

EQ - 750"F, 30 min, 211 solventlcoal KIN - 750"F, 10 min, 811 solvent/coal

Table 5

Solubility Fractionation of Hydroclone Overflow THF Soluble Resids

PDU Average, wt % THF Soluble Resid - Run Period Mode Oils Asphaltenes Preasphaltenes

5 12-30 Syncrude 49.0 32.9 18.1

8 11-15 Fuel Oil 28.4 32.8 38.8 8 17-23 Intermediate 33.7 33.6 32.7

9 10-30 Syncrude 48.5 27.4 24. 1

95

I I I I I I Pun P*?/,<

I o -

Figure 3

LCF Separation o f HO THF Soluble Resid H-Coal POU Run 9

o i l s

L . _L -1 20 3 0

Day I

96

f igure 5

Concentratlon of PhenolIc -OH by "F-IMR COT Samples

H-Coal PDU Runs 5. 8 and 9

figure 4

Rat io o f A m M t t c l R l i p h a t i c Protons, Total Recycle D i s t i l l a t e H-Coal POU Run 5 and 9

PDU Run 9 ~

:/ ; f -

- : .I

---; -' -.: . - : - L r

POU Run 9 r- 3 i

97

THE OCCURANCE OF AUTOGENIOUS WATER-GAS SHIFT REACTION ON HYDROGENATION OF SUB- BITUMINOUS COALS. M. Gawlak, D. Carson, H. Wasylyk. B. Ignasiak, A l b e r t a Research Counci l 11315 - 87 Avenue, Edmonton, A l b e r t a , Canada, T5G 2C2.

Two subbituminous A l b e r t a Coals (21-22% 0, on da f ma t te r ) were l i q u e f i e d i n a cont inuous u n i t , i n a recyc le mode, w i t h hydrogen. Independently, autoc lave l i que - f a c t i o n t e s t s were c a r r i e d o u t i n hydrogen us ing r e c y c l e so l ven t from continuous l i q u e f a c t i o n as a medium. The r e s u l t s revealed t h a t i n bo th cases from IO-30% o f the hydrogen consumed on l i q u e f a c t i o n (4-6% by weight o f d a f coa l ) was used up f o r genera t i on o f water. However, when the same coals were l i q u e f i e d i n autoc lave under s i m i l a r cond i t i ons bu t i n anthracene o i l , a water-gas s h i f t r e a c t i o n occurred which r e s u l t e d i n n e t consumption o f water in t roduced w i t h coal i n t o autoc lave. The r e s u l t s are t e n t a t i v e l y i n t e r p r e t e d i n terms o f d i f f e r e n t a c i d i t y o f so lvents i n r e l a t i o n t o meta ls contents o f t h e t r e a t e d coa ls .

98

SOLVENT EFFECTS I N EXXON DONOR SOLVENT COAL LIQUEFACTION. P. Maa, K. L. Trachte, and R. Wi l l iams. Exxon Research & Engineer ing Co., P.O. B o X L i n d e n NJ 07036.

The Exxon Donor Solvent (EDS) coal l i q u e f a c t i o n process u t i l i z e s a wide range of

Exxon Research ti Engineering Co., P.O. Box 4265, Baytown TX 77520.

coal ranks, from l i g n i t i c t o bituminous, and produces a v a r i e t y o f l i q u i d p roduc t s l a t e s under moderate process ing cond i t i ons . The r e c y c l e o f hydrogenated, coal de r i ved so l ven t i s a key t o t h e performance o f t h e EDS Process.

The r o l e o f t h e r e c y c l e so l ven t i n EDS i s t o p rov ide a convenient v e h i c l e for t r a n s p o r t i n g coal i n t o the process, t o d isperse t h e coal , and t o donate hydrogen t o f r e e r a d i c a l s produced by t h e thermal r u p t u r e o f chemical bonds. The hydrogen donat ing c a p a b i l i t y o f t h e r e c y c l e so l ven t a l l o w s a balanced u t i l i z a t i o n o f bo th donor as w e l l as molecular hydrogen under moderate process ing cond i t i ons . conversion i n t h e l i q u e f a c t i o n reac to r , product s e l e c t i v i t y can be c o n t r o l l e d t o prov ide e i t h e r predominantly naphtha o r d i s t i l l a t e product s l a t e s .

L i q u e f a c t i o n s tud ies have been conducted i n smal 1 batch autoc laves and i n t e g r a t e d p i l o t u n i t s i n o rde r t o b e t t e r understand so lvent-coal i n t e r a c t i o n s i n t h e EDS Process. Resul ts o f these s tud ies w i l l be discussed i n t h i s paper.

I n a d d i t i o n , t h rough s o l v e n t

99

UPGRADING COAL LIQUEFACTION RECYCLE BOTTOMS

H. F. Silver, R . L . Mi l le r and R. G . Corry Chemical Engineering Department

R . J . Hurtubise Chemistry Department

Un ive r s i ty o f Wyoming, Laramie, Wyoniing 82071

INTROOUCTION

In both the EDS and t h e SRC-I1 d i r e c t coal l i q u e f a c t i o n processes, d i s t i l l a t e y i e l d s have been increased s i g n i f i c a n t l y by inc luding vacuum column bottoms product i n t h e recyc le so lven t . upgraded in the EDS process , no s p e c i f i c e f f o r t i s made t o upgrade t h e non- d i s t i l l a b l e por t ion o f t h e r ecyc le so lvent i n either the EDS nor the SRC I 1 processes . A study was t h e r e f o r e i n i t i a t e d a t t h e Univers i ty of Wyoming t o determine t h e e f f e c t o f upgrading coal l i que fac t ion recyc le bottoms.

EXPERIMENTAL PROCEDURE Liquefaction of both subbituminous Wyodak and bituminous Kentucky coa ls has been s tudied i n a t w o - l i t e r Autoclave Magnedrive-I1 batch r eac to r . Samples o f Wyodak c o a l , Wyodak coal der ived r ecyc le so lven t , and so lven t r e f ined coa l , SRC, were supplied by C a t a l y t i c , Inc . from the Southern Serv ices Inc. p i l o t p lan t a t Wilson- v i l l e , Alabama. Samples of Kentucky coa l , Kentucky coal derived recyc le so lvent and SRC were suppl ied by the P i t t sbu rg &Midway Coal Mining Co. from t h e i r p i l o t p l an t near Tacoma, Washington.

Por t ions o f the r ecyc le so lven t s bo i l i ng above 533K were used as received while o t h e r por t ions were mi ld ly hydrogenated over a Co-Mo on A1203 c a t a l y s t (Nalcomo 477) f o r 60 minutes a t 644K using an i n i t i a l cold r e a c t o r hydrogen pressure of 13 .8 MPa. Por t ions o f t he SRC were used a s rece ived while o ther por t ions were upgraded by so lven t f r a c t i o n a t i o n and by hydrogenation. The SRCs were so lvent f r ac t iona ted i n t o cyclohexane s o l u b l e o i l s , cyclohexane inso luble - benzene so lub le asphal tenes , benzene s o l u b l e o i l s plus asphal tenes and benzene inso luble-pyr id ine so lub le preasphal tenes . Por t ions o f the SRCs and t h e i r o i l plus asphal tene f r a c - t i o n s were mi ld ly hydrogenated over c a t a l y s t a t 64@K f o r 60 minutes using an i n i t i a l co ld r eac to r hydrogen pressure o f 13.8 MPa. genated over c a t a l y s t a t 700K f o r 60 minutes using an i n i t i a l cold r e a c t o r hydrogen pressure of 20.7 MPa.

Coal l i que fac t ion experiments were then conducted by charging the r e a c t o r w i t h recyc le so lven t , SRC o r SRC f r a c t i o n and coal i n a 1 : l : l weight r a t i o . The reac- t i o n was c a r r i e d out a t 714K f o r 60 minutes using an i n i t i a l co ld r eac to r hydrogen pressure of 13 .8 MPa. Gaseous products were analyzed using an HP 5840 gas chromatograph. Unreacted coal and mineral mat te r were determined by soxh le t e x t r a c t i o n s u s i n g pyr id ine . All -runs were dup l i ca t ed ,

DISCUSSION O F RESULTS

The ex ten t o f coal l i q u e f a c t i o n in t h i s work was measured using percent 700Kt conversion, X700, def ined by the r e l a t i o n s h i p

While t h e d i s t i l l a b l e por t ion of the r ecyc le so lven t i s

Other por t ions were severe ly hydro-

Liquid products were d i s t i l l e d using a modified ASTM-D 1160 appara tus .

'IN - "OUT '700 = 'IN

100

where

and

A summary of t h e conversions obtained us ing d i f f e r e n t so lvents i s presented i n Table I . - + 1.0% of the mean values repor ted i n t h i s tab le .

Examination o f t he r e s u l t s f o r so lvents 1-6, con ta in ing Wyodak coa l der ived SRC, and so lvents 12-16, con ta in ing Kentucky coal der ived SRC, suggest t h a t maximum conver- s ions are obtained i f the SRC i s m i l d l y hydrogenated. The da ta obtained from Wyo- dak so lvents 4, 5 and 6, and f o r Kentucky so lvents 13, 14 and 16 suggest t h a t SRC component e f fec t i veness may pass through a maximum as hydrogenation s e v e r i t y i s increased. Comparison o f so l ven t 3 w i t h so lvent 5 and so l ven t 15 w i t h so l ven t 16 suggests t h a t t he observed increases i n conversion r e l a t i v e t o so lvents 1 and 12 a r e due more t o m i l d l y hydrogenated SRC than m i l d l y hydrogenated d i s t i l l a t e .

While the r e l a t i v e l y h igh conversion obtained frm so lven t 2 cou ld be a t t r i b u t e d t o the c a t a l y t i c a c t i v i t y o f t he ash i n t h i s sample o f u n f i l t e r e d SRC, ash found i n Wyodak coal i s genera l l y no t considered t o be a c a t a l y s t f o r t he coal l i q u e f a c t i o n reac t ion . us ing so lvent 2 i s t he lower i n i t i a l b o i l i n g p o i n t o f the h igh ash SRC as compared t o the f i l t e r e d SRCs. I n o rder t o reduce t h i s v i s c o s i t y , some o f t he normal ly d i s t i l l a b l e l i q u i d s were n o t removed from t h e h igh ash SRC du r ing d i s t i l l a t i o n .

The r e s u l t s shown i n Table I a lso suggest t h a t so l ven t f r a c t i o n a t i o n may a l s o improve the l i q u e f a c t i o n e f fec t i veness o f SRCs. 17-19 suggest t h a t l i t t l e , i f any, improvement i n Kentucky coa l so lvent e f f e c t i v e - ness can be obtained by hydrogenating the benzene so lub le o i l s p lus asphaltenes obtained from Kentucky SRC.

L i q u i d y i e l d s and hydrogen consumption depend upon the ex ten t o f coa l conversion. Net l i q u i d y i e l d s o f C4-533K and 533-7OOK from Wyodak coal as a percent o f the MF coal a re presented i n Figures 1 and 2 as a f u n c t i o n o f X700. Po in ts presented on these and the f o l l o w i n g f i g u r e s a re i d e n t i f i e d by the number i n Table I i d e n t i f y i n g the so l ven t used i n the experiment. As would be expected, l i q u i d y i e l d s inc rease w i t h inc reas ing X7 o. S i m i l a r p l o t s o f l i q u i d y i e l d s fo r Kentucky coal a re p re - sented i n Figures 3 and 4. For comparison purposes, the s o l i d l i n e s i n Figures 1 and 2 have been reproduced as dashed l i n e s i n F igu res3and 4, respec t i ve l y , so t h a t d i r e c t comparisons can be made between Wyodak and Kentucky coa l y i e l d s . seen i n Figures 3 and 4, Kentucky coal produced g rea te r l i q u i d y i e l d s than Wyodak coa l a t low conversions. two coals a re q u i t e comparable.

Hydrogen consumptions f o r bo th Wyodak and Kentucky coal experiments are presented i n Figures 5 and 6. hydrogen consumed i n upgrading e i t h e r the d i s t i l l a b l e so l ven t nor the SRC o r SRC f r a c t i o n s . I t has been est imated t h a t hydrogen consumed i n t h i s manner would be i n the order o f 1.0 t o 2.0 w t % o f t he MAF coa l charged t o t h e reac to r .

CONCLUSIONS

Resul ts ob ta ined from t h i s work i n d i c a t e the importance of so l ven t composi t ion on t h e coal l i q u e f a c t i o n reac t i on . Through the a d d i t i o n of m i l d l y hydrygenated SRC t o a recyc le so lvent , f o r example, ne t C4-700K l i q u i d y i e l d s approaching 60 w t % o f t he MF coal charged t o a batch reac to r were obtained from both Wyodak and Kentucky coa ls used i n t h i s study.

WIN = grams o f MAF coa l p lus grams o f SRC o r SRC f r a c t i o n p lus grams o f

WOUT= grams o f MAF 700K+ product recovered from t h e reac to r .

The average r e p r o d u c i b i l i t y o f conversions f o r dup l i ca ted runs was w i t h i n

700K+ d i s t i l l a t e charged t o the reac to r .

A more reasonable exp lanat ion f o r t he h igh conversion observed when

I n the p i l o t p l a n t , ash increases the v i s c o s i t y o f SRC.

Resul ts obtained using so lvents

As can be

However, a t h igh conversions, t h e l i q u i d y i e l d s from the

The consumptions shown i n these f igures do no t i nc lude t h e

101

A c e r t a i n amount o f bottoms r e c y c l e upgrading may occur i n d i r e c t l y i n processes such as the EDS process w i t h bottoms recyc le o r t he S R C - I 1 process. However, i t may be poss ib le t o o b t a i n even f u r t h e r increases i n d i s t i l l a t e y i e l d s by d i r e c t upgrading o f a bottoms recyc le , e i t h e r by hydrogenation o r by so l ven t f rac t i ona t ion . It should be po in ted o u t t h a t these hypotheses a re based on batch reac to r runs, s i m u l a t i ng cont inuous coa l 1 i que fac t i on opera t ion . De le te r ious compounds could b u i l d up i n r e c y c l e streams i n cont inuous p lan ts t h a t were no t observed i n t h i s s tudy .

ACKNOWLEDGEMENTS

M r . Ronald B o r g i a l l i and Mrs. Jane Thomas have made subs tan t i a l con t r i bu t i ons t o t h i s program. The work has been c a r r i e d o u t under DOE Contract No. DE-ACO1- 79ET14874.

Further work i n t h i s area appears t o be warranted.

TABLE I X700 CONVERSION RELATED TO THE DEGREE OF SOLVENT HYDROGENATION

SOLVENT

x,oO ( % I DISTILLABLE NONDISTILLABLE SOLVENT NO. PORTION PORTION

WYODAK 1 2

3 4 5

6

7 8 9

10

11

UH(l) UH

UH MH MH

MH

UH MH MH

UH

UH

KENTUCKY 12 UH 13 MH 14 MH 15 UH 16 MH

17 UH 18 MH 19 MH

NOTES : UH = Unhydrogenated MH = M i l d l y Hydrogenated SH = Severely Hydrogenated O+A= O i l s p lus Asphaltenes A = Asphaltenes 0 = O i l s

SRC, UH 23.8 (SRC+Ash), UH 36.5

SRC, M H ( ~ ) 42.5 SRC, MH 35.8 SRC, UH 32.0

SRC, SH(3) 27.2

( o + A ) ( ~ ) , UH 28.4

(O+A), SH 29.0

A(5) , UH 34.6

(O+A) , WH 37.4

0(6), UH 35.9

SRC, UH 28.5 SRC, MH 39.9 SRC, SH 36.4 SRC, MH 38.8 SRC, UH 30.5

(O+A) , UH 35.5 (O+A) , MH 37.0 (O+A), SH 37.0

102

\ \ \

n .\\ \s?

' u \ \ \ \ \ \ \ \

I I 1

\

J I I I

0

h x L

\

\ \ \ \ \ \ \

I L

4 8 G

7- I I I

-

\ J I I I

m N 0 P 0 0 0

0 In

0 *

0 h

x

L 0

0

U

Y

rn VI

VI w

m -

N

m

m o z N

103

I I

20 30 40 50

X 700 O/o

Figure 5 . Hydrogen Consumption f o r Wyodak Coal a s a Funct ion of X700

I I 1 1

0 0

,

0 0

0 0,

14 A:," I I 1 1

20 30 40 50

X 7001 OIo

Figure 6 . Hydrogen Consumption f o r Kentucky Coal a s a Funct ion o f x700

104

COAL LIQUEFACTION WITH SELECTIVE HEAVY RECYCLE. C. J. K u l i k , H. E. Lebowitz, and W. Weber. E l e c t r i c Power Research I n s t i t u t e , 3412 H i l l v i e w Avenue, P.U. Box 10412,

Palo A l t o CA 94303.

E a r l i e r EPRI programs have shown t h e e f f e c t s o f r e c y c l i n g a l i g h t vacuum bottoms ( s o c a l l e d " L i g h t SRC") stream as p a r t o f t h e so l ven t f o r coal l i q u e f a c t i o n . v ious work showed t h a t t h e L i g h t SRC recyc le r e s u l t e d i n improved performance, p a r t i c u - l a r l y a t r e l a t i v e l y low temperatures, below 800OF. The prev ious work cons is ted o f comparat ive ly s h o r t runs i n which t h e r e c y c l e streams were no t e q u i l i b r a t e d ; t h e ash separa t i on and vacuum bottoms f r a c t i o n a t i o n were n o t i n t e g r a t e d w i t h t h e c o a l l i q u e - f a c t i o n . The r e s u l t s were thus somewhat t e n t a t i v e .

Several runs have now been completed a t t h e W i l s o n v i l l e 6 t o n p e r day coal l i q u e - f a c t i o n p i l o t p l a n t which s u b s t a n t i a l l y con f i rm the p rev ious f i n d i n g s , and add i n t e r e s t - i n g data rega rd ing t h e scale-up from semi-continuous t o cont inuous opera t i on . paper w i l l d iscuss t h e p i l o t p l a n t r e s u l t s and r e l a t i o n s h i p between t h e two scales o f operat ion.

The p re -

Th is

105

ROLE OF THE AROMATIC OXIDATIVE COUPLING REACTION I N FUEL CHEMISTRY

J. B. P i e rce

Department o f Chemistry Univers i ty o f Lowell Lowell, Massachusetts 01854

3

I n t h e temperature range o f 300' t o 5OO0C bituminous c o a l s pas s through one o r more p l a s t i c s t a g e s , bu t a f t e r each occurrence continued h e a t i n g causes s o l i d i f i c a t i o n (1). I n t h e d i r e c t l i q u e f a c t i o n of c o a l s o r p rocess ing o f coa l -der ived l i q u i d s a t p y r o l y t i c tempera tures c a t a l y t i c s u r f a c e s become fouled wi th carbonaceous d e p o s i t s (2 ,3,4) . I n j e t f u e l s the presence o f he t - e rocyc l i c a r o m a t i c compounds con ta in ing n i t rogen i n the r i n g s causes sludge t o f o r m ( 5 ) . Carbazoles and r e l a t e d compounds tend t o f o r m carbonaceous e l e c t r o d e d e p o s i t s a t anodes i n e l ec - t rochemica l c e l l s .

Each of t h e s e e f f e c t s is caused by an inc rease i n molecular weight which might a r i s e f r o m a number o f d i f f e r e n t chemical r e - a c t i o n s . However, i n t hese s p e c i f i c ox ida t ion- reduct ion r e a c t i o n s a favored o x i d a t i o n h a l f r e a c t i o n i s the oxidat ive coupling o f a r o m a t i c r i n g s t r u c t u r e s . The f i r s t c l u e t o the ope ra t ion of a r o m a t i c ox ida t ive coupling as a rou te t o products o f h ighe r mol- e c u l a r weight and lower s o l u b i l i t y r e s u l t e d from the observa t ion o f e l e c t r o d e f i l m formation on anodes when coa l -der ived l i q u i d s were being examined e l ec t rochemica l ly ( 6 ) .

EXPERIMENTAL

The e l e c t r o d e f i lms formed by anthracene o i l and SRC-I1 type product o i l s der ived f r o m B l a c k s v i l l e No. 9 c o a l were s tud- i e d by means of c y c l i c voltammetry and double p o t e n t i a l s t e p chronoamperometry. A Pr ince ton Applied Research Model 170 Elec- t rochemis t ry System was employed. The e l e c t r o l y t e w a s t e t r a b u t y l ammonium f l u o r o b o r a t e , and so lven t s were a c e t o n i t r i l e f o r the anthracene o i l and t e t r ahydro fu ran f o r SRC-I1 type product o i l s .

DISCUSSION

Anthracene o i l and many samples o f SRC-I1 type product o i l f r o m t h e 1000 pound p e r day p i l o t p l a n t a t P i t t s b u r g h Energy Technology Center ( P E E ) were examined e l ec t rochemica l ly and found t o f o r m e l e c t r o d e d e p o s i t s under oxidizing cond i t ions . Successive voltammetric t r a c e s show the i n s u l a t i n g e f f e c t o f the f i l m depos i ted by an thracene o i l (Figure l a ) . Progress ive chang- ing of t h e swi tch ing p o t e n t i a l toward more cathodic p o t e n t i a l s shows a decrease (F igu re lb) and e l imina t ion (Figure IC) of the f i l m - f orming tendency, 3 Work done a t P i t t s b u r g h Energy Technology Center , P.0. Box 10940, P i t t s b u r g h , Pennsylvania 15236.

106

In a d i f f e r e n t experiment t h e i n i t i a l p o t e n t i a l o f an SRC-I1 type s o l u t e was held a t +1.000 v o l t f o r d i f f e r e n t l eng ths o f t i m e , and the r e s u l t i n g f i l m s were reduced i n the voltammetric scan toward more cathodic p o t e n t i a l s . The peak he igh t s r e f l e c t the c u r r e n t s used t o reduce the f i l m s formed by ox ida t ion a t +1.000 v o l t . A l i n e a r v a r i a t i o n i n peak he igh t w i th time i s shown (Figure 2 ) . I n these samples the f i l m s a r e much more r e - ac t ive than those formed f r o m anthracene o i l .

The f i l m s formed on anodes proves the r e a c t i o n t o be an oxidat ion. The formation of e l e c t r o d e f i l m s , which, depending on cond i t ions , va r i ed from s o f t , brown, and so lub le t o hard, g l o s s y , b l ack , and inso lub le i n p y r i d i n e , proves an inc rease i n molecular weight. The presence of r e a c t i v e aromatic s t r u c t u r e s i n c o a l s and coa l -der ived l i q u i d s ( 7 ) suggests the ope ra t ion o f the aromatic oxidat ive coupling r e a c t i o n . Table I comprises a l i s t o f s e l e c t e d compounds t h a t undergo ox ida t ive coupling.

anthracene, C H aromatic ox ida t ive coupling proceeds by way o f a r a d i c a l E2t2811 intermediate . Oxidations:

A s r epor t ed by Dworkin and o t h e r s ( 8 ) and i l l u s t r a t e d wi th

C14H10 - C14H10 + e- Cl4HlO + Cl4HI0 -+- C28H10 + 2H' + 2e-

C14H10 + 2H+ + 2e- --t C14H12 Net Reaction:

3C14H10 - C28H18 + '1bH12 Many common reagen t s and c a t a l y s t s cause r a d i c a l c a t i o n formation which i n i t i a t e aromatic oxidat ive coupling. These include H SO ( 9 , l O ) , ox id i z ing a e n t s i n a c i d i c media ( 9 , 1 1 , 1 2 , 1 3 ) ~ Lewis &i$s (14-261, halogens 727'1, Ag(C10 and iod ine ( 2 8 , 2 9 ) , and meta l salts (30 ,31 ) . Free r a d i c a l c a t i o n s a r e a l s o formed by such s o l i d c a t a l y t i c su r faces as gamma-alumina ( 3 2 ) , s i l i c a alumina ( 3 3 ) , and z e o l i t e s (34). They may a l s o be genera ted by pho to ion iza t ion (35,36,37) and e lec t rochemica l ox ida t ion (38) . Both r a d i c a l cat- ions and r a d i c a l anions were genera ted a t P E E by e l e c t r o l y s i s o f SRC-I1 type s o l u t e s i n an ESR c a v i t y ( 3 9 ) .

I n suppor t o f t h i s information Ross and Bless ing r e p o r t , " I n the absence o f an H-donor, t hen , ox ida t ive c r o s s l i n k i n g t akes p l ace wi th in the c o a l upon hea t ing , y i e l d i n g a product even l e s s so lub le i n so lven t s such as pyridine than w a s the s t a r t i n g coal" (40). Others have r epor t ed the same behavior ( 4 1 , 4 2 ) . Thus, one may conclude t h a t Lewis a c i d s cause ox ida t ive hydrogen t r a n s f e r from hydrogen donors o r oxidat ive polymer iza t ion through a sequence of coupling r eac t ions . Other r a d i c a l c a t i o n forming c a t a l y s t s and r eagen t s may be expected t o behave s i m i l a r l y .

Reduction :

CONCLUSIONS

Aromatic s t r u c t u r e s may polymerize by a s tepwise, oxida- t i v e coupling r e a c t i o n , i n i t i a t e d by formation of r a d i c a l c a t - ions. Common reagents and c a t a l y s t s cause r a d i c a l c a t i o n s t o f o r m .

107

REFERENCES

1.

2.

3.

4.

5 .

6.

7.

8.

9.

IO.

11.

12.

13

14.

15 16. 17

18.

19 20.

Davis, J . D , , Reynolds, D . A . , Naugle, B.W., Wolfson,D.E., and Birge, G . W . , Technical Paper 726, U.S. Department o f the In- t e r i o r , U.S. Government P r i n t i n g Off ice , 1949. K r i z , J .F. , and Ternan, M. A.C.S. Div. Fuel Chem. P r e p r i n t s , Vol.25, No. 2, p 146, March 24-28, 1980. Sivasubramanian, R . , Olson, J . H . , and K l a t z e r , J . R . , A.C.S. Div. Fuel Chem. P r e p r i n t s , V o l . 25, No. 1, p 86, March 24-28, 1980; w. p 149. Shih , S.S. , Angevine, P . J . , Heck, R . H . , and Sawruk, S . , A.C. S. Div. Fuel Chem. P r e p r i n t s , V o l . 25, No. 1, p 154, March

Frankenheld, J . W . , and Taylor , W.F., A.C.S. Div. Fuel Chem. P r e p r i n t s , Vol . 23, No. 4, p 205, September 10-15, 1978. P i e r c e , J . B . , "New Approsches i n C o a l Chemistry", A.C.S. Symposium S e r i e s , Ed. by Blaus te in , B.D. , Bockrath, B.C. , Friedman, S . , and Retcofsky, H.L. ( i n p r e s s ) . P h i l i p , C . V . , and Anthony, R . G . , A.C.S. Div. Fuel Chem. Pre- p r i n t s , V01.24, No. 3, p 204-14, September 10-14, 1979. Dworkin, A,S., Poutsma, M.L. , Brynestad, J . , Brown, L . L . , G i l p a t r i c , L .O . , and Smith, G.P., J. Am. Chem. SOC. 1979,

24-28, 1980.

- 101, 5299. H o i j t i n k , G . J . , and Weijland, W.P., Rec. Trav. Chim., 1957, 26, 836- Carr ington , A , , Dravnieks, F . , and Symons,'M.C.R., J. Chem. Soc. , 1961, 905. MacLean, C . , and Van der Waals, J . H . , J. Chem. Phys. , 1957 3, 287- Aalbersberg, W.I., Gaaf, J. , and Mackor, E . L . , J. Chem. SOC. 1961, 905, Dal l inga , G . , Mackor, E.L., and V e r r i j n S t u a r t , A . A . , Mol . Phys. , 1958, 1, 123. Weissman, S . I . , de Boer, E. , and Conradi, J .J . , J. Chem, Phys.

Lewis, I . C . , and S i n g e r , L.S., J. Chem. Phys. , 1965, 3, 2712. Lewis, I . C . , and S i n g e r , L.S. , J.Chem. Phys. 1966, w , 2082. 1957, 26, 963.

Forbes, W.F., and S u l l i v a n , P.D., J. Am. Chem. SOC. , 1966, - 88, 2862. Shine, H . J . , and S u l l i v a n , P.D., J. Phys, Chem., 1968, 72,

S u l l i v a n , P.D., J. Am. Chem. S O C . , 1968, 90, 3628. Buck, H.M. , Bloemhoff , W . , and Oosterhoff , L. J. , Tetrahedron L e t t . a, 5 .

1390

108

21. Rooney, J .J . , and Pink, R . C . , Proc. Chem. S O C . , lq61, 142. 22. S a t o , H . , and Aoyama, Y . , Bul l . Chem. SOC. Japan, 1973, 4.6,

631. 23. Forbes, W.F., and S u l l i v a n , P.D., J. Am. Chem. S O C . , 1966, - 88, 2862. 24. B e l l , F..A. , Ledwith, A. , and Sher r ington , D . C . , J, Chem.

SOC. (B), 1969, 2719. 25. Aalbersberg, W.I., H o i j t i n k , G . J . , Mackor, E.L., Weij land,

W.P., J. Chem. S O C . , m, 3055. 26 Buchanan, 111, A . C . , Dworkin, A.S., Brynstad, J . , G i l p a t r i c k ,

L .O . , and Smith, G . P . , J. Am. Chem. SOC. 1979, 101, 5430. 27. F i t z g e r a l d , Jr., E.A., Wuefling, Jr., P . , and R i c h t o l , H.H.

J. Phys. Chem., 1971, 21, 2737. 28. S a t a , Y . , Kinoshi ta , M. Sano, M . , and Akamatu, H . , Bul l .

Chem. SOC. Japan, 1969, 42, 548, 3051. 29. Ris tagno, C . V . , and Shine , H . J . , J. Org, Chem., 1971, SI

4050. 3 0 . Heiba, E . I . , Dessau, R.M. , and Koehl, Jr. , W . J . , J. a m . Chem.

31. Dessau, R . M . , Shih, S . , and Heiba, E . I . , J. Am. Chem. S O C . ,

32. F lockhar t , B .D . , S c o t t , J . A . N . , and Pink, R . c . , Trans. Fara-

33. Rooney, and Pink, R . C . , Trans. Faraday SOC. 1962, 2, 1632. 34. K u r i t a , Y . , Sonoda, T., and S a t a , M. J. Catalysis, 1970,

35. Lewis, G.N., and Lipkin , D . , J. Am. Chem. SOC. , 1942, &,2801. 36. Lewis, G . N . , and Bige le i sen , J . , J. Am. Chem. SOC. 1943, a,

Soc. 1969, z1 6830.

1970, 92, 412.

day S O C . , 1966, 62, 730.

u, 82.

2419. 37. Land, E . J . , and P o r t e r , G . , Trans. Faraday S O C . , 1963, 2,

2016, 2027. 38. Bard, A . J. , Ledwith, A . , and Shine , H. J. , "Advances i n Phy-

s i c a l Organic Chemistry", Vol. 13, Ed. b t V. G o l d and D. B e t h e l l , Academic P r e s s , 1976, pp. 156-278.

39. Sprecher , R.S., and P i e r c e , J . B . , Unpublished Work, 1980. 40. R o s s , D.S., and Blessing, J . E . , A.C.S., Div. F u e l Chem. Pre-

41. LOW, J . Y . , and ROSS, D.S., A.C.S., Div. Fue l Chem. P r e p r i n t s ,

42. Mobley, D.P., Salim, S . , Tanner, K . I . , Taylor , N . D , , and

p r i n t s , V o l . 24, No.2, p 130, Apr i l 2-6, 1979.

V o l . 22, No. 7 , p 1 2 1 , August 29-September2, 1977.

B e l l , A.T. , A.C.S. , Div. Fuel Chem. P r e p r i n t s , V o l . 23, No. 4 , p 138, September 10-15, 1978.

109

43. Osa, T. , Y i l d i z , A. , and Kuwana, T . , J. Am. Chem. SOC. ,

44. Nyberg, K . , Acta Chemica Scandinavica 1970, &, 1609. 45. Bobbi t t , J . M . , Weisgraber, K . H . , S t e i n f e l d , A.S., and

46. Bobbi t t , J . M . , Yagi, H . , Shibuya, 3. , and Stock, J . T . , J.

47. Bobbi t t , J . M . , Noguchi, I . , Yagi, H . , and Weissgraber, K.H.,

1969, 9 1 1 3994.

Weiss, S.G., J. Org. Chem. , 1970, 2, 2884.

O r g . Chem., 1971, s, 3006.

J .Am. Chem. SOC., 1971, p2, 3551. 48. Bech a a r d , K . , and Parker , V . D . , J. Am. Chem. SOC., 1972,

5% $749 49. Nelson, R.F. , and Adams, R . N . , J. Am Chem. SOC. , 1968, 90,

3925. 50. Marcoux, L.S., Adams, R . N . , and Feldberg, S.N., J. Phys.

51. Nelson, R . F . , and Feldberg, S.W., J. Phys, Chem., 1969,

52. Bacon, J. and Adams, R . N . , J .Am. Chem. SOC. 1968, 90, 6596. 53. Ambrose, J . F . , Carpenter , L . L . , and Nelson, R.F., J. Elec-

trochem. SOC., 1975, 122, 876. 54. Ambrose, J . F . , and Nelson, R.F., J. Electrochem. SOC.,

1968, 115, 1159. 55. Frank, S.N., Bard, A . J . , and Ledwith, A , , J. Electrochem.

Soc, 1975, 122, 898. 56. S o l i s , V., Iwasita, T . , and Giordano, M . C . , J. ElectroefiaJ1..

Chern, 1975, 105, 169. 57. Jordan, J. , Ankabrandt, S. J . , Robat, A , , and S t u t t s , J . D . ,

Abst rac t No. 133, 12th C e n t r a l Regional Meeting, Am. Chem. SOC. , P i t t s b u r g h , Pa . , November 12-14, 1980.

Chem. 1969, 22, 2611.

2 2 1 2623.

110

Table I

Compounds Susceptible to Oxidative Coupling compounds References

Benzene 43 p - Xylene 44 Mesitylene 44 Durene 44 Phenolic Tetrahydro- isoquinolines 45 46 47 Catechol Ethers 48

Compounds Triphenylamines 4.9 50 51 Anilines 52 Carbazoles 53 154 Iminobibenzyls 55 o-Phenylenedianine 56 Dibenzothiophene , 57

1.ov

Figure 2. Effect of Film Formation on Voltammo- -gram of SRC-I1 Type Liquids.

Figure 1. Effect of Film Formation on Voltammograms of Anthracene Oil.

111

Low Temperature Hydrogenation of Polycycl ic Aromatic Hydrocarbons (PAH's) by T e t r a l i n in a Molten S a l t Cata lys t*

A . C. Buchanan, 111, A. S. Dworkin, L. L. Brown, and G. P. Smith

Chemistry Div is ion , Oak Ridge National Laboratory P. 0. Box X , Oak Ridge, Tennessee 37830

Molten SbC13 h a s been shown t o be an e f f e c t i v e c a t a l y s t f o r t h e hydrocracking of coa l with a h igh s e l e c t i v i t y f o r t h e production of d i s t i l l a t e hydrocarbons (1). analogous t o the more ex tens ive ly s tud ied molten salt hydrocracking c a t a l y s t s based on ZnC12 (2 ,3 ) . Our r e sea rch is aimed a t a b a s i c study of molten s a l t c a t a l y s i s w i th r ecen t s t u d i e s examining t h e chemical behavior of PAH's (model compounds f o r some of the s t r u c t u r a l u n i t s of coa l ) i n molten s a l t s i n which SbC13 is the primary cons t i t uen t (4-7). We have observed r e a c t i o n s f o r PAH's i n SbC13 based melts in which the anhydrous SbC13 so lven t is involved c a t a l y t i c a l l y (4) and stoichiomet- r i c a l l y (5,6). r e a c t i o n s i n the m e l t i n which Sb3+ is a n oxidant .

Both types of chemistry have been explained by redox dr iven

T e t r a l i n is o f t e n used a s a hydrogen donor so lvent f o r thermally generated n e u t r a l r a d i c a l s i n c o a l l i q u e f a c t i o n and model compound s tud ie s . In the p re sen t work, we i n v e s t i g a t e t h e p o s s i b i l i t y t h a t t e t r a l i n may a c t as a hydrogen donor t o some PAH's under extremely mild (8OoC, no H2) molten sal t c a t a l y t i c cond i t ions i n which PAH r a d i c a l c a t i o n s are be l ieved t o be p re sen t as r eac t ive in te rmedia tes .

We have s tud ied the r e a c t i o n behavior of phenanthrene, pyrene, an thracene , and naphthacene(tetracene)with t e t r a l i n a t 8 0 ° C i n nea t a p r o t i c SbC13 by in s i t u 1 H NMR, and by determining the r e a c t i o n s to ich iometry v i a product a n a l y s i s follow- i n g quench and sepa ra t ion procedures. A l l r eagents w e r e ca re fu l ly p u r i f i e d (4,5), and ma te r i a l t r a n s f e r s were c a r r i e d out i n a con t ro l l ed argon atmosphere dry box. 1 H NMR experiments (at 200 MH,) were performed under argon i n sea led 5m OD tubes whi le l a rge r s c a l e r e a c t i o n s were performed under argon i n Schlenk glassware. Following a 30 min r e a c t i o n per iod , the r e a c t i o n mixture was hydrolyzed with 6 M H C l and the o rgan ic products were ex t r ac t ed i n t o CH2C12. i n these r e a c t i o n s , and no antimony meta l was eve r observed. from the r e a c t i o n of an thracene wi th t e t r a l i n i n SbC13 were analyzed by GC-MS us ing a 30 m x 0.25 mm I D g l a s s c a p i l l a r y column wi th an OV-101 l iqu id phase. Quan t i t a t ive r e s u l t s were obta ined by GC using a 10' x 1/8" column packed wi th 3% Dexs i l 300 and flame i o n i z a t i o n de tec t ion . Hexamethylbenzene w a s used a s an i n t e r n a l s t anda rd , and t h e r e s u l t s were co r rec t ed f o r d i f f e rences i n de t ec to r response.

SbC13 is a c a t a l y s t The organic products

Solu t ions of pyrene and phenanthrene with t e t r a l i n do not r e a c t i n neat SbC13 a t 80°C. even a t temperatures up t o 130'C. However, anthracene and naphthacene r e a c t r ap id ly with t e t r a l i n a t 80°C, and a r e s e l e c t i v e l y hydrogenated t o 9,lO-dihydroanthracene (DHA) and 5,12-dihydronaphthacene (DHN) r e spec t ive ly . DHA and DHN were i d e n t i f i e d from a comparison of t h e i r l H NMR spec t r a wi th those of a u t h e n t i c samples (4 ) .

Only the NMR s p e c t r a of t he pa ren t PAH and t e t r a l i n a r e observed

* Research sponsored by the Div is ion of Chemical Sciences, Off ice of Basic Energy Sciences, U. S . Department of Energy under con t r ac t W-7405-eng-26 wi th the Union Carbide Corporation.

112

The r e a c t i o n of anthracene with t e t r a l i n i n SbCl i s c u r r e n t l y the most ex tens ive ly s tud ied . T e t r a l i n i t s e l f is unreac t ive i n SbC13 (8O-13O0C), and anthracene a l s o does not show any r eac t ion i n SbC13 a t 80°C f o r t h e 30 min reac- t i o n per iod . A t longer r eac t ion per iods , anthracene slowly undergoes Schol l condensation r eac t ions t h a t w e have previous ly repor ted ( 4 ) . This Schol l r e a c t i o n . is be l ieved t o proceed through the anthracene r a d i c a l ca t ion . In the presence of t e t r a l i n , however, anthracene does not undergo Schol l condensation but i n s t ead is rap id ly hydrogenated by t e t r a l i n . 'H NMR experiments us ing f u l l y deutera ted anthracene demonstrate t h a t t h e hydrogens added a t the 9 and 10 pos i t i ons of anthracene (63.99) a r e from the t e t r a l i n . This observa t ion is supported by t h e q u a n t i t a t i v e a n a l y s i s of t e t r a l i n , anthracene, and DHA in the organic products from l a r g e r s c a l e reac t ions .

3

The product d i s t r i b u t i o n and r eac t ion stoichiometry are found t o depend on the amount of t e t r a l i n i n i t i a l l y present . with increas ing amounts of t e t r a l i n and reaches a maximum of 39% a t a 2 : l t e t r a l i n : anthracene mole r a t i o (Table 1). Furthermore, we f i nd from GC-MS t h a t t h e dehydrogenated t e t r a l i n does no t produce naphthalene. Ins tead i t forms p r i n c i p a l l y two condensed products 1 (MW = 262) and $ (MW = 308) whose r e l a t i v e amounts a l s o depend on the i n i t i a l amount of t e t r a l i n present a s shown i n Table 1. The o v e r a l l r eac t ion s to ich iometry can be described a s the sum of two l i m i t i n g equations wi th Equation 1 predominating a t high t e t r a l in / an th racene mole r a t i o s and Equation 2 predominating a t low t e t r a l in / an th racene mole r a t i o s .

We f ind t h a t t h e y i e l d of DHA i nc reases

1 5

We a r e i n t h e process of determining the s t r u c t u r e s of & and 2, and these r e s u l t s should provide use fu l c l u e s towards understanding the r eac t ion mechanism.

Although anthracene and naphthacene a r e hydrogenated by t e t r a l i n i n SbClj, phenanthrene and pyrene a r e unreac t ive . phenanthrene and pyrene a r e not ox id ized by SbC13 t o r a d i c a l ca t ions , whereas t h e more e a s i l y oxidized PAH's, anthracene and naphthacene, do form r a d i c a l ca t ions i n SbC13. These r e s u l t s , along wi th our previous observa t ions of redox dr iven r e a c t i o n s i n SbC13 i n which Sb3+ a c t s a s an oxidant (4-6), suggest t h a t t he unusual low temperature hydrogenation r e a c t i o n s repor ted here proceed v i a r e a c t i o n of t h e PAH r a d i c a l c a t i o n wi th t e t r a l i n . Research i n t h i s area is continuing i n an e f f o r t t o f u r t h e r e l u c i d a t e the r e a c t i o n mechanism.

From a previous ESR study (7) w e know t h a t

REFERENCES

1. Wald, M. M . ; U.S. Patent 3 542 665, 1970. 2. Z ie lke , C . W . ; S t ruck , R. T . ; Evans, J. M . ; Costanza, C . P . ; Gorin, E.

Ind. Eng. Chem. Process. Des. Dev. 196!!, 2, 151, 158; Zie lke , C . W . ; Klunder, E. B . ; Maskew, J. T . ; S t ruck , R. T. H. m 0 , 2, 85.

3. Ida , T . ; Nomura, M . ; Nakatsu j i , Y ; Kikkawa, S. Fuel 1979, E, 361. 4. Dworkin, A. S . ; Poutsma, M. L . ; Brynestad, J . ; Brown, L. L . ; G i lpa t r i ck , L. 0.;

5. Buchanan, A. C . , 111; Dworkin, A . S. ; Smith, G. P . J. Am. Chem. SOC. 1980, 102, 6. Buchanan, A. C . , 111; Dworkin, A. S . ; Smith, G . P. J . Org. Chem. 1981, 46, 471. 7.

Smith, G. P. J. Am. Chem. SOC. 1979, 101, 5299.

5262.

Buchanan, A. C . , 111; Liv ings ton , R . ; Dworkin, A. S. ; Smith, G. P- J. Phys. Chem. E O , 86, 423.

Table 1. Inf luence of T e t r a l i n Concentration on the Ant hracene-Te t r a l i n - SbCl React ion0

3 .

~~ ~ ~~~~ ~~

k12 mole r a t i o ' b T e t r a l i n ( m o l ) Anthracene (mmol) DHA y i e l d (%)

0

0.70

1.40

2.80

5.60

1.40

1.40

1.40

1.40

1.40

0

20

30

39

38

-

. I5

-50

1.5

3.5

'Reactions were run i n 34.2 mmol SbCl

bBased on o r i g i n a l an thracene (?2%).

a t 80°C f o r 30 min. 3

'Based only on gc a r e a r a t i o s .

114

Copper Cata lyzed Aging Reac t ions of a SRC 11 Middle Dis t i l l a te

Laudie Jones and Norman C . L i

Duquesne U n i v e r s i t y , P i t t s b u r g h , PA 15282

INTRODUCTION

S t a b i l i t y of s y n f u e l s i s an impor tan t c o n s i d e r a t i o n i n d i r e c t u t i l i z a t i o n o r upgrading p r o c e s s e s . The tendency of s y n f u e l s t o form gums and s e d i - ments and t o i n c r e a s e i n v i s c o s i t y poses a s e r i o u s de t r iment i n handl ing procedures and burning e f f i c i e n c y . Recent ly , i n v e s t i g a t o r s have s t u d i e d t h e aging c h a r a c t e r i s t i c s of s h a l e (1) and coa l -der ived l i q u i d s (2-5) i n an a t tempt t o i d e n t i f y t h e r e a c t i v e components and t o p o s t u l a t e mechanisms. I n ag ing s t u d i e s of a S y n t h o i l p roduct i n an oxygen atmosphere , t h e v i s c o s i t y i n c r e a s e w a s accompanied by a decrease i n t h e con- t e n t o f o i l components and i n i n c r e a s e i n the conten t of benzene- inso l - ub le components ( 4 ) . S i m i l a r r e s u l t s were observed i n a s tudy o f a SRC I/SRC I1 blend aged by bubbl ing oxygen d i r e c t l y i n t o t h e sample ( 6 ) . These s t u d i e s f n d i c a t e t h a t dur ing o x i d a t i v e degrada t ion , the o i l components ' r e a c t t o form benzene- inso luble components which are p r i m a r i l y r e s p o n s i b l e f o r t h e i n c r e a s e d v i s c o s i t y .

The o x i d a t i v e degrada t ion of a SRC-II middle d i s t i l l a t e , which i s an o i l , f r e e o f a s p h a l t e n e s and benzene- inso lubles w a s i n v e s t i g a t e d i n t h i s s t u d y . The o b j e c t i v e w a s t o determint. t h e molecular types of compounds r e s p o n s i b l e f o r t h e v i s c o s i t y change and p o s t u l a t e mechanisms. S i n c e t h e middle d i s t i l l a t e i s r e l a t i v e l y s t a b l e t o o x i d a t i v e d e g r a d a t i o n , copper shavings were added t o a c c e l e r a t e t h e p r o c e s s .

EXPERIMENTAL

SRC I1 middle d i s t i l l a t e ( b . p . range , 170-276OC) from I l l i n o i s n o . 6 c o a l was obta ined from Gulf R&D C o . , and from a process r u n o p e r a t e d a t 2000 p s i hydrogen p r e s s u r e a t 454OC f o r 1 h r r e s i d e n c e t ime. The c o a l l i q u i d was p laced i n a 3-necked f l a s k , equipped w i t h a gas bubbl ing i n l e t and a condenser t o minimize t h e l o s s of v o l a t i l e s . Oxygen w:s bubbled through t h e sample (1-2 ml/min) and copper shavings , 2 w t t o ,

were added t o a c c e l e r a t e t h e degrada t ion . The f l a s k was immersed i n a thermosta t b a t h a t 620C. and samples were withdrawn a t time i n t e r v a l s , f o r v i s c o s i t y and o t h e r measurements.

Separa t ion of Aged Coal Liquid i n t o Pentane-Soluble and Pentane- Inso l - ub le Components :

Pentane , 20- fo ld by volume, w a s added t o t h e aged c o a l l i q u i d , mixed (magnetic s t i r r i n g b a r ) f o r 1 h r a t room temperature and then f i l t e r e d through a 0 .5 micron m i l l i p o r e s t y r e n e membrane. The p r e c i p i t a t e w a s d r i e d i n a vacuum oven a t 800 f o r 1 2 h r t o remove pentane (94% of t h e p r e c i p i t a t e i s s o l u b l e i n benzene) . Pentane from t h e pentane-so luble f r a c t i o n was remove? by d i s t i l l a t i o n a t 4OOC. The sample was t h e n sub- j e c t e d t o r o t a r y evapora t ion a t 700 f o r 5 rnin t o i n s u r e complete removal of pentane.

INSTRUMENTATION

V i s c o s i t y d a t a were o b t a i n e d a t 300 u s i n g a Brookf ie ld S y n c h r o l e c t r i c 115

viscometer w i t h a s m a l l Sam l e a d a p t o r . I n f r a r e d s p e c t r a o f CS s o l u - t i o n s (5g/L) i n a 5 mm K B r P i q u i d c e l l were o b t a i n e d w i t h a Becgman IR-20 spectrometer. MHz spec t rometer a s CDC13 s o l u t i o n s w i t h TMS as i n t e r n a l r e f e r e n c e . G e l permeat ion chromatograms were o b t a i n e d w i t h a Waters HPLC and t h r e e p - s t y r a g e l columns i n s e r i e s : 103, 500, and 100 A us ing THF as s o l v e n t a t a flow ra te o f 1 ml/min.

NMR s p e c t r a were o b t a i n e d w i t h a 6o-MHz o r 600-

RESULTS AND DISCUSSION

V i s c o s i t y of t h e c o a l l i q u i d i n c r e a s e d e x p o n e n t i a l l y w i t h t i m e when aged a t 62OC w i t h oxygen and copper . 620 does n o t a f f e c t t h e v i s c o s i t y i n a 5-day p e r i o d . Thus, t h e loss of v o l a t i l e s which undoubtedly occurs w i t h oxygen bubbl ing through t h e sample does not c o n t r i b u t e t o t h e observed v i s c o s i t y change.

I n f r a r e d s p e c t r a of d i l u t e s o l u t i o n s of t h e c o a l l i q u i d b e f o r e and a f t e r ag ing 5 days a t 620 w e r e ob ta ined . The unaged c o a l l i q u i d shows a prom- i n e n t f r e e hydroxyl s t r e t c h i n g band a t 3600 c m - 1 . The i n t e n s i t y of t h i s band i s n o t s i g n i f i c a n t l y a f f e c t e d by ag ing w i t h copper o r oxygen a l o n e . Aging w i t h both copper and oxygen, however, reduces t h e i n t e n s i t y of t h i s band. This i n d i c a t e s t h a t t h e hydroxyl group i s modif ied d u r i n g a g i n g .

The unaged c o a l l i q u i d i s completely s o l u b l e i n pentane . A f t e r ag ing 5 d a y s , 30% of t h e aged c o a l l i q u i d becomes i n s o l u b l e i n pentane . T h e r e f o r e , pentane w a s used t o s e p a r a t e t h e aged material i n t o two f r a c - t i o n s : t h e p e n t a n e - s o l u b l e and pentane- inso luble f r a c t i o n s .

Comparison of t h e 60 MHz NMR s p e c t r a of t h e c o a l l i q u i d b e f o r e and a f t e r ag ing 4 days shows t h a t f o r t h e aged pentane-so luble f r a c t i o n : (a ) there is a decrease i n t h e i n t e n s i t y of t h e s i g n a l a t 2 . 3 ppm a t t r i b u t e d t o t h e methyl pro tons a t t a c h e d t o b e n z y l i c groups , (b) t h e hydroxyl s i g n a l a t 5 ppm i s a b s e n t , and (c ) t h e h i g h e r - f i e l d a romat ic s i g n a l s from 6 . 3 t o 6 . 8 ppm are a l s o a b s e n t . The 600-MHz s p e c t r a of t h e unaged c o a l l i q u i d and i t s a c i d - f r e e f r a c t i o n (obta ined by i o n exchange Chromatography) a r e p r e s e n t e d i n F i g . 1. The a c i d - f r e e spectrum i s i d e n t i c a l t o t h a t of t h e aged pentane-so luble f r a c t i o n (not shown). Obviously, dur ing ag ing , a c i d i c methyl s u b s t i t u t e d phenols a r e modif ied and a r e no longer s o l u b l e i n pentane .

The g e l permeat ion chromatographv o f t h e unaged c o a l l i q u i d shows t h r e e peaks ( r e t e n t i o n t i m e s of -28, 23 and 30 min.) A f t e r ag ing f o r t h r e e days , p r o f i l e s of t h e pentane-separa ted f r a c t i o n s (F ig . 2) show t h a t t h e aged pentane-so luble f r a c t i o n ( t o p ) , which c o n s t i t u t e s 70 w t Z o f t h e aged c o a l l i q u i d , c o n t a i n s components which e l u t e a t 29 and 30 min. Com- ponents o f t h e unaged c o a l l i q u i d which e l u t e a t 23 n i n a r e no longer p r e s e n t a f t e r ag ing . t h e unaged c o a l l i q u i d ( i s o l a t e d by ion-exchange chrora tography) a l s o e l u t e a t 28 min. The p r o f i l e of t h e pentane- inso lubleZrac t ion (F ig . 2 bottom) shows t h a t t h i s f r a c t i o n i s composed of l a r g e n o l e c u l a r s i z e components. These r e s u l t s sugges t t h a t t h e p o l a r c o n s t i t u e n t s o f t h e c o a l l i q u i d a r e r e a c t i n g dur ing ag ing t o form l a r g e molecular aggrega tes which a r e p e n t a n e - i n s o l u b l e .

The c o a l l i q u i d was a l s o e n r i c h e d 10 w t % w i t h a c i d i c and b a s i c f r a c - t i o n s which were i s o l a t e d by ion-exchange chromatography. The e f f e c t of t h e s e a d d i t i v e s on t h e format ion of p e n t a n e - i n s o l u b l e material is shown i n Table 1. The e n r i c h e d c o a l l i q u i d s were aged a t 62OC f o r 1 day w i t h oxygen and 1% copper .

Aging w i t h copper o r oxygen a l o n e a t

A s comparison, t h e a c i d i c and b a s i c components of

C l e a r l y , enrichment w i t h the a c i d I1 f r a c t i o n 116

y i e l d s t h e l a r g e s t amount of p e n t a n e - i n s o l u b l e material (46 w t % ) . a c i d - I 1 f r a c t i o n c o n s i s t s of a l k y l s u b s t i t u t e d p h e n o l s , t h e base I1 f r a c t i o n c o n t a i n s q u i n o l i n e t y p e compounds and t n e a c i d 1 f r a c t i o n con- t a i n s c a r b a z o l e s , i n d o l e s , a n i l i n e s and xylenols (5).

The e lementa l composition of t h e c o a l - l i q u i d b e f o r e and a f t e r aging 4 days i s p r e s e n t e d i n Table 2 . The aged pentane-so luble f r a c t i o n con- t a i n s 23;b l e s s oxygen and 50% less n i t r o g e n than t h e unaged c o a l l i q u i d . The decrease i n oxygen c o n t e n t i s c o n s i s t e n t w i t h IR, NMR, and GPC re- s u l t s showing a r e d u c t i o n i n t h e amount of phenol ic compounds dur ing ag ing . The l a r g e amount of oxygen conta ined i n t h e p e n t a n e - i n s o l u b l e f r a c t i o n i n d i c a t e s : (a ) oxygen c o n t a i n i n g compounds of t h e c o a l l i q u i d have been c o n c e n t r a t e d i n t h i s f r a c t i o n and (b) t h e oxygen bubbled i n t o t h e c o a l l i q u i d h a s been i n c o r p o r a t e d i n t o t h e s t r u c t u r e of t h i s f r a c - t i o n . This i s confirmed i n FTIR s p e c t r a (not shown). The i n c r e a s e d n i t r o g e n c o n t e n t of t h e pentane- inso luble f r a c t i o n i n d i c a t e s t h a t n i t r o g e n c o n t a i n i n g compounds are involved i n the ag ing r e a c t i o n .

S i g n i f i c a n t c h a r a c t e r i s t i c s of the aged pentane-so luble f r a c t i o n a r e t h a t t h e v i s c o s i t y and t h e atomic H J C r a t i o a r e s i m i l a r t o t h o s e o f t h e unaged c o a l l i q u i d , b u t t h e oxygen and n i t r o g e n c o n t e n t s a r e l e s s (Table 2 ) . A low heteroatom content i s r e q u i r e d i n syncrude upgrading procedures t o prevent f o u l i n g of t h e c a t a l y s t . Our experiments have shown t h a t a r e d u c t i o n i n heteroatom c o n t e n t can be achieved w i t h m e t a l l i c copper under mi ld c o n d i t i o n s .

The r e s u l t s of t h i s s tudy sugges t t h a t a t l e a s t one of t h e ag ing r e a c - t i o n s i s t h e s e l e c t i v e polymer iza t ion of phenol ic compounds. I n c o r - p o r a t i o n of oxygen and polymer iza t ion of n i t r o g e n compounds a l s o o c c u r . I n o x i d a t i v e coupl ing of phenols , -OH groups g ive way t o e t h e r l i n k a g e s , i n t h e formation of polymers. The d i s t i n c t l y s m a l l e r r e t e n t i o n t ime of t h e pentane- inso lubles i n t h e GPC p r o f i l e s and t h e i n c r e a s e d VPO molecu- l a r weight of t h e p e n t a n e - i n s o l u b l e s a r e c o n s i s t e n t w i t h t h e format ion of polymers.

The

ACKNOWLEDGEMENTS

We acknowledge suppor t of t h e U . S . Department o f Energy under Cont rac t No. DE-AC22-80 PC 30252. Mellon U n i v e r s i t y , suppor ted by PHS Grant No. RR-00292, was used , and w e thank K . S . Lee and J . Dadok f o r e x p e r t advice i n c a r r y i n g o u t t h e Iti MIR measurements.

The 600 MHz NMR spec t rometer a t Carnegie-

REFERENCES

C.J . Nowack, R . J . Del Fosse , G. Speck, J . Solash and R.N. H a z l e t t , P r e p r i n t , Div. Fue l Chem., Am. Chem. S O C . , 25 ( 3 ) , 40 (1980) . Y.Y. L i n , L . L . Anderson, and W . H . Wiser, P r e p r i n t , Div. Fue l Chem., Am. Chem. S O C . , 19 ( 5 ) , 2 (1974) . D . F i n s e t h , M . H E g h , J . A . Q u e i s e r , and H.L. Retcofsky, P r e p r i n t , Div. P e t r o l . Chem. Am. Chem. S O C . , 24 ( 4 ) , 979 (1979) . F.R. Brown and F .S . Karn, F u e l , 5 9 , 7 3 1 (1980). D.W. Brinkman, J . N . Bowden, J . W . T r a n k e n f e l d , and W.F. T a y l o r , P r e p r i n t , Div. F u e l Chem., Am. Chem. S O C . , 25 ( 3 ) , 110 (1980) . T . Hara, L . Jones , N . C . L i , and K . C . T e w a r i u n p u b l i s h e d r e s u l t s .

11 7

Table 1. Aging of Enr iched Coal L iqu ids

(6ZoC, 1% Cu, 0 2 , 1 Day)

Pentane Inso lub le s

I11 #6 10% Acid-Free Enriched 10 Acid I Enr iched 10% Acid I1 Enr iched 10% Base I1 Enr iched

14% 10 11 46 12

Tab le 2 . Elemental Composition and C l i a rac t e r i za t ion o f SP.C I1 Yiddle D L s t i l l a t e , Before and A f t e r Aging 4 days , 2 w t % Copper and Oxygen a t 62OC

Unaged Aged Pentme-Soluble Aged Pentane-Insolubles

C 85 .58 86,. 67 H 9.12 9 . 3 3 N 0 .85 0 4.29 s 0.19

0 .43 3 .31 0.27

75.48 6.00 1 .80

12 .78 0 .27

100 .03 1 0 0 . 0 0 96.29

Copper MW 172*

Viscos i ty+ 4 . 3 Atomic H j C 1 . 2 8

170** 3 .6 1 .28

2 . 7 5 70*"*

0.96

*VPO method, t o l u e n e , 37OC 2-15 g / l

***VPO method, p y r i d i n e , 8 6 0 C . 4-7 g / l +Cen t ipo i se a t 30OC

* W P O method, methylene c h l o r i d e , 280C, 4-7 g / l

w

z d

a LL I-

- u i n. N

I a n

7

119

- 1 -

THE OXIDATION OF FUEL O I L #6 STUDIED BY

DIFFERENTIAL SCANNING CALORIMETRY

J . A . Ayala and M.E. Rincdn I n s t i t u t o de I n v e s t i g a c i o n e s ElEct r icas ,

Depar tamento de Combustibles F d s i l e s , Apdo. P o s t a l 475, Cuernavaca, Mor.,

Mexico.

INTRODUCTION

The s t u d i e s on combustion of heavy f u e l o i l a r e impor t an t because o f t h e ex tended u s e o f t h i s f u e l as an ene rgy source f o r t h e p r o d u c t i o n o f e l e c t r i c i t y , W i t h t h e con t inuous i n c r e a s e i n t h e e x t r a c t i o n o f p r o d u c t s from c r u d e o i l , t h e r e e x i s t s a c o n t i n u o u s d e g r a d a t i o n i n the q u a l i t v o f t h e r e s i d u e t h a t is t o be burned i n a u t i l i t v b o i l e r . The d e q r a d a t i o n of t h e q u a l i t y i n t h e r e s i d u a l o i l , means a h i q h e r s u l f u r c o n t e n t i n t h e f u e l , h i g h e r a r o m a t i c i t y , and h i g h e r a s p h a l t e n e and metal l ic c o n t e n t . Some o f t h e s e s p e c i e s , y i e l d p r o d u c t s o f combustion which are a g g r e s s i v e t o b o t h t h e envi ronment , and s o m e of t h e components w i t h i n t h e b o i l e r . It i s b e l i e v e d (1) t h a t an u n d e r s t a n d i n g of why and how p o l l u t a n t s form, must come from a n u n d e r s t a n d i n g of t h e chemica l k i n e t i c s i n the flame. That is, i n order t o p r o t e c t t h e env i ronmen t , and i n c r e a s e t h e a v a i l a b i l i t y o f a l a r g e b o i l e r more research i s needed t o unders tand t h e c h e m i s t r y o f o x i d a t i o n o f complex f u e l mix tu res .

Var ious a u t h o r s (2-6) have p o i n t e d o u t t h e p o t e n t i a l i t y o f t h e d i f f e r e n t t e c h n i q u e s i n the rma l a n a l y s i s f o r t h e

c h a r a c t e r i z a t i o n o f pe t ro lum p r o d u c t s and coal. However, v e r y l i t t l e k i n e t i c i n f o r m a t i o n has been e x t r a c t e d f rom t h e s t u d i e s which i n v o l v e t h e u s e o f t h e r m o a n a l v t i c a l t e c h n i q u e s . The' chemica l k i n e t i c s of thermo-oxida t ive p r o c e s s e s i n f u e l s , may c o n t r i b u t e t o a l a r g e e x t e n t t o t h e u n d e r s t a n d i n g o f t h e c h e m i s t r y

120

Of oxidation of such mixtures. Weber ( 2 ) , has reported the potencial utilization of differencial thermal analysis (DTA) to obtain kinetic parameters for the oxidation of hydrocarbons. He concluded, though, that for the kinetics of oxidation of heavy fuel oil no theory for DTA could yet be used, because of the complexity of the thermograms. Adonyi ( 3 1 , has shown that kinetics may be obtained for petroleum products by means of DTA, and thermogravimetric techniques (TG). More recently, Noel and Cranton ( 4 ) , have measured the activation energy, Ea, for the oxidation of lube oil by differential scanning calorimetry (DSC). These authors make the observation that more research is necessary in order to have a better understanding of the results observed by DSC. Smith et al. (7), have used TG to measure the rate, and the Ea for the oxidation of sixty-six coal samples. Valayavin et al. ( 8 1 , utilized TG to study the thermolysis of high molecular weight petroleum residues, and established a reaction rate law as a function of the viscosity of the medium and a diffusion parameter.

In the present w o r k , we have utilized 3 S C to study the thermal oxidation of four samples of mexican fuel oil. We have also obtained kinetic parameters such as the overall activation energy for the oxidation of the fuel at low temperature (200 - 55OOC).

EXPERIMENTAL

The experimentation was carried out by means of a DuPont Thermal Analyzer Model 990 with its standardDSC attachment. The instrument was calibrated with Indium. The temoerature was varied from 20 to 55OOC with a scanning rate of 10°C/min. The sensitivities used were 20 and 50 mV/cm. The sample and reference pans were made of aluminum, and the sample weight was kept at around 2 mg. Four different samples of mexican fuel oil # 6 were analyzed, and the experiments were performed with a constant flow of nitrogen, oxygen or a mixture of both. The flow rates, and the 02/N2 ratios utilized

121

t h roughou t t h e e x p e r i m e n t s are shown i n Table 1.


Experiments w i t h p u r e n i t r o g e n f low d i d n o t show any endothermic r e a c t i o n , b u t a g r a d u a l d i s p l a c e m e n t from t h e base l i n e , e s p e c i a l l y above 300OC. T h i s d i s p l a c e m e n t i n d i c a t e s t h a t t h e e v a p o r a t i o n o f some compounds i n t h e f u e l h a s ocu r red . A

r e s i d u e was obse rved i n t h e sample pan a f t e r t h e run w a s comple ted . F i g u r e 1 shows a t y p i c a l thermogram o b t a i n e d w i t h pu re oxygen f low. T h i s thermogram es v e r y s i m i l a r t o t h o s e shown i n t h e l i t e r a t u r e for t a r s a n d s ( 2 ) , or h i g h a s p h a l t e n e c rude o i l (9), which may show t h e q u a l i t y or t h e c h a r a c t e r i s t i c s o f t h e f u e l . Indeed , t h e f u e l s t u d i e d h e r e h a s a > 10% a s p h a l t e n e c o n t e n t , and z 3% s u l f u r . I n f i g u r e 1, it i s obse rved a s m a l l exo the rmic r e a c t i o n zone (zone 1) a t - 3OO0C, and a larger zone (zone 2 ) , also exo the rmic , which starts a t - 400OC. S e v e r a l s m a l l peaks are shown a t t h e low t e m p e r a t u r e s i d e o f t h e second zone. I t i s a l s o obse rved a r a p i d f a l l - o f f o f t h e s i g n a l a f t e r t h e maximum has been r eached . A l l t h e sample w a s consumed d u r i n g t h e expe r imen t s w i t h h i g h oxygen c o n c e n t r a t i o n i n t h e g a s flow. F i g u r e 2 , p r e s e n t s a thermogram o b t a i n e d w i t h a l o w oxygen c o n c e n t r a t i o n i n t h e gas flow. I t is

observed t h a t t h e r e a c t i o n zone i s s h i f t e d towards h i g h e r t empera tu res .

From t h e c a l i b r a t i o n of t h e i n s t r u m e n t w i t h I n , it was c a l c u l a t e d t h a t t h e s e n s i t i v i t y of 20 mV/cm cor responded t o 43.5 mcal/min-an. Tab le 2 shows t h e r e s u l t s fo r t h e h e a t o f r e a c t i o n measured f o r bo th exo the rmic zones i n t h e thermograms. The v a l u e s i n T a b l e 2 range from as h i g h a s 3.3 Kcal/g f o r t h e expe r imen t s w i t h p u r e 0 2 , t o as l o w as 1.4 Kcal/g f o r t h e expe r imen t s w i t h a 1 : 9 02/N2 ra t io . These v a l u e s f o r t h e h e a t of r e a c t i o n , are l o w

i f t h e y are compared w i t h t h e u s u a l h e a t c o n t e n t of t h e s e f u e l s , which i s .. 10 Kcal/g. O the r r e p o r t s (41, have also measured s imi la r h e a t s of r e a c t i o n t o t h o s e r e p o r t e d h e r e , and u t i l i z i n g a s imi l a r

1 2 2

t echn ique . The d i f f e r e n c e between o u r v a l u e s , and t h e v a l u e Of 10 Kcal/g f o r t h e h e a t c o n t e n t o f t h e f u e l are e x p l a i n e d as fo l lows: 1) F i r s t , w e have a f l o w sys t em i n which w e are c o n t i n u o u s l y c a r r y i n g away h e a t from t h e r e a c t i o n enve lope . 2 ) Second, most p r o b a b l y , w e do n o t have a complete o x i d a t i o n of t h e f u e l . That i s , w e do n o t have a comple te a d i a b a t i c combustion-type o f expe r imen t from which t h e h e a t c o n t e n t of t h e f u e l is normal ly e v a l u a t e d . I t must b e obse rved , t h a t t h e ex t reme v a l u e s f o r t h e h e a t o f r e a c t i o n i n t a b l e 2 w e r e o b t a i n e d for exoe r imen t s w i t h approx ima te ly t h e s a m e t o t a l f l ow. The o n l y d i f f e r e n c e among b o t h expe r imen t s i s t h e oxygen c o n c e n t r a t i o n . S i m i l a r f e a t u r e s w e r e obse rved i n o t h e r i n v e s t i g a t i o n s where TG and DTA w e r e used (2,9), and i n which t h e p r e s s u r e o f a i r i n s i d e t h e r e a c t i o n device w a s v a r i e d . That i s , t h e a c t u a l oxygen c o n c e n t r a t i o n , and a v a i l a b i l i t y f o r t h e f u e l w a s ,varied. W e may conclude t h a t d i f f e r e n t r e a c t i o n channe l s a r e b e i n g fo l lowed a c c o r d i n g t o t h e oxygen c o n c e n t r a t i o n . Hence, d i f f e r e n t h e a t s of r e a c t i o n are measured f o r t h e expe r imen t s w i t h p u r e 02, and f o r expe r imen t s w i t h a 1 : 9 O2/N2 ra t io .

I n o r d e r t o o b t a i n k i n e t i c s pa rame te r s from the

thermograms, w e u t i l i z e d t h e t h e o r y o f Borcha rd t and D a n i e l s (10). The zones I and I1 i n t h e thermograms w e r e t r e a t e d indepefl d e n t l y , and it w a s assumed a r e a c t i o n o f p s e u d o - f i r s t order. A

p s e u d o - f i r s t o r d e r k i n e t i c s i m p l i e s a f i r s t order r e a c t i o n w i t h r e s p e c t t o t h e f u e l , and a c o n s t a n t oxygen c o n c e n t r a t i o n . The

la t te r assumpt ion i s c l e a r l y j u s t i f i e d f o r t h e e x p e r i m e n t s w i t h

a h i g h oxygen c o n t e n t i n t h e g a s flow. A f i r s t o r d e r r e a c t i o n w i t h respect t o t h e f u e l may b e j u s t i f i e d th rough the r e s u l t s . F i g u r e 3 and 4 show t h e Ar rhen ius p l o t for t h e zone I o f the thermograms. The r e s u l t s i n f i g u r e 3 a r e f o r t h e e x p e r i m e n t s w i t h pu re oxygen; whereas t h o s e i n f i g u r e 4 p r e s e n t the e x p e r i m e n t s w i t h low c o n c e n t r a t i o n s o f 02 i n t h e g a s f low. For t h e d a t a i n f i g u r e 3 it i s p o s s i b l e t o draw t w o d i f f e r e n t s t r a i g h t l i n e s . Thus, t w o d i f f e r e n t a c t i v a t i o n e n e r g i e s a r e o b t a i n e d , one of 1251 Kcal/mol, and a h i g h e r one o f 222 1 Kcal/mol. From t h e d a t a

123

i n f i g u r e 4 , o n l y one a c t i v a t i o n energy h a s been o b t a i n e d w i t h a v a l u e o f 1621 K c a l / m o l . The lower v a l u e f o r E a i n t h e e x p e r i - ments w i t h p u r e O2 o c c u r s a t t h e h i g h e r t e m p e r a t u r e s o f zone I i n t h e thermograms. Thus, it i s p o s s i b l e t h a t d i f f u s i o n c o n t r o l l e d r e a c t i o n s o c c u r a t these t empera tu res . I n f a c t , it has been found

( 8 ) t h a t , the t h e r m o l y s i s of pe t ro l eum r e s i d u e s i n a TG e x p e r i - ment i s h i g h l y i n f l u e n c e d by d i f f u s i o n p r o c e s s e s . The r e s u l t s i n f i g u r e 4 , a l o n g w i t h t h e r e s u l t s o f t h e h e a t o f r e a c t i o n f o r the expe r imen t s w i t h a poor oxygen c o n c e n t r a t i o n , i n d i c a t e t h a t a d i f f e r e n t r e a c t i o n scheme i s b e i n g fo l lowed. T h i s l a s t statment s h o u l d be s u p p o r t e d by t h e i d e n t i f i c a t i o n o f t h e r e a c t i o n p r o d u c t s .

F i g u r e s 5 and 6 show t h e r e s u l t s f o r zone I1 i n t h e thermograms. F i g u r e 5 p r e s e n t s t h e r e s u l t s f o r t h e p u r e 0 2 e x p e r i - ments , and f i g u r e 6 p r e s e n t s t h e d a t a f o r t h e expe r imen t s w i t h a l o w oxygen c o n c e n t r a t i o n . I n t h i s case, w e on ly o b t a i n one a c t i v a t i o n e n e r g y f o r t h e p u r e oxygen d a t a ( f i g u r e 5) Ea=36+1 Kcal/mol. I n f i g u r e 6 w e o b s e r v e a s t r a i g h t l i n e o n l y f o r the

expe r imen t s w i t h a 1 :3 0 2 / N 2 r a t i o , and g a s f lows o f 4 1 ml/min and 87 ml/min. The rest o f t h e data p o i n t s i n f i g u r e 6 show large d e v i a t i o n s from a s t r a i g h t l i n e . These d e v i a t i o n s i n t h e e x p e r i - ments, w i t h the l o w e s t oxy gen c o n c e n t r a t i o n i n t h e g a s f l o w , s e e m t o i n d i c a t e t h a t w e may no l o n g e r assume a p s e u d o - f i r s t o r d e r k i n e t i c s .

The v a r i o u s t e c h n i q u e s i n t h e r m a l a n a l y s i s , may be v e r y

u s e f u l t o o b t a i n a n o v e r a l l v i e w o f t h e o x i d a t i o n r e a c t i o n s for mix tu res as complex as t h e heavy f u e l o i l . T h i s overal l p i c t u r e , may i n c l u d e q u a n t i t a t i v e i n f o r m a t i o n such a s a c t i v a t i o n e n e r g i e s .

I n g e n e r a l , w e believe t h a t t h e s e s t u d i e s may serve as a b a s i s to u n d e r s t a n d more complex o x i d a t i o n r e a c t i o n s such a s t h o s e o c c u r i n g w i t h i n a f lame.

ACKNOWLEDGMENTS

T h i s work is a r e s u l t o f t h e p r o j e t FE-F-lI/N o f t h e I n s t i t u t o de I n v e s t i g a c i o n e s Electricas.

124

REFERENCES

1) I. Glassman, "The Homogeneous Oxidation Kinetics of Hydrocarbons: Concisely and With Application", Annual Meeting of The Combustion Institute. Sezione Italiana, Torino, June 19.79.

2 ) L. Weber, "Application of DTA to Petroleum Chemistry", Chem. Inst. Can.,Proc. 1st. Toronto Symp. on Thermal Analysis, Feb. 8 1965, p.141-62.

3) 2. Adonyi , "Thermoanalysis of Petroleum products criticism to the Conradson number and a possibility to determine the flash point", Period Polytech, Chem. Eng. v 16 n 3 , 1972, p. 285-298.

4 ) F. Noel and G.E. Cranton, Anal. Calorimetry, 2, 305 (1974). 5) R.L. Blaine, American Laboratory, January 1974, 18. 6) E.J. Gallegos, "Analysis of Five U.S. Coals", Adv. in Chem.

Ser., No. 170, p. 13 (1979). 7) S.E. Smith, R.C. Neavel, R.N. Miller and E.J. Hippo, "DTGA

Combustion of Coals in the Exxon Coal Library", The Combustion Institute, Spring Meeting, Central States Section, Baton Rouge, March 1980.

8) G.G. Valayavin. V.V. Fryazinov, M. Yu. Dolomatov, and E.V. Artamonova, Khim. Tekh. Toplivi Masel, March 1980, p. 5 4 .

9) J.H. Bae, SOC. Petr. Eng. J.,/June 1977, p.211. 10) H.J. Borchardt and F. Daniels, J.Phys.Chem., 61, 917(1957).

125

TABLE 2

SAMPLE

#1 #2 #3 #4 #4 #4 #4 #4 #4

HEAT OF REACTION

FLOW RAT1 0

( m l / m i n ) 02:N2

90 90 90 98 89 87 9 1 4 1 24

l : o l : o l : o l : o 1: 1 1:3 1:9 1:3 1:3

ZONE I

(Kcal/g)

o 1 4 0.6 0,5 a,5 0,3 082 0,2 0,3 0.2

ZONE I 1

(Kcal/g)

1.9 2,5 2.5 2,7 1.8 1.6 112 1,6 1.4

1 2 6

TABLE 1

EXPER I MENTAL FLOW COND I T IONS

FLOW GAS RAT IO

90-100 90-100 85-90 85-90 40 24 11 90

0: 1 l : o 1:1 1:3 1:3 1: 3 1:3 1:9

127

Figure 1. Sample #4. Atmosphere: pure oxygen. Total flux: 98 ml/min.

MV

400

300

200

l oo-

-

-

-

+-pa----4 ?

I I I I I I 200 250 300 350 400 450 500 550

1

F i g u r e 2 . S a m p l e # 4 . A t m o s p h e , r e : 0 2 / N 2 (1:g). T o t a l f l u x : 9 1 ml/min.

128

d

5 Y

- +I cr,

19

- - N

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INVESTIGATION I N THE U S E OF HEAVY OILS (AN0 DERIVATIVES) TO PROCESS COAL

SpEROS E. HOSCHOPEDISI, RANDALL W . HAi.4KlNS1 2nd JAMES G. SPEIGHT’

1 . Coal Research Department A l b e r t a Research Counc i l

.I1315 - 8 7 t h Avenue Edmonton, A l b e r t a , Canada T5G 2C2

2 . Corpora te Research Science L a b o r a t o r i e s Exxon Research and E n g i n e e r i n g Company P.O. Box 45, L inden , N . S . 07036

I NTRODUCTI ON

The use o f o i l as an energy sou rce s t a r t e d f r o m t h e b e g i n n i n g o f t h i s c e n t u r y , and f o r many yea rs has been rega rded as t h e cheapest sou rce o f l i q u i d f u e l s . However, t h e r e c e n t d r a m a t i c e s c a l a t i o n i n work o i l consumpt ion and p r i c e , and t h e concern o v e r f u t u r e s u p p l i e s , wh ich a r e expec ted t o f a l l s h o r t o f demand by t h e end o f t h i s c e n t u r y , have f o r c e d t h e energy i n d u s t r y t o c o n s i d e r o t h e r sources f o r t h e p r o d u c t i o n o f l i q u i d f u e l s . The sources wh ich can p r o v i d e l i q u i d f u e l s a r e coa l and l i g n i t e , o i l sands, o i l s h a l e s , pea t , and biomass.

v e r t e d t o l i q u i d f u e l s , b u t r e q u i r e s enormous amounts o f expens ive hydrogen. I n a n a t t e m p t t o reduce t h e c o s t o f hydrogen r e q u i r e d t o c o n v e r t coa l t o l i q u i d f u e l s , t h e use o f o i l sands b i tumens , L l o y d m i n s t e r heavy o i l , and o t h e r l i q u i d s d e r i v e d t h e r e f r o m , have been r e p o r t e d ( 1 , Z ) as p o t e n t i a l l o w c o s t hydrogen donor s o l v e n t s . The p r e s e n t s tudy i s a c o n t i n u a t i o n o f t h e work r e p o r t e d e lsewhere (1,2) and r e p o r t s t h e e f f e c t o f process parameters ( i . e . t empera tu re , p ressu re and t ime) on t h e e x t e n t o f t h e c o a l c o n v e r s i o n and on p r o d u c t d i s - t r i b u t i o n .

\ Coal i s t h e l a r g e s t sou rce o f hydrocarbons i n t h e w o r l d w h i c h can be con-

EXPERIMENTAL ___-

O i l sands b i tumen ( d r y ) and coke r gas o i l were o b t a i n e d from Great Canadian O i l Sands L t d . (GCOS)’.. Cold Lake b i tumen and L l o y d m i n s t e r heavy o i l were o b t a i n e d from t h e A l b e r t a Research Counc i l sample bank. A l l samples were used as r e c e i v e d .

o f c o a l , and t h e p rocedure fo r t h e f r a c t i o n a t i o n o f t h e b i tumen and v a r i o u s l i q u i d d e r i v a t i v e s a r e d e s c r i b e d e l sewhere ( 2 , 3 ) .

o f t h e A l b e r t a Research Counc i l and t h e U n i v e r s i t y o f A l b e r t a . M o l e c u l a r we igh ts were measured o s m o t i c a l l y i n p y r i d i n e , and t h e nmr s p e c t r a were reco rded (carbon t e t r a c h l o r i d e s o l u t i o n s ) by means o f a V a r i a n E-60B spec t romete r . a n a l y s i s were o b t a i n e d by means o f a H e w l e t t Packard gas chromatograph f i t t e d w i t h a PoroDak N column and a m o l e c u l a r s i e v e .

The e x p e r i m e n t a l c o n d i t i o n s f o r t h e s o l v a t i o n and c a t a l y t i c h y d r o g e n a t i o n

Elementa l compos i t i ons were de te rm ined by t h e m i c r o - a n a l y s i s l a b o r a t o r i e s I Gas

* Now Suncor, O i l Sands D i v i s i o n . 131

The a r o m a t i c s c o n t e n t , f a , o f t h e b i tumen and d e r i v e d l i q u i d s has been d e f i n e d e lsewhere ( 2 ) .

RESULTS AN[! D I S C U S S I ON

The c u r r e n t communica t ion i s a c o n t i n u a t i o n o f t h e p r e v i o u s i n v e s t i g a t i o n s (1,2) whereby c o a l can be c o n v e r t e d t o s o l u b l e p r o d u c t s u s i n g o i l sands b i t u m e n , L l o y d m i n s t e r heavy o i l and l i q u i d s d e r i v e d t h e r e f r o m as s o l v e n t s .

The d a t a ( F i g u r e I ) i n d i c a t e t h a t i t i s , indeed, p o s s i b l e t o s o l u b i l i z e p a r t o f the c o a l by u s i n g t h e Athabasca b i t u m e n , and r e l a t e d l i q u i d s as s o l v e n t s , and as p r e v i o u s l y r e p o r t e d ( 1 , 2 ) t h e e x t e n t o f s o l u b i l i z a t i o n v a r i e s depending upon t h e t y p e o f s o l v e n t used. N e v e r t h e l e s s c o n v e r s i o n y i e l d s u s i n g these s o l v e n t s compared f a v o r a b l y t o t h e r e s u l t s o b t a i n e d when t e t r a l i n ( a w e l l - k n o w n hydrogen donor f o r c o a l l i q u e f a c t i o n ) was used as a s o l v e n t , p a r t i c u l a r l y i n t h e presence o f hydrogen. I t i s n o t e w o r t h y t h a t when t e t r a l i n was used as s o l v e n t , coa l c o n v e r s i o n y i e l d s f rom t h e s o l v a t i o n and n o n c a t a l y t i c and c a t a l y t i c hydro- g e n a t i o n show l i t t l e v a r i a t i o n ( i . e . f r o m 47-502) and p r a c t i c a l l y remain c o n s t a n t On t h e o t h e r hand, t h e p e r c e n t c o n v e r s i o n y i e l d s o f t h e o t h e r s o l v e n t s have shown a s u b s t a n t i a l i n c r e a s e i n t h e presence o f hydrogen, f o r example, f r o m IO t o 24% i n c o a l s o l v a t i o n t o 30 t o 4 0 % i n the c a t a l y t i c h y d r o g e n a t i o n ( F i g u r e I ) .

CONTROL E X P E R l MENTS

C o n t r o l e x p e r i m e n t s were per fo rmed i n t h e manner d e s c r i b e d e lsewhere (21, i n o r d e r t o d e t e r m i n e t h e degree o f coke ( to luene i n s o l u b l e s ) f o r m a t i o n d u r i n g t h e thermal t r e a t m e n t of t h e s o l v e n t s . B r i e f l y , when t h e s e l i q u i d s a r e heated w i t h o r w i t h o u t hydrogen ( i n t h e absence o f c a t a l y s t ) f o r 60 m i n u t e s a t 4 O O 0 C , an o v e r a l l i n c r e a s e i n t h e a r o m a t i c c o n t e n t s i s e v i d e n t as t h e i r H / C a t o m i c r a t i o s decrease and t h e i r f v a l u e s i n c r e a s e when compared w i t h t h e p a r e n t s o l v e n t s ( T a b l e I ) . I n c o n f r a s t , when t h e s o l v e n t s a r e heated i n t h e presences of hydrogen and c a t a l y s t , an o v e r a l l i n c r e a s e i n t h e a l i p h a t i c c o n t e n t i s e v i d e n t . The A P I g r a v i t i e s o f t h e s o l v e n t s a r e g e n e r a l l y i n c r e a s e d by t h e h e a t t r e a t m e n t b u t s u r p r i s i n g l y t h e A P I g r a v i t i e s o f CGOS b i t u m e n and coker gas o i l a r e d r a s t i c a l l y reduced ( T a b l e 2) when t h e s e s o l v e n t s a r e heated a t 450°C, a l t h o u g h l i q u i d p r o d u c t s o f h i g h f l u i d i t y were o b t a i n e d . I n a d d i t i o n , changes i n t h e h e t e r o - a t o m c o n t e n t s i n t h e s e s o l v e n t s ( T a b l e 1 ) . F o r example oxygen and s u l p h u r c o n t e n t s a r e decreased, p a r t i c u l a r l y d u r i n g t h e c a t a l y t i c hydro- g e n a t i o n o f t h e s o l v e n t , w h i l e n i t r o g e n c o n t e n t s i n genera l remained unchanged o r i n c r e a s e d s u p p o r t i n g t h e concept o f thermal s t a b i l i t y due t o i t s i n c l u s i o n i n h e t e r o - a r o m a t i c systems ( 4 ) . Compos i t iona l d i f f e r e n c e s o f t h e s o l v e n t s as a r e s u l t o f heat t r e a t m e n t a l s o o c c u r ( T a b l e 2) and t h e r e a r e v a r i a t i o n s i n t h e d i s t r i b u t i o n o f p r o d u c t s - - c o k e ( t o l u e n e i n s o l u b l e s ) , l i q u i d s ( t o l u e n e s o l u b l e s ) , and gases ( T a b l e 3 ) . Coke f o r m a t i o n under these c o n d i t i o n s (temp- e r a t u r e 400°C and 450°C) was a n t i c i p a t e d s i n c e o i l sands b i t u m e n and heavy o i l a r e s u s c e p t i b l e t o h e a t ( 5 , 6 ) . Compos i t ion o f gases f r o m t h e thermal t r e a t m e n t o f s o l v e n t s ( T a b l e 4) shows t h a t t h e gas p r o d u c t s m a i n l y c o n s i s t o f hydrocarbons and hydrogen s u l f i d e .

132

. ...

PROCESS CONDITIONS

EFFECT OF TEMPERATURE

a) Coal S o l v a t i o n

'Comparison o f t h e c o n v e r s i o n y i e l d s o f coa s o l v a t i o n , u s i n g GCOS b i tumen and coker gas o i l as s o l v e n t s ( T a b l e 5 ) , shows t h a t t h e c o n v e r s i o n y i e l d i s c o n s t a n t l y inc reased w i t h i n c r e a s i n g tempera tu e f o r c o a l / b i t u m e n p r o c e s s i n g w h i l s t t h e c o n v e r s i o n y i e l d reaches a maximum v a l u e a t 400"C, and t h e n d r a s t - i c a l l y d rops t o a lmost z e r o for c o a l / c o k e r gas o i l p r o c e s s i n g . Trends i n t h e d i s t r i b u t i o n o f t h e r e a c t i o n p r o d u c t s ( s o l i d s , l i q u i d s , and v o l a t i l e s , ( T a b l e 5) u s i n g t h e s e two s o l v e n t s were s i m i l a r .

The t o l u e n e i n s o l u b l e p r o d u c t s ( s o l i d s , u n d i s s o l v e d coa l p l u s coke) has a minimum v a l u e a t 400°C. w h i c h c o i n c i d e s w i t h t h e opt imum c o n d i t i o n s f o r t h e l i q u i d and v o l a t i l e p r o d u c t s , and t h e n d r a s t i c a l l y i n c r e a s e s a t 450°C due t o coke f o r m a t i o n as de termined f r o m b l a n k e x p e r i m e n t s ( T a b l e 3 ) . Because coke f o r m a t i o n o c c u r s s i m u l t a n e o u s l y w h i l e c o a l i s c o n v e r t e d t o l i q u i d and gaseous p r o d u c t s , g r e a t e r amounts o f t o l u e n e i n s o l u b l e s a r e o b t a i n e d t h a n t h e i n i t i a l coa l charge a t 450°C. Fur thermore , t h e l i q u i d ( t o l u e n e s o l u b l e s ) and v o l a t i l e p r o d u c t s f o l l o w o p p o s i t e p a t h s ; as the r e a c t i o n t e m p e r a t u r e i n c r e a s e s , t he maximum y i e l d o f v o l a t i l e s ( a t 450°C) cor respond t o t h e lowest y i e l d o f l i q u i d s , s u g g e s t i n g t h a t s o l i d s and v o l a t i l e s a r e produced a t t h e expense o f l i q u i d p r o d u c t s .

b) C a t a l y t i c Hydrogenat ion

i n c r e a s e o f r e a c t i o n tempera tures a r e s i m i l a r f o r b o t h s o l v e n t s w i t h t h e o n l y d i f f e r e n c e i n t h e y i e l d s o f s o l i d p r o d u c t s . Thus, t h e c o n v e r s i o n y i e l d s for b o t h s o l v e n t s a r e i n c r e a s e d w i t h t e m p e r a t u r e b u t when b i tumen i s used as solvent coa l c o n v e r s i o n y i e l d s reaches a maximum (a t about 400-450°C) w h i l e coa l c o n v e r s i o n y i e l d s w i t h coker gas o i l c o n t i n u e t o i n c r e a s e w i t h t e m p e r a t u r e .

w i t h the two types o f s o l v e n t s show ( T a b l e 5) t h a t t h e y i e l d s o f l i q u i d s a r e h i g h a t lower tempera tures ( i . e . , decrease w i t h i n c r e a s i n g t e m p e r a t u r e ) w h i l e t h e y i e l d s o f v o l a t i l e s i n c r e a s e w i t h i n c r e a s i n g tempera ture i n d i c a t i n g a g a i n , t h a t t he v o l a t i l e s a r e produced a t t h e expense o f l i q u i d p r o d u c t s . On t h e o t h e r hand, t h e y i e l d o f s o l i d s produced u s i n g coker gas o i l as s o l v e n t con- t i n u o u s l y decreases as tempera ture i n c r e a s e s ; t h e s o l i d s decrease and then appear t o i n c r e a s e as t h e tempera ture exceed 400°C.

EFFECT OF T I M E

a) Coal S o l v a t i o n

reaches a maximum v a l u e a f t e r 60 m i n u t e s a t 400"C, and t h e n d r a s t i c a l l y d rops . The p r o d u c t d i s t r i b u t i o n ( s o l i d s , l i q u i d s , and v o l a t i l e s ) i s s i m i l a r f o r b o t h t h e coker gas o i l and b i t u m e n and resembles t h e p r o d u c t d i s t r i b u t i o n f o r coa l s o l v a t i o n w i t h b o t h s o l v e n t s ( T a b l e 6 ) . I t i s apparent t h a t a r e a c t i o n t ime of 60 m i n u t e s a t 400°C c o i n c i d e s w i t h t h e opt imum c o n d i t i o n s f o r t h e m s t e f f i c i e n t p r o d u c t i o n o f l i q u i d p r o d u c t s .

I t i s apparent f rom t h e d a t a ( T a b l e 5) p resented t h a t t h e t r e n d s due to

The p e r c e n t d i s t r i b u t i o n o f t h e v a r i o u s p r o d u c t s d e r i v e d by p r o c e s s i n g coa l

The d a t a demonst ra te ( T a b l e 6) t h a t c o a l s o l v a t i o n y i e l d w i t h b o t h s o l v e n t s

133

b) C a t a l y t i c Hydrogena t ion

r e a c t i o n t ime , and then l e v e l s o f f , w h i l e w i t h coke r gas o i l c o n t i n u e s t o i n c - rease l i n e a r l y ( T a b l e 6 ) . The r e l a t i o n s h i p between t i m e and p r o d u c t d i s t r i b u t i o n by p r o c e s s i n g c o a l w i t h b i t umen show t h a t t h e r e i s n o t a d r a s t i c e f f e c t as t h e t i m e exceeds 60 m inu tes . However, when coke r gas o i l i s used as s o l v e n t , the l i q u i d p r o d u c t s a r e s t e a d i l y i nc reased and s o l i d s decrease w i t h o u t a s u b s t a n t i a l i n c r e a s e o f gases i n d i c a t i n g t h a t under t h e s e c o n d i t i o n s , l o n g e r p e r i o d s a r e b e n e f i c i a l .

Convers ion y i e l d s u s i n g b i tumen as s o l v e n t reach a maximum a f t e r 60 minutes

EFFECT OF PRESSURE

The l i m i t e d d a t a a v a i l a b l e (Tab le 7) show t h a t c o n v e r s i o n y i e l d s reach a maximum a t a p r e s s u r e o f a p p r o x i m a t e l y 1000 p s i g . There i s a pronounced e f f e c t on t h e y i e l d s o f l i q u i d p r o d u c t s wh ich a r e c o n s t a n t l y i nc reased w i t h i n c r e a s i n g p r e s s u r e ; v o l a t i l e s dec rease w i t h i n c r e a s i n g r e a c t i o n p r e s s u r e , w h i l e t h e r e i s a s m a l l v a r i a t i o n o f t h e s o l i d s a t p ressu re ove r 1000 p s i g .

Tables 8, 9, and IO show t h e r e l a t i v e c o m p o s i t i o n o f gases d e r i v e d f rom p r o c e s s i n g c o a l under v a r i o u s c o n d i t i o n s u s i n g b i tumen and coke r gas o i l as s o l v e n t s . A s p r e v i o u s l y d i scussed , t h e e v o l u t i o n o f oxygen and s u l p h u r f rom c o a l as carbon monoxide and d i o x i d e , and as hydrogen s u l p h i d e p a r t i c u l a r l y i n the c a t a l y t i c h y d r o g e n a t i o n o f coa l a r e t h e most n o t i c e a b l e f e a t u r e s .

ACKNOWLEDGEMENT

We thank Dr. M. P. du P l e s s i s f o r encouragement th roughou t t h i s work.

I .

2 .

3 .

4.

5.

6.

REFERENCES

Moschopedis, S . E . : "The use o f o i l sands b i tumen and i t s d e r i v a t i v e s as hydrogen donors t o c o a l " , F u e l , 59, 67, 1980.

Moschopedis, S . E . , Hawkins, R . W . , F r y e r , J . F . , and S p e i g h t , J .G. : "The use o f heavy o i l s (and d e r i v a t i v e s ) t o p rocess coa l " . F u e l , s, 647, 1980.

Moschopedis, S . E . , F r y e r , J .F. , and S p e i g h t , J . G . : " I n v e s t i g a t i o n o f t he ca rbony l f u n c t i o n s i n a r e s i n f r a c t i o n " . F u e l , s, 187, 1976.

Moschopedis, S . E . and S p e i g h t , J.G. " I n v e s t i g a t i o n o f n i t r o g e n t ypes i n Athabasca b i tumen". P r e p r i n t s , Am. Chem. S O C . , D i v . Fuel Chem., 4. ( 4 ) , 1007, 1979.

S p e i g h t , J.G. "Thermal c r a c k i n g o f Athabasca b i tumen , Athabasca aspha l tenes , and Athabasca d e a s p h a l t e d heavy o i l " , F u e l , 40, 134, 1970.

Spe igh t , J.C., and Moschopedis, S . E . , "The p r o d u c t i o n o f low-sulfur l i q u i d s and coke f rom Athabasca b i tumen", Fuel P r o c e s s i n g Technology 1, 295, 1979.

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135

f a b l e 2 . bitumen h e a t e d under v a r i o u s c o n d i t i o t s

Composi r ion and p r o p e r t i e s of bi tumens and l j g u l d s d r r i v r l f r r r

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GCOS b i t u m e n Athabas:a d e p o s i t

K O 5 c o k e r gas o i l

L l o y d e i n i s t e r heavy o i l

Cold Lake b i rvmen

Heated f o r 60 min a t boo' C. H, - 1000 p s i g + c a t a l y s t

- -~

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1 6 . 9 6G.5 1 . 5

2 0 . 1 6L.9 5 . 6

10.2 89 .6 16.0

13 .5 7L.O 1L.3

12 .0 73.5 11 .I

1 i . b a0.e 3.8*

1 1 . 9 70.9 3.6.

1 6 . 5 7b.8 11.1

1 0 . 3 89.5 21 .9

2?,0 6 6 . 1 1 6 . 8

12.2 76.6 . 12.9

1 2 . 1 79.5 12.5

7.9 92 .1 23.7

1 5 . 5 77.2 18.L

1 3 . 3 79.3 17.4

- 91.6 - 13.7 97.7 - 16.2

10.1 65.2 10 .3

7.0 93.0 20.6

136

I

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137

z8.n 6 9 . 8 1 . 4 16. I

2 8 . 0 6 9 . 1 2 . 6 19.5

2b. 1 6 5 . 1 8 . 5 19 .0

10.1 2 0 . 9 19 .0 1 5 . 3

27.1 7 1 . 9 I 0. 4 29.1 68.9 2 2.0

2 1 . b b8.2 8.2 3. 1

1 Y . 2 27.7 11.1 1.0

2b.2 10.7 1.1 11.0

22 .6 25.1 52.0 11.8

29.h 69.4 1 0 . 3 26.1 7 1 . 1 2 1.6

20. b 73.9 5 .5 1.11

I b . 3 12. 1 41.4 4 . 5

20.8 b9.1 10.1 12.5

rohv formed from che solurn1 in blank detcrmlnarlon..

0 . 9

MI. 5 81.0

81.7

99.6

98 .0

96 .9

97 .0

03.0 87.5

68.2

99.7

98.4

98 .2

95 .5

7.9

12.8

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k.4

11.1

15 - 18.9

8 . I

13.7

12.4

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17.4

11.0 11.1

8.5

2 b . l

2b.1

31.6

2b.8

21.6

25.6

2 4 . 2

20.8

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2 4 . 2

20.6

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65.4

51.3

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66.5

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5 . 3

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8.2

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6.6

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3.0

5 . 5

7 .1

21.7

1 9 . 0

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3.1

6.4

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11.5

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138

l d b l r 7. Prrnmure effect un e o ~ l cmver. lun yleldm and product d l s c r l b u l l o n (60 .Inute.. 400 i')

C.11.11ycic hydrogmdilon

WllS bitumen Alhabasc. deposlr

500 16 1 4 . 5 6 3 . 3 12 .2 1 7 . 8 82.2 9.6

1.000 31 2 0 . 1 69.1 10.1 1 2 . 5 77.5 12.b

1.500 30 1 1 . 7 68.3 10.0 1 5 . 0 85.0 11.b

2,000 30 2 1 . 8 75 .0 3 . 2 1 4 . 7 85.3 12 .1

to.1 .O l" . t lO"

GCOS bitswFn Iihabasc. dcposlr

3OO.C - 97.8 - - - 1.7

350'C 1.1 lL.5 3.6 10.5 - 5.9

400.c 0.6 31.9 7.5 31.6 - 1 5 . L

L S O ' C i n l v f f l c i c n t ..r.p1e

CCOS cokcr gas oil

300' c - 9L.O 1.5 - - 3.8

350.L. 1.6 6L.8 1 . 3 12.7 - lL.6

400.C N.D.

15O.C N.D.

C.t alut i c hydrogenat ion

1.4 55.1 10.3 12 .0 - 1 7 . 0

0.1 22 .8 24.4 26 .0 1 . 3 13.8

0 . 3 7 . 4 7.9 51.9 0.1 19.9

- - - 95.4 1.7 - 1.7 b2 .0 17.1 10.9 1.7 2.6

I.D.

0.1 b.1 b . 0 56.9 - 20.6

lot D8r.nln.d

139

0.5 - - 1 . 7 - 0.6

9.8 1.1 1 . 0

0.6 - - 2.9 0.1 0.9

3.5 - 0 . 9

8 .0 0.9 1 .9

9 . 1 0.9 1.9

0.9 - - 1.2 - 0.9

e.b 0.9 1.7

Tab:* 9 . Cas product dI.tribuCIon derlved from processing coal at 400 ' ' for

coal solvnrlon

CCOS b l n n m Athabamca d*pesIt

1 I L hour 1.0 4 L . l

1 hour 0 . 6 3 1 . 9

2 hours 2 . 0 3 7 . 1

CCOS coker I.' O i l

l / L hour 2 . 9 56.5

1 hour H.D.

2 hours 2 . 0 2 3 . 6

C.18lvfI~ h v d r o p n a r l o n GCOS bltumer. AlhabaLCa dcPosIt

111 hour 0.2 1 1 . 0

1 hour 0.7 2 2 . 0

2 hours 1.5 2 3 . 7

CCOS Coke* R.* Oil

114 hour 4.4 44.4

1 hovr N . D .

2 hours 2.6 Z 3 . 5

9 . 9 2 L . O - 1.5 31.6 -

13.7 2 L . 2 -

1.1 1 9 . 8 -

3 . L 39.2 0.1

19 .5 21.6 0.4

2L .L 2 6 . 0 1 . 3

10.i. 3 2 . 1 -

15.6 22.0 -

11.1 3L.9 -

9.6

1 5 . L

10.5

10.1

15.7

13.6

1 3 . 0

12.0

1 . 2

12.0

- 1 . 9 0.1 2.1

- 9 . 0 1.1 2.0

- 8 .0 1.0 2 . 1

- 6.2 0.1 1.1

- 16.6 2 . 1 2.9

- 0 . 0 0.9 1 . 9

- 8.5 1.3 2 . 3

- 5 . 0 0.3 1.0

- 7 . 1 0.1 1.5

Table I O . Car product d I s l r l b u c I o n dcrlved Iron p r o c c s r l n g coal for 60 mi". a1 4oo'c under V.li0". P*I.."I**

1 Relative composltlon Pre.s"rc P S l & CO C02 H25 CHI t2HL '2"b '2'2 '3 ,:$ krp C a t a l v r i c hvdroeenarion

CCOS bitumen Athabasc. d g o r l r

500 0 . 9 1 3 . 7 17.6 26.1 - 10.1 - 0.1 1 . 1 1 .3

1.000 0 .1 22.0 l L . 4 26.0 1 .3 11.0 - 8.0 0 . 9 1 .9

I. 500 1.5 26.2 2 2 . L 16.9 - 10.2 - 7.1 1.0 2 . 1

2.000 1.2 21.9 21.6 31.5 - 11.1 - 7 . 6 0 . 9 0.3

140

TECHNICAL RISK AS A COST FACTOR IN COAL LIQUEFACTION: SOME FINANCIAL CONSIDERATIONS

David A. Tillman

Senior Fuel Scientist Envirosphere Co.

Bellevue , Washington

INTRODUCTION

The U. S. economy is fueled largely by liquid fuels obtained, in no small measure, from unstable sources. The litany of wars, embargoes, and sudden price hikes implies that developing alternative indigenous supplies of liquid fuel is a national economic security issue. Liquid fuels derived from coal are among the alternatives available.

Coal liquids must replace petroleum products in existing applications when they enter the marketplace. That point of entry is almost unique [l-31. Coal liquids must replace oil directly, for domestic oil supplies are declining. This is also unique in the energy supply history of this country [ 4 - 5 1 . Thus the entry of coal liquids into the economy is fraught with uncertainties caused by unusual conditions.

Uncertainties in the marketplace exist; however a technical base for the development of a coal liquids industry has been developed. Generically four approaches have been pursued: pyrolysis, solvent extraction, catalytic hydrogenation, and indirect liquefaction. Of these, indirect liquefaction is being practiced commercially in countries outside the United States [ 6 ] .

The existence of a technical base does not imply that coal liquefaction is a mature technology. Rather, it shows that there is a significant gap between what is technologically available and what is economically available. This gap can be attributed to the efficiencies, the capital costs, and the financial risks of such systems. Those financial risks are substantially influenced by the magnitude of the investments and the status of the technology.

This financial gap has not always been recognized in the literature. In order to show the influence of this risk-related issue on coal liquefaction costs and market potentials, the following

141

c o n s i d e r a t i o n s are a d d r e s s e d h e r e : (1) a review of p r e v i o u s c o s t e s t i m a t i n g p r a c t i c e s , ( 2 ) an e v a l u a t i o n o f U.S. investment p r a c t i c e re la ted t o i n n o v a t i v e p r o c e s s e s , and (3) t h e i n f l u e n c e of t h o s e f a c t o r s on t h e c o s t s o f c o a l l i q u i d s .

In 1976 a major c o a l l i q u i d s economics symposium w a s h e l d by the American Chemical S o c i e t y . I n t h i s symposium a common se t of economic assumptions w e r e employed. The 1976 ACS symposium, and the values i n Table 1 used i n t h a t meet ing , r e p r e s e n t s a major s t e p i n uni fy ing c o a l l i q u e f a c t i o n economics. However t h e s e assumptions do n o t l e a d t o a s o l i d f i n a n c i a l a n a l y s i s of c o a l l i q u e f a c t i o n p l a n t s , and f o r t h e f o l l o w i n g r e a s o n s : t o f inance" w i t h "how t o f inance ' ' d e c i s i o n s ; ( 2 ) they mask t h e f a c t t h a t cash f low, n o t p r o f i t , s u p p o r t s a c o r p o r a t i o n ; and (3) t h e y do n o t i n c o r p o r a t e t h e i n f l u e n c e of t e c h n i c a l r i s k i n t o t h e d i s c o u n t rate.

(1) t h e y i n t e r t w i n e t h e ''what

The f i r s t d e f e c t a rgues that c o r p o r a t i o n s w i l l view new technologies w i t h t h e s a m e inves tment ground r u l e s as e x i s t i n g technolo- g i e s . Corpora t ions are r i s k a v e r s e , however, and p r e f e r t o i n v e s t i n improved e x i s t i n g sys tems r a t h e r than h i g h e r r i s k new systems [ 8 ] . Higher rates of d i s c o u n t are r e q u i r e d t o a t t r ac t c a p i t a l i n t o new p r o j e c t s . The second and t h i r d d e f i c i e n c i e s a r e v i o l a t i o n s of t h e p r i n c i p l e s of f i n a n c i a l a n a l y s i s [ l o ] . The u s e of any o r a l l of t h e s e t h r e e assumptions l e a d s t o o v e r l y o p t i m i s t i c product c o s t v a l u e s .

Given t h e s e problems, i t is u s e f u l t o reexamine t h e d i s c o u n t rate used i n c a l c u l a t i n g c o a l l i q u i d c o s t s , a d j u s t t h e account ing procedures t o s e p a r a t e "what t o f inance" from "how t o f i n a n c e , " and a n a l y z e c o s t s i n a way t o maximize cash f low. With t h e s e ad jus tments , o r d e r of magnitude p r i c e estimates may be made and, more i m p o r t a n t l y , t h e i n f l u e n c e s of r i s k and e x p e r i e n c e on product c o s t s can b e made.

THE DISCOUNT RATE AND COAL L I Q U I D COSTS

The nominal d i s c o u n t rate is composed of t h r e e e lements as shown i n formula (1):

Where I = t h e i n f l a t i o n rate, M = t h e r i s k l e s s c o s t of money (some- t i m e s r e f e r r e d t o as t h e premium f o r e a r l y a v a i l a b i l i t y of f u n d s ) , and R = t h e premium f o r t o t a l investment r i s k [ l o ] . Risk can be broken down f u r t h e r i n t o several components as shown i n formula ( 2 ) :

Where Re = economic r i s k ( e . g . , t h e r i s k of a r e c e s s i o n ) , R,, = b u s i n e s s

142

r i s k , Rf = f i n a n c i a l r i s k ( e . g . , degree of l e v e r a g e ) and R t = t e c h n o l o g i c a l r i s k . For most f i r m s , t h e Re term is u n c o n t r o l l a b l e and i s n o t i s o l a t e d . major innovat ion i s contempla ted , where t h e major i n n o v a t i o n w i l l i n f l u e n c e t h e c a p i t a l s t r u c t u r e .

Rt i s u s u a l l y subsumed i n b u s i n e s s r i s k i f no

C a l c u l a t i n g t h e Discount Rate

Each major i n d u s t r y h a s i ts own a p p r o p r i a t e nominal d i s c o u n t ra te r e f l e c t i n g t h e f i n a n c i a l inves tments of debt and e q u i t y par- t i c i p a n t s i n t h a t i n d u s t r y . While s e v e r a l models e x i s t f o r ca lcu- l a t i n g t h e d i s c o u n t rate, t h e Modiglani-Mil ler (M-M) theorem i s s u f f i c i e n t f o r t h e s e purposes . The model i s shown i n e q u a t i o n ( 3 ) from Haley and S c h a l l [ll].

DR = OKd + ( 1 - e ) Ke ( 3 )

Where 0 = t h e p r o p o r t i o n of d e b t , Kd = t h e c o s t of debt ( i n c l u d i n g t a x e f f e c t s ) and Ke = t h e c o s t of e q u i t y c a p i t a l . t h e y ie ld- to-matur i ty on bonds m u l t i p l i e d by 1-TR where TR = t h e Tax Rate, f r a c t i o n a l b a s i s . n iques vary ing i n s o p h i s t i c a t i o n . Again, due t o t h e i m p r e c i s e n a t u r e of d i scount ra te e s t i m a t i o n i n t h e f a c e of t e c h n o l o g i c a l r i s k , t h e s i m p l i s t i c approach i s taken h e r e and shown i n formula

Kd is t a k e n a s

Ke can be c a l c u l a t e d by s e v e r a l tech-

( 4 ) .

Ke = DIP + G ( 4 )

Where D = expected d i v i d e n d s , P = s t o c k p r i c e , and G = t h e expec ted growth r a t e o f t h e ( s t o c k ) investment over i t s u s e f u l l i f e .

The M-M model a p p l i e s t o t r a d i t i o n a l inves tments and i s based upon t h e p r i n c i p l e t h a t , w h i l e i n c r e a s i n g t h e d e b t f r a c t i o n d e c r e a s e s t h e apparent d i s c o u n t r a t e , i t i n c r e a s e s t h e d e g r e e of l e v e r a g e , t h e f i n a n c i a l r i s k and hence t h e c o s t of e q u i t y c a p i t a l . Based upon t h e above e q u a t i o n s , T a b l e s 2 and 3 are p r e s e n t e d , g i v i n g t h e e s t i m a t e d d i s c o u n t rates f o r Gul f , Exxon, and Mobil O i l . Growth estimates a r e based on 10-year e a r n i n g s l s h a r e r a t i o s . For subsequent a n a l y s i s , t h e nominal r a t e of 15% i s used s i n c e i t shows t h e approximate 1 :3 d e b t l e q u i t y r a t i o common t o t h e energy i n d u s t r y [ 1 2 ] and is t h e median c a s e c a l c u l a t e d .

Table 2 p r e s e n t s t h e c a p i t a l s t r u c t u r e f o r Exxon, G u l f , and Mobil--the t h r e e companies chosen t o develop t h e d i s c o u n t r a t e f o r t h i s i n d u s t r y . S i g n i f i c a n t i s t h e absence of p r e f e r r e d s t o c k i n t h e s e companies. Also s i g n i f i c a n t t o n o t e i s t h a t there is heavy r e l i a n c e on common s t o c k . Thus t h e growth i s s u e a r i s e s ; and i t i s

14 3

complicated by v a r y i n g e x p e c t a t i o n s concern ing t h e d e c o n t r o l of pe t ro leum p r i c e s .

The I n f l u e n c e of R i s k on t h e Discount Rate

The f i n a n c i a l l i t e r a t u r e i s r e p l e t e w i t h c i t a t i o n s concern ing t h e i n f l u e n c e of b u s i n e s s and f i n a n c i a l r i s k on t h e d i s c o u n t rate. The t y p i c a l r e l a t i o n s h i p shown is e s s e n t i a l l y l i n e a r and i s r e f e r r e d t o as t h e " S e c u r i t y Market Line" shown i n F ig . 1.

Technica l r i s k and/or u n c e r t a i n t y i s less w e l l - t r e a t e d i n t h e l i t e r a t u r e t h a n b u s i n e s f f i n a n c i a l r i s k . T e c h n i c a l r i s k , however, i s c r i t i c a l t o new energy inves tment e v a l u a t i o n [13] . Its i n f l u e n c e can b e e v a l u a t e d by analogy t o t r a d i t i o n a l b u s i n e s s / f i n a n c i a l r i s k assessments .

Empir ica l s t u d i e s have addressed t h e r isk i s s u e , i n c l u d i n g r e p o r t s b y t e c h n i c a l Micro Economic A s s o c i a t e s [ 1 4 ] and Robert R. Nathan A s s o c i a t e s [ 1 5 ] . The former d e a l s l a r g e l y w i t h t h e i n f l u e n c e of r i s k s on s u p p l i e s and p r i c e s ; and t h e l a t t e r shows rates of r e t u r n o b t a i n e d on i n n o v a t i o n s i n U.S. i n d u s t r y s i n c e 1940. Pre- t a x p r i v a t e i n t e r n a l ra tes of r e t u r n (IRR) ranged from n e g a t i v e t o 157% over a broad spec t rum i n n o v a t i o n s on a r e a l d o l l a r b a s i s .

Two petroleum i n d u s t r y i n n o v a t i o n s , one i n e x t r a c t i o n and one i n p r o c e s s i n g , showed pre- tax IRR v a l u e s of 50 t o 56% i n the Nathan A s s o c i a t e s s t u d y . T h i s is s l i g h t l y h i g h e r t h a n t h e median v a l u e of 34 t o 38%. Given s t a n d a r d economic assumpt ions , a f t e r t a x r a t e s of r e t u r n can be c a l c u l a t e d a t 1.20% on average and 2.30% i n t h e petroleum i n d u s t r y . It s h o u l d b e noted t h a t t h e pe t ro leum r e l a t e d inves tments were made i n 1942 and 1949. However, a mining r e l a t e d i n n o v a t i o n in t roduced i n 1964 had a p r e - t a x IRR of 54%. These I R R v a l u e s are n o t d i s c o u n t rates p e r se , b u t t h e y g i v e some c l u e t o i n v e s t o r e x p e c t a t i o n s . Thus, r e s o u r c e i n d u s t r y i n n o v a t i o n s may g e n e r a l l y r e q u i r e t h e h i g h e r d i s c o u n t rates.

The r i s k - a d j u s t e d d i s c o u n t ra te a l s o i s a f u n c t i o n o f some l e a r n i n g c u r v e c o n c e r n i n g t h e new technology. Those e x t r a c t i v e i n d u s t r y i n n o v a t i o n s which f i r s t earned %30% a f t e r t a x e s now r e q u i r e 1.15%. The i n i t i a l par ts of t h e inves tment l e a r n i n g c u r v e , b o t h tech- n i c a l l y and f i n a n c i a l l y , re la te t o t h e p r o c e s s of going from concept development and bench s c a l e r e s e a r c h t o commercial t e c h n o l o g i e s through p r o c e s s development u n i t s and t h e n p i l o t p l a n t s . Swabb [161 i d e n t i f i e s t h e p r e f e r r e d succeeding s t e p from p i l o t p l a n t t o commercial technology as a p i o n e e r p l a n t , t o b e owned and o p e r a t e d by t h e private i n d u s t r y as a commercial f a c i l i t y fol lowed by t h e d e s i g n and c o n s t r u c t i o n of succeeding commercial p l a n t s . The p i o n e e r p l a n t

144

is critical in this approach as it demonstrates plant reliability, product output, environmental protection safeguards, and commercial viability. It reduces business risk to manageable levels.

If one accepts the Schwabb argument, then the discount rate for the pioneer plant may be nominally %30%. The lower limit is, of course, nominally 15%. The upper limit, however, remains essentially undefined. Further, the number of commercial plants required to go from 30% to 15%, is also undefined.

Similar learning curves have been posited for capital cost estimates [17, 181. Such curves take the form of sensitivity analysis parameters. The analogy between capital cost and discount rate estimation is imperfect, both sets of data deal with investment uncertainties as perceived by boards of directors. Despite these uncertainties, a 30% discount rate is used here for pioneer plants, and a 15X discount rate is used for mature plants.

The empirical technical risk adjustment made here is analogous to an unusual business risk taken. Before the passage of the Public Utility Regulatory and Policies Act (PURPA), industries entering cogeneration ventures perceived the following risks: (1) would they be regulated as utilities; (2) would utilities purchase surplus power from them; and ( 3 ) would utilities sell them power as needed at a reasonable cost. Frequently after-tax rates of return demanded by cogenerators were 30% [19]. Again it is an imperfect analogy. The investment community is consistent--manufacturing industry. The broad investment arena is energy. The cogeneration technology, however, is mature. Thus this risk adjustment is only one more indi- cator of investor behavior.

CALCULATED COSTS OF COAL LIQUIDS UNDER UNUSUAL AND NORMAL RISK CONDITIONS

Remaining are the tasks of estimating the initial costs of coal liquids and the price reductions possible as investor corporations gain commercial experience in coal liquefaction. Accomplishing these evaluations requires making some accounting assumptions. It then involves calculating fuel costs based on the systems selected.

Accounting Conventions and Assumptions

In the projecting of synthetic fuel costs, certain conventions play an important role: (1) the selection of a depreciation method; and (2) the selection of a dollar basis.

145

Three d e p r e c i a t i o n methods exist: s t r a i g h t l i n e , sum-of-the y e a r s d i g i t s , and d o u b l e d e c l i n i n g b a l a n c e . In g e n e r a l , t h e l a t t e r two a c c e l e r a t e d sys tems g e n e r a t e more f a v o r a b l e cash f lows (depend- i n g upon t h e c a p i t a l s t r u c u t r e of the i n d u s t r y ) . The double d e c l i n i n g b a l a n c e method g e n e r a t e s p a r t i c u l a r l y h i g h d e p r e c i a t i o n v a l u e s i n t h e f i r s t f e w y e a r s . Thus, i t i s used here .

D e p r e c i a t i o n may b e t a k e n over a v a r i e t y of t i m e p e r i o d s . To maximize c a s h f low, and t h e c o n t r i b u t i o n of d e p r e c i a t i o n t o n e t p r e s e n t v a l u e , t h e s h o r t e s t p o s s i b l e d e p r e c i a t i o n p e r i o d i s p r e f e r r e d . The I n t e r n a l Revenue S e r v i c e [20] g i v e s a minimum of 1 3 y e a r s f o r pe t ro leum r e f i n e r i e s ; and t h i s v a l u e i s assumed t o hold f o r c o a l l i q u e f a c t i o n p l a n t s .

D e p r e c i a t i o n i s t h e major a r e a of c a p i t a l recovery m e r i t i n g documentat ion. t i o n s f o r c o s t i n c r e a s e s o v e r t i m e . These are shown i n Table 4 . These v a l u e s are used i n c o n s t r u c t i n g proforma s t a t e m e n t s .

H i s t o r i c a l s ta t is t ics can be used t o deve lop assump-

System and Product C o s t s

Two sys tems have been s e l e c t e d f o r a n a l y s i s h e r e : (1) methanol s y n t h e s i s and (2) s o l v e n t e x t r a c t i o n . Methanol i s advanced f r e q u e n t l y as a technology of immediate a p p l i c a t i o n [21, 221. Solvent ex t rac- t i o n i s c o n s i d e r e d one of the l e a d i n g c a n d i d a t e s f o r b o i l e r f u e l s p r o d u c t i o n [ 2 3 ] . S l i e p c e v i c h e t a l . 1 2 4 1 . Table 5 p r e s e n t s t h e s i g n i f i c a n t c a p i t a l c o s t and product o u t p u t parameters f o r each u n i t . The c o s t v a l u e s have been updated to 1980 d o l l a r s from the o r i g i n a l p u b l i c a t i o n by u s e of t h e chemical e n g i n e e r i n g p l a n t c o s t index as r e p o r t e d i n t h e Engineer ing News Record [25] .

Both systems are d e s c r i b e d g e n e r i c a l l y i n

Both t h e methanol and s o l v e n t e x t r a c t i o n p l a n t s w e r e e s t i m a t e d t o c o s t $ 1 x lo9 i n 1 9 7 7 , and a r e now e s t i m a t e d t o c o s t $1.3 x lo9. A f t e r removal of t h e 20% investment t a x c r e d i t , t h e s e c a p i t a l c o s t s are $1.04 x lo9. If one assumes a 13-year a m o r t i z a t i o n p e r i o d , the r i s k y inves tment w i t h a d i s c o u n t rate of 30% must g e n e r a t e an annual a f t e r - t a x cash f low of $322 x l o 6 . by i n v e s t o r s t o b e m a t u r e , t h a t a f t e r - t a x cash f low requi rement would be $178 x l o 6 . s i n c e inves tment t a x c r e d i t s and d e p r e c i a t i o n a r e c a l c u l a t e d w i t h o u t r e g a r d t o t e c h n o l o g i c a l matury. Thus t h e $144 x lo6 must b e made up e n t i r e l y w i t h a f t e r - t a x p r o f i t s .

I f t h e technology were cons idered

The d i f f e r e n t i a l is p a r t i c u l a r l y s i g n i f i c a n t

From t h e s e d a t a , modif ied proforma s t a t e m e n t s have been con- s t r u c t e d f o r b o t h t e c h n o l o g i e s assuming: (1) i n s t a n t a n e o u s cons- . s t r u c t i o n and s t a r t u p and (2) c o n s t a n t a f t e r - t a x cash f lows . These

,

146

I

are o p t i m i s t i c assumptions b u t they do n o t a f f e c t t h e a n a l y s i s of f i n a n c i a l r i s k r e d u c t i o n s e r i o u s l y , s i n c e t h e y are c o n s t a n t r e l a t i v e t o t h e v a r i a b l e d i s c o u n t rate. Table 6 is t h e proforma s t a t e m e n t f o r s e l e c t e d y e a r s of t h e r i s k y s o l v e n t e x t r a c t i o n p l a n t . i s t h e proforma statement f o r t h e same y e a r s assuming a mature technology. Values are i n nominal ( i n f l a t e d ) d o l l a r s .

Table 7

It i s s i g n i f i c a n t t o n o t e t h a t t h e h i g h r i s k p l a n t must b e p r o f i t a b l e from t h e s tar t . The mature p l a n t can s u s t a i n l o s s e s dur- i n g t h e f i r s t y e a r w i t h o u t j e o p a r d i z i n g t h e cash f low stream. Depre- c i a t i o n is f o r more s i g n i f i c a n t t o t h e mature p l a n t t h a n t h e h i g h r i s k p i o n e e r p l a n t . f o r methanol p l a n t s . Revenue streams can t h e n d e d e f l a t e d t o 1980 d o l l a r s by t h e f o l l o w i n g formula:

S i m i l a r proforma s t a t e m e n t s can b e c o n s t r u c t e d

t D t = 1.064

Where D = d e f l a t o r and t = t h e year of o p e r a t i o n . From t h e s e v a l u e s Table 8 i s c o n s t r u c t e d showing t h e approximate c o s t o f f u e l s from p i o n e e r p l a n t s and mature p l a n t s . I n b o t h cases t h e g a i n i n g o f f i n a n c i a l e x p e r i e n c e carries a c o s t s a v i n g s of about $ lO/bbl o f o i l e q u i v a l e n t .

What i s s i g n i f i c a n t h e r e i s n o t t h e $40/bbl o r $60/bbl v a l u e . These are b e s t g u e s s e s based upon a v a i l a b l e i n f o r m a t i o n from p i l o t p l a n t s . Nobody knows what c o a l l i q u i d s w i l l a c t u a l l y c o s t . Rather, i t i s t h e c o s t r e d u c t i o n a s s o c i a t e d w i t h i n v e s t o r e x p e r i e n c e which i s s i g n i f i c a n t . Cost s a v i n g s of $1-2/106 Btu are s u b s t a n t i a l . These r e s u l t from a r e d u c t i o n i n t h e d i s c o u n t ra te as r i s k s and u n c e r t a i n - t i e s are reduced.

CONCLUSION

S u b s t a n t i a l f u e l c o s t s a v i n g s , t h e n , are a v a i l a b l e from corpora- t i o n investment e x p e r i e n c e i n c o a l l i q u e f a c t i o n f a c i l i t i e s . These s a v i n g s are i n t h e v i c i n i t y of $ lO/bbl o r $1-2/106 Btu. i n g s a l s o should be pursued. b e achieved when i n v e s t o r s advance a long t h e i r own l e a r n i n g c u r v e . That l e a r n i n g c u r v e e q u a t e s t h e r e l a t i o n s h i p of expec ted product p r i c e and p l a n t performance t o achieved product p r i c e and p l a n t per - formance; and translates t h a t r e l a t i o n s h i p p l u s market a c c e p t a n c e o f t h e product i n t o a r i s k f a c t o r and a n a p p r o p r i a t e d i s c o u n t r a t e . Large s a v i n g s i n f u e l c o s t s can be achieved o n l y when i n v e s t o r s have advanced s u f f i c i e n t l y t o reduce t h e i r p e r c e p t i o n s of l i q u e f a c t i o n r i s k and u n c e r t a i n t y .

These sav- These s u b s t a n t i a l p r i c e r e d u c t i o n s may

147

REFERENCES

1. H o t t e l , H. C. and J. B. Howard. 1971. New Energy Technol- ogy: Some F a c t s and Assessments. MIT P r e s s , Cambridge, Mass.

2 . Frey , J. W . and H. C. I d e . 1946. A H i s t o r y o f t h e Petroleum A d m i n i s t r a t i o n f o r War: 1941-1945. U.S. Government P r i n t i n g O f f i c e , Washington, D.C.

3 . N a t i o n a l Materials Advisory Board. 1975. Problems and L e g i s l a t i v e O p p o r t u n i t i e s i n t h e Basic Materials I n d u s t r y . N a t i o n a l Academy of S c i e n c e s , Washington, D.C.

4 . T i l lman, D. A. 1978. Wood as an Energy Resource. Academic P r e s s , New York.

5. Enger , H . , W. Dupree, and S. Miller. 1975. Energy Perspec- t ives: d a t a . U.S. Department of t h e I n t e r i o r , Washington, D.C.

6. Smith, I. H. and G. J. Werner. 1976. Coal Conversion Tech-

A p r e s e n t a t i o n o f major energy and energy-re la ted

nology. Noyes Data Corp. , Park Ridge, N . J .

7 . P e l o f s k y , A. H. 1977. P r e f a c e , i n S y n t h e t i c F u e l s P r o c e s s i n g : Comparative Economics ( P e l o f s k y , A. H. e d . ) , Marcel Dekker, New York, i i i -v .

8. P e r r y , H . 1979. S y n t h e t i c F u e l s Commercial izat ion Testimony b e f o r e t h e House Committee on Sc ience and Technology, Sept . 12 .

9 . Bierman, H . , and S. Smidt. 1971. The C a p i t a l Budget ing Decis ion . Macmil lan, N e w York.

10. S c h a l l , L. D . , and C. W. Haley. 1977. I n t r o d u c t i o n t o Finan- c i a l Management. McGraw-Hill, New York.

11. Haley, C. W . , and L. D. S c h a l l . 1979. The Theory of F i n a n c i a l Decis ions . M c G r a w - H i l l , N e w York.

1 2 . Haas, J . E . , E . J. Mitchell, and B. K. Stone. 1974. Finan- cing t h e Energy I n d u s t r y . B a l l i n g e r , Cambridge, Mass.

13. Ti l lman, D. A. 1980. A f i n a n c i a l a n a l y s i s of s i l v i c u l t u r a l f u e l farms on margina l l a n d s . Ph.D. D i s s e r t a t i o n , Col lege of F o r e s t Resources , U n i v e r s i t y o f Washington, S e a t t l e , Wash.

148

14.

15.

16.

17.

18.

19.

20.

21.

22.

23.

24.

25.

Microeconomic Associates. 1978. Effect of Risk on Prices and Quantities of Energy Supplies. Electric Power Research Insti- tute, Palo Alto, Calif.

Robert R. Nathan Assoc. 1978. Net Rates of Return on Innova- tions: Final Report. Vol. 1. Technical Report. Washington, D.C. (for the National Science Foundation).

Swabb, L. E. 1978. Liquid Fuels from Coal: From R & D to an Industry. Science 199(4329), 619-622.

Adams, M. R., C. W. Knudsen, and C . W. Draffin. 1977. Econ- omic Evaluation by ERDA of Alternative Fossil Energy Technolo- gies, Synthetic Fuels Processing: Comparative Economics (Pelofsky, A. H., ed). Marcel Dekker, New York.

Beath, B. C. 1979. Guidelines for Economic Evaluation of Coal Conversion Processes. The Engineering Societies Commis- sion on Energy, Washington, D.C.

Stobaugh, R. and D. Yergin (eds.). 1979. Energy Future: Report of the Energy Project at the Harvard Business School. Random House, New York.

3 -

for

Anon. 1980. Builders'construction cost indexes. Engineering News Record 2O5(25) :77.

Internal Revenue Service. 1977. Tax Information on Deprecia- tion. Department of the Treasury, Washington, D.C.

Perry, H. 1978. Systems and Technologies, Vol. 1 (Auer, P., ed.), Academic Press, New York.

Clean fuels from coal, &I Advances in Energy

Stokes, C. A. 1979. Synthetic Fuels at the Crossroads Technology Review, Aug/Sept. 25-33.

Whitaker, R. (7) 6-13.

1978. Scaling up coal liquids. EPRI Journal

Sliepcevich, C. M. et al. 1977. Assessment of Technology the Liquefaction of Coal. Academy of Sciences, Washington, D.C.

National Research Council/National

149

Discount Rate (%)

40

30

20

10

I I I 1 2 3 4

Degree of Risk ( B )

F i g u r e 1. The d i s c o u n t r a t e , o r c o s t o f money, a s a f u n c t i o n of t h e d e g r e e of r i s k a s s o c i a t e d w i t h t h e inves tment . T h i s c u r v e i s known a s t h e S e c u r i t y Market Line .

150

TABLE 1. F i n a n c i a l Assumptions f o r t h e 1976 American Chemical S o c i e t y Meeting on S y n t h e t i c Fue l Economics

Parameter Value

P r o j e c t l i f e 20 y e a r s Cost of c a p i t a l 10 p e r c e n t Deprec ia t ion S t r a i g h t l i n e Base Return on Investment 15 p e r c e n t a

aNot s p e c i f i e d bu t r e q u e n t l y used. Source: [ 7 ]

TABLE 2 . The C a p i t a l S t r u c t u r e of Three Petroleum Companies, 1979

Company

Cap i t a l Instrument Gulf Exxon Mobil

Debt . 191 . 1 1 2 P r e f e r r e d s t o c k -0- -0- Common s t o c k .809 .888

.261 -0-

.739

T o t a l 1.00 1.00 1.00

TABLE 3. The Cost of C a p i t a l f o r Three Petroleum Companies ( i n %)

C a p i t a l Cost C o n t r i b u t i o n by Company

C a p i t a l Instrument Gulf Exxon Mobil

Debt p o r t i o n 0. 97a 0.54 Common e q u i t y p o r t i o n 11.6 16 .3 e 14.0

T o t a l 12.6 16.8 15.2

1.18' b

a .191 x .570 x .089 x 100 = 0.97; .089 = Yield t o Matu r i ty on

' .112 x .553 x .087 x 100 = 0.54; .087 = Yield t o Matu r i ty on

(Continued n e x t page.)

bonds

bonds.

1 5 1

.261 x .524 x .086 x 100 = 1.18; 0.86 = Y i e l d t o Matu r i ty o n bonds.

Second term i n a l l above c a l c u l a t i o n s = 1 - TR f o r domestic o p e r a t i o n s . Thus t h e t a x e f f e c t of i n t e r e s t i s accounted f o r i n t h e d i scoun t rate c a l c u l a t i o n .

d 2.05

30.75 + .076 = .143; .143 x .809 = .116

e + .112 = .183; .183 x .888 = .163

56 .5

2.40 42.625

+ .135 = .190; .190 x .739 = 14.0

De

fo l lows : 'e

KCeq w h e r e De = expec ted d iv idend , P = p r i c e , and Ge = expected growth and Kceq = c a p i t a l c o s t , common e q u i t y .

August, 1979; WSJ, August 28; Value Line.

General formula f o r d , e , f , is - + G = K as de f ined as

The c o s t o f common e q u i t y c a p i t a l i s determined by De/P + Ge =

ceq

Sources: Annual Repor t s , 1978; Standard and P o o r ' s Bond Guide,

TABLE 4. Real P r i c e I n c r e a s e s 1968-1978

1 0 Y r Nominal 1 0 Y r Real Good/ S e r v i c e Rate (%) Rate (%)

A l l goods and S e r v i c e s (CPI) 6 .4 - 0-

Labor U t i l i t i e s Chemical manufac tu r ing

Fue l s and Energy Coal E l e c t r i c i t y

Chemicals ( I n d u s t r i a l ) Miscel laneous s u p p l i e s

Supp l i e s

8 .4 2.0 8 . 3 1.9

1 1 . 7 5 . 3 9 .3 2.9

8 .3 1 . 9 6 .0 -0.4

S e r v i c e s 7 .0 0.6

Sources: U. S. Census Bureau, 1978; U.S. Census Bureau, 1974; U . S . Bureau of Labor S t a t i s t i c s , 1980.

152

TABLE 5. Cost and Output Parameters for Selected Solvent Extraction and Methanol Plants

Technology

Solvent Parameter extraction Me t h ano 1

Plant size 50 x lo3 bbljday 11,300 tonsiday

Thermal efficiency 64% 46%

325 x lo9 Btu/day 230 x lo9 Btuiday

1977 capital cost total $0.9 - 1.15 109 $0.85 - 1.2 109

Median 1980 capital cost (gross) $1.3 x lo9 $1.3 109

1977 capital costlbbllday $16.5 - 21.5 x lo3 $23 - 30 x lo3

1980 investment tax credit $260 x lo6 $260 x lo6

Source : [ 241 . TABLE 6. Pro Forma Statement for the Solvent Extraction Plant

30% Discount Rate (Values in $ x 106)

Year CostIIncome Stream 1 5 13

Revenue 655 988 1677 Operating cost Fuel 223 34 7 841 Labor 6 8 15 Chemicals and supplies 14 18 31 Water and utilities 2 2 3 Maintenance 68 94 17 7 Taxes and insurance 16 20 37

Depreciation 200 103 27 Earnings before taxes 226 406 54 6 Income tax (46%) 104 187 251 Net income after taxes 122 219 295 Depreciation 200 103 27 Cash flow 322 322 322

Sources: Table 5 and [24].

153

TABLE 7 . Pro Forma Sta tement f o r t h e Solvent E x t r a c t i o n P l a n t - 15% Discount R a t e (Values i n $ x l o 6 )

Year Cost/Income Stream 1 5 1 3

Revenue 507 731 1 4 1 1 Opera t ing c o s t

F u e l 2 2 3 347 841 Labor 6 8 1 5 Chemicals and s u p p l i e s 1 4 18 3 1 Water and u t i l i t i e s 2 2 3 Maintenance 68 94 1 7 7 Taxes and i n s u r a n c e 16 20 37

Deprec ia t ion 200 103 27 Earn ings b e f o r e t a x e s (22) 139 280 Income t a x (46%) - 0- 64 129 N e t income a f t e r t a x e s ( 2 2 ) 75 1 5 1 D e p r e c i a t i o n 200 103 27 Cash flow 178 1 7 8 178

Sources : T a b l e 5 and [ 2 4 ] .

TABLE 8. Leve l i zed F u e l Cos t s f o r P ionee r and Mature Coal Conversion P l a n t s ( i n 1980 D o l l a r s )

F u e l Cost

P ionee r P l a n t Mature P l a n t Coal L i q u e f a c t i o n System $ / I O 6 B t u $ / b b l $ / l o 6 B t u $ / b b l

Solvent e x t r a c t i o n a 50

Methanol 10 60

7 40

8 50

154

SYNTHETIC POLYMERS AS MODELS FOR COAL I N A DESULFURIZATION PROCESS

Thomas E. Schmidt , Thomas G . S q u i r e s and C l i f f o r d G . Venier

Ames Labora tory* , Iowa S t a t e U n i v e r s i t y , Ames, Iowa 50011

O x y d e s u l f u r i z a t i o n p r o c e s s e s u s e a i r o r oxygen t o remove s u l f u r from c o a l f o r t h e purpose o f c o n v e r t i n g h i g h s u l f u r c o a l i n t o a n e n v i r o n m e n t a l l y a c c e p t a b l e s o l i d f u e l (I). The d e s u l f u r i z a t i o n is main ly from t h e c o n v e r s i o n of p y r i t i c s u l f u r i n t o s u l f a t e and i t s removal when t h e c o a l i s recovered from t h e aqueous s l u r r y of t h e p r o c e s s ( 2 ) . Because e v i d e n c e f o r t h e removal o f o r g a n i c s u l f u r from c o a l could r e v i t a l i z e t h e now dormant s t a t u s of o x y d e s u l f u r i z a t i o n as a method o f c o a l b e n e f i - c i a t i o n , w e have been i n v e s t i g a t i n g t h e a b i l i t y of t h e s e p r o c e s s e s t o d e g r a d e or - g a n i c s u l f u r f u n c t i o n s .

A d i r e c t comparison of a c o a l ' s o r g a n i c s u l f u r c o n t e n t b e f o r e and a f t e r pro- c e s s t r e a t m e n t i s f r a u g h t w i t h u n c e r t a i n t y due t o t h e c o n f u s i o n i n d i s t i n g u i s h i n g t h e v a r i o u s forms of s u l f u r i n c o a l ( 3 ) . T h e r e f o r e , our e v a l u a t i o n o f t h e Ames P r o c e s s , which employs oxygen and 0.2 M aqueous sodium c a r b o n a t e a t 200 p s i t o t a l p r e s s u r e and 150° C , h a s been based on t h e u s e of model compounds ( 4 ) . In t h e s e i n v e s t i g a t i o n s , t h e o r g a n i c s u l f u r f u n c t i o n a l groups e x h i b i t e d one of t h r e e k i n d s o f b e h a v i o r : d i r e c t a u t o x i d a t i o n of t h e s u l f u r , i n d i r e c t o x i d a t i o n of t h e s u l f u r v i a a u t o x i d a t i o n of an a d j a c e n t , b e n z y l i c C-H bond; and no r e a c t i o n . T h i o l s and d i s u l f i d e s were d i r e c t l y o x i d i z e d t o s u l f o n a t e s which were s t a b l e u n d e r p r o c e s s c o n d i t i o n s ( i . e . no c a r b o n - s u l f u r bond c l e a v a g e ). Model compounds c o n t a i n i n g a b e n z y l i c s u l f i d e f u n c t i o n gave p r o d u c t s ( Equat ion 1 ) v i a a r e a c t i o n pathway which is ana logous t o t h e a u t o x i d a t i o n of b e n z y l i c C - H ' s i n d i a r y l m e t h a n e s ( Equat ion 2 ) . Other s u l f i d e s were recovered unchanged a f t e r one hour under Ames P r o c e s s c o n d i t i o n s . n

02, H20, N a CO e CH.SR - - - - > (f=$- !-R1 + RSO 3 -Na+

R = methyl o r phenyl , K' = H o r OH

0

Ar-C-Ar 0 2 , H Z O , Na CO I1 2 3 Ar-CH -AT /

150' C , 1 hour

The f u r t h e r e v a l u a t i o n of t h e Ames P r o c e s s w i t h model compounds h a s been aimed a t c o n s i d e r i n g t h e r e l a t i o n between d e s u l f u r i z a t i o n and t h e a u t o x i d a t i v e d e g r a d a t i o n of t h e s u b s t r a t e as a whole.

The e v a l u a t i o n of o x y d e s u l f u r i z a t i o n p r o c e s s e s u s i n g s i m p l e model compounds i s w e l l s u i t e d f o r d e t e r m i n i n g t h e r e a c t i v i t y o f p a r t i c u l a r f u n c t i o n a l g r o u p s , bu t does n o t s p e a k t o e f f e c t s on t h a t r e a c t i v i t y when such a r e p a r t of an ex tended hydrocarbon m a t r i x . The i n f l u e n c e o f t h e proximate environment on t h e o x i d a t i o n of s u l f u r f u n c t i o n s i s expec ted t o b e based on f a c t o r s such a s :

1) i n h i b i t i o n t o mass t r a n s p o r t of r e a g e n t s o r o x i d a t i o n p r o d u c t s ; 2) c o m p e t i t i v e r e a c t i v i t y by hydrocarbon f u n c t i o n s ; and

1 3 ) i n t r a m o l e c u l a r p r o p a g a t i o n of a u t o x i d a t i o n . I n o r d e r t o d e v i s e a model s u b s t r a t e f o r p r o c e s s e v a l u a t i o n i n which s u l f u r i s i n - c o r p o r a t e d i n a hydrocarbon m a t r i x w h i l e m a i n t a i n i n g t h e a b i l i t y t o d e s c r i b e t h e r e s u l t s i n terms of f u n c t i o n a l group r e a c t i v i t y , w e have p r e p a r e d a series o f syn- t h e t i c polymers which meet t h e r e q u i r e m e n t s o u t l i n e d below :

*Operated f o r t h e U.S. Department of Energy by Iowa S t a t e U n i v e r s i t y under C o n t r a c t No. W-7405-Eng-82. T h i s r e s e a r c h w a s s u p p o r t e d by t h e A s s i s t a n t S e c r e t a r y f o r Fos- s i l Energy, O f f i c e of Coal Mining, WPAS-AA-75-05-05.

155

1) a h i g h c a r b o n , hydrogen and s u l f u r c o n t e n t , 2) 3) s u f f i c i e n t c r o s s l i n k i n g t o i m p a r t i n s o l u b i l i t y .

a p r e d i c t a b l e a v e r a g e s t r u c t u r e , and

Such polymers s i m u l a t e some of t h e p h y s i c a l p r o p e r t i e s of c o a l and a l l o w t h e recovery o f t h e hydrocarbon c o n t e n t of t h e model as a s o l i d p r o d u c t , which procedure is a b a s i s of o x y d e s u l f u r i z a t i o n p r o c e s s e s .

Materials The m o d i f i c a t i o n , o u t l i n e d i n F i g u r e 1, of c h l o r o m e t h y l a t e d p o l y s t y r e n e beads

( Biobeads S-X1, 200-400 mesh, BioRad L a b o r a t o r i e s , Richmond, CA ) p r o v i d e s a con- v e n i e n t e n t r y t o s e v e r a l polymers meet ing t h e above r e q u i r e m e n t s as w e l l as b e i n g comparable one w i t h a n o t h e r . The p r e p a r a t i o n o f a formaldehyde condensa t ion poly- m e r ( F i g u r e 2 ) , which is c l o s e r than p o l y s t y r e n e t o t h e H / C r a t i o of c o a l s and is h i g h i n d i a r y l m e t h a n e f u n c t i o n s , was also c a r r i e d o u t a l t h o u g h t h i s polymer is less d e f i n e d as t o i ts a v e r a g e s i z e and s t r u c t u r e . S i m i l a r condensa t ion polymers , wi th- o u t s u l f u r , had p r e v i o u s l y been proposed as models f o r c o a l (5).

Exper imenta l The procedure by which t h e s y n t h e t i c polymers were s u b j e c t e d t o t h e Ames Pro-

cess is d e s c r i b e d h e r e . The d r y polymer, 0.6 t o 1.8 g, and 100 m l o f 0.2 M aqueous sodium c a r b o n a t e were p l a c e d i n a 300 m l a u t o c l a v e , which w a s f l u s h e d t h r e e t i m e s ' w i t h n i t r o g e n a t 80 p s i p r e s s u r e , and t h e s e a l e d a u t o c l a v e w a s h e a t e d t o t h e oper- a t i n g tempera ture . When t h e t e m p e r a t u r e had reached 150° C , oxygen w a s added t o a t o t a l p r e s s u r e of 200 p s i and t h e a u t o c l a v e was vented u n t i l t h e p r e s s u r e w a s about 1UO p s i . The a d d i t i o n o f oxygen w a s r e p e a t e d t w i c e , t h e n t h e s e a l e d a u t o c l a v e was s t i r r e d a t 1500 rpm f o r 1 h . w h i l e m a i n t a i n i n g t h e t e m p e r a t u r e a t 150 2 I n t h e c a s e of t h e s e polymers , n o s i g n i f i c a n t amount of material w a s l o s t by t h e vent - i n g procedure . A f t e r c o o l i n g t o room t e m p e r a t u r e t h e r e s i d u a l p r e s s u r e ( 70 t o 90 p s i ) was vented . The s o l i d w a s c o l l e c t e d by f i l t r a t i o n , u s i n g 400 ml of d i s t i l l e d water t o r i n s e t h e a u t o c l a v e and wash t h e s o l i d . The s o l i d w a s s u c c e s s i v e l y washed w i t h 30 m l p o r t i o n s of m e t h a n o l , THF and benzene , then d r i e d under reduced p r e s s u r e and 80 t o 90' C f o r a t l ea s t f i v e h. p r i o r t o weighing , r e c o r d i n g t h e I R spectrum ( K B r p e l . l e t ) and s u b m i t t i n g a sample f o r e l e m e n t a l a n a l y s i s ( e l e m e n t a l a n a l y s e s w e r e performed by G a l b r a i t h L a b o r a t o r i e s , K n o x v i l l e , TN ). The r e s i d u e obta ined by e v a p o r a t i o n of t h e combined o r g a n i c s o l v e n t s e x h i b i t e d PMR and I R s p e c t r a c h a r a c t e r - i s t i c o f p o l y s t y r e n e . I n t h e c a s e of (4-polys tyry1)methyl & - t o l y l s u l f i d e ( 1 ) , sodium 4 - t o l u e n e s u l f o n a t e i n t h e r e s i d u e of t h e aqueous phase was measured by its i n t e g r a l i n t e n s i t i e s i n t h e PMR spec t rum r e l a t i v e t o t-BuOH as a n i n t e r n a l s t a n d a r d . I n t h e c a s e of b e n z y l ( 4 - p o l y s t y r y l ) s u l f i d e ( 1. ) , t h e aqueous phase was e x t r a c t e d w i t h d ich loromethane and benzaldehyde w a s found t o be p r e s e n t i n the. ' x t r a c t i n a y i e l d of 19 % based on t h e amount of s u l f u r i n 2. R e s u l t s

The e f f e c t of t h e Ames P r o c e s s on t h e s y n t h e t i c polymers was monitored by t h e d e g r e e of s o l u b i l i z a t i o n and t h e e l e m e n t a l a n a l y s i s of t h e s o l i d p r o d u c t . For p o l y s t y r e n e s , t h e f o r m a t i o n of s o l u b l e polymers is a measure of t h e e x t e n t of a u t o x i d a t i o n of t h e p o i y s t y r y l backbone ( 6 ) ; t h i s d e g r a d a t i o n w i l l have no s i g n i - f i c a n t e f f e c t on t h e Sic r a t i o of t h e r e c o v e r e d s o l i d s . bond i s more s u s c e p t i b l e t o a u t o x i d a t i v e c l e a v a g e t h a n t h e polymer backbone t h a t a marked change i n t h e S / C r a t i o can o c c u r . - 1 ( T a b l e 1 ) and 2 ( T a b l e 2 ) which c o n t a i n t h e b e n z y l i c s u l f i d e f u n c t i o n . The d e c r e a s e i n t h e S/C r a t i o i n recovered polymer 1 and t h e i n c r e a s e i n t h i s r a t i o f o r recovered polymer - 2 is e x p l a i n e d by t h e f a c i l e a u t o x i d a t i o n r e a c t i o n s shown i n Equat ions 3 and 4 .

10' C.

I t i s only when a C-S

T h i s b e h a v i o r i s e x h i b i t e d by polymers

02, H 2 0 , Na CO b @CHO + C H 3 G S O 3 - N a +

150' C , 1 hour

3) @- CH2S a CH3

1 -

156

While t h e e x t e n t of d e s u l f u r i z a t i o n and polymer s o l u b i l i z a t i o n of 1 o v e r f o u r seemingly i d e n t i c a l r u n s ( T a b l e 1 ) were q u i t e v a r i a b l e , t h e r e i s a c o r r e l a t i o n between t h e two types o f d e g r a d a c i o n , i . e . more d e s u l f u r i z a t i o n w a s accompanied by more s o l u b i l i z a t i o n . That r a d i c a l i n i t i a t i o n of a u t o x i d a t i o n i s i m p o r t a n t f o r b o t h p r o c e s s e s was shown by t h e f a c t t h a t t h e i n c l u s i o n of a s p e c i f i c i n i t i a t o r , 2 , 2 ' - a z o b i s ( 2 - m e t h y l p r o p i o n i t r i l e ) ( A I B N ) , i n c r e a s e d both d e s u l f u r i z a t i o n and s o l u b i l i z a t i o n of polymer 1. i n c o n t r a s t , t h e u s e of AIBN w i t h 1 w a s c o u n t e r - p r o d u c t i v e w i t h r e s p e c t t o - - d e s u l f u r i z a t i o n . o u r ea r l ie r f i n d i n g s t h a t DBT is i n e r t to Ames P r o c e s s c o n d i t i o n s and w i t h o u r p o s t u l a t e t h a t C-S bond c l e a v a g e must be i n i t i a t e d by a u t o x i d a t i o n of an %-H.

When c o a l i s s u b j e c t e d to an o x y d e s u l f u r i z a t i o n p r o c e s s , i n d i g e n o u s l a b i l e f u n c t i o n s can presumably i n i t i a t e a u t o x i d a t i o n . I t h a s been r e p o r t e d f o r example, t h a t t h e p y r i d i n e s o l u b l e p o r t i o n of c o a l c o n t a i n s s u b s t a n c e s which promote t h e a i r o x i d a t i o n o f c o a l a t 100° C ( 7 ) . To test whetner a p y r i d i n e e x t r a c t of c o a l could i n i t i a t e t h e a u t o x i d a t i o n of 1, we added such a n e x t r a c t t o 1 under t h e c o n d i t i o n s of t h e Ames P r o c e s s . T h i s r e s u l t is r e p o r t e d i n Table 1 and l e a d s t o t h e c o n c l u s i o n t h a t t h e e x t r a c t was n o t a n e f f e c t i v e i n i t i a t o r of a u t o x i d a t i o n under t h e s e c o n d i t i o n s .

T h i s r e s u l t is e n t i r e l y c o n s i s t e n t w i t h

T a b l e 2 c o n t a i n s s u l f u r f u n c t i o n s which a r e i n e r t t o t h e p r o c e s s c o n d i t i o n s , i . e . DBT, DBTO and e t h y l phenyl s u l f o n e ; and , i n t h e s e sys tems, a u t o x i d a t i o n was n o t accompanie2 by d e s u l f u r i z a t i o n . t i o n poiymer 1, which i s p e r h a p s a b e t t e r model f o r c o a l tnan p o l y s t y r e n e (8) . The a b i l i t y of t h e Ames P r o c e s s t o o x i d i z e f l u o r e n e ( 4 ) sugges ted t h a t 1 should undergo a u t o x i d a t i o n . T h i s w a s e s t a b l i s h e d on t h e b a s i s o f t h e d e g r e e of s o l u b i l i - z a t i o n , I h e p r e s e n c e o f c a r b o n y l f u n c t i o n s i n t h e r e c o v e r e d s o l i d ( a s d e t e c t e d by l R , 1 7 1 5 cm-

Conclus ions

t h e s e r e a c t i o n c o n d i t i o n s promote a u t o x i d a t i o n of hydrocarbon f u n c t i o n s as w e l l , and t h e r e l a t i v e ra tes of hydrocarbon o x i d a t i o n and o r g a n i c s u l f u r removal a r e de te rmined by t h e p a r t i c u l a r s t r u c t u r e of each . Benzyl ic s u l f i d e s w e r e t h e o n l y c a s e examined where C-S bond c l e a v a g e was s i g n i f i c a n t p r e c i s e l y b e c a u s e of i ts g r e a t e r s u s c e p t i b i l i t y t o a u t o x i d a t i o n r e l a t i v e t o t h e hydrocarbon p a r t of t h e polymer. When i n c o r p o r a t e d i n t o a hydrocarbon polymer, b e n z y l i c s u l f i d e s were found t o be less r e a c t i v e under t h e p r o c e s s c o n d i t i o n s t h a n t h e monomer b e n z y l phenyl s u l f i d e ( 4 ) . There is no i n d i c a t i o n t h a t t h e hydroperoxides , which a r e formed by a u t o x i d a t i o n o f l a b i l e C-H bonds, r e a c t w i t h s u l f i d e s t o produce s u l f o x i d e s o r s u l f o n e s under t h e s e c o n d i t i o n s .

T h i s i s e s p e c i a l l y e v i d e n t w i t h t h e condensa-

) and t h e i n c o r p o r a t i o n of oxygen i n t h e s o l i d .

Although t h e Ames P r o c e s s w a s des igned t o o x i d i z e and remove s u l f u r from c o a l ,

I n t h i s e v a l u a t i o n of t h e Ames P r o c e s s w i t h polymer models , w e have shown t h a t :

1) only b e n z y l i c s u l f i d e s undergo p r e f e r e n t i a l C-S bond c l e a v a g e ;

2) t h i s c l e a v a g e i s a r a d i c a l p r o c e s s ana logous t o hydrocarbon a u t o x i d a t i o n ;

3 ) c o n d i t i o n s which accelerate t h e o x i d a t i v e c l e a v a g e of t h e s e C-S bonds w i l l a l s o i n c r e a s e t h e ra te of d e g r a d a t i o n of t h e hydrocarbon m a t r i x ;

43 a s e x p e c t e d , t h e r a t e of r e a c t i o n of t h e b e n z y l i c C-S bond i s a t t e n u a t e d when t h e s u l f i d e i s i n c o r p o r a t e d i n t o an i n s o l u b l e polymer.

157

Figure 1. Synthesis of Modified Polystyrenes for Use as Coal Models.

2) ' ) "-'lILi benzyl > " S - C H 2 G

d i s u l f i d e

2: 83.24 %C. 7.11 % H . 8.40 %S, 1.12 %Br

DBT,ZnCI2

C6H4C'2 @-CH2CI - @CH2 CH2-@

1: 87.59 %C, 6.82 %H, 4.58 %S

C1C6H4COgH

CH2-@

O'"2Qs@ 1 HCC13 >

o" \\o

2: 83.78 %C, 6.61 %H, 4.44 % S

Figure 2.

5: 80.82 % C , 7.25 %H, 5.84 %S

Hypothetical Structure for DBT/Fluorene/Formaldehyde Copolymer

- 7: 86.72 %c, 5.01 zn, 7.75 zs 158

TABLE 1. E f f e c t of Ames P r o c e s s on (4-Polys tyry1)methyl 4-Tolyl S u l f i d e ( 1 ) .a

d Initial Wgt. Recovered as a S o l i d % CH2-SC 4-Tolyl S o l u b l e

Weight Carbon S u l f u r AS/C Cleavage S u l f o n a t e Polymer

0.91 g 84 % 81 % 57 % -30 % 37 % 22 % 4 . 5 %

0.91 92 90 76 -16 21 28 2 . 1

1.14 93 91 76 -17 22 18 1.7

0.60 92 93 92 - 1 2 0 . 3 0

90 8 9 75 -16 20 a v e r a g e of f o u r

1. 0oe 84 8 8 76 -13 17

0.74f 86 83 54 -34 42

17 2.2

- 9.3

TABLE 2 . E f f e c t of Ames P r o c e s s on Some S y n t h e t i c Polymers .a

b Initiai Wgt. Recovered a s a S o l i d _ _ _ _ _

P o l y s t y r e n e g 1.59 g 96 % 96 %

1.50 95 -

2 0.62 87 84

- 3 0.78 96 96

- 4 0 .73 104 101

-

- 5 1.16 94 95

- 7 1.06 89 87

- 7f 0.90 95 92

- - - -

98 % +17 %

97 + 1

02 + 1

96 + 1% 88 + 2

95 + 5

d S o l u b l e Polymer

2.3 %

0.7

3 . 2

1 .4

1.0

0

9.4

4 .0

See F i g u r e s 1 and 2 f o r t h e s t r u c t u r e s of t h e polymers . P r e s e n t e d a s a p e r c e n t a g e of t h e c o r r e s p o n d i n g o r i g i n a l v a l u e s . T h i s is based on t h e i o s s of s u l f u r r e l a t i v e t o t h e p o l y s t y r y l c a r b o n , which i s t h e t o t a l carbon l e s s t h e carbon due t o t h e 4 - t o l y l g r o u p s , and is c a l c u l a t e d a s 100 % - 100 % ( S C - 75 S . ) + ( S.C - 7 s S . )

where S is t h e moles p e r u n i t weight of S u l f u r i n t h e s o l i d p r o d u c t ,

S . i s t h e moles of s u l f u r i n t h e i n i t i a l polymer, C . i s t h e moles of

carbon i n t h e i n i t i a l polymer and C is t h e moles of carbon i n t h e s o l i d

Residue a f t e r e v a p o r a t i o n of t h e o r g a n i c s o l v e n t s a s a p e r c e n t a g e of t h e i n i t i a l weight . P y r i d i n e e x t r a c t of a n Ill. No. 6 c o a l , 0.1 g , was added t o t h i s r u n ; t h e p r e s e n c e of t h e e x t r a c t masked d e t e c t i o n of s o l u b l e polymer. With 0.16 g of AIBN added and oxygen added b e f o r e h e a t i n g t h e a u t o c l a v e . Biobeads S-X1, 200-400 mesh, prewashed w i t h benzene and MeOH. N2 a tmosphere o n l y i n s t e a d of 02;

P i P I 1 P P l

P

p r o d u c t . P

e l e m e n t a l a n a l y s i s n o t o b t a i n e d .

159

REFERENCES

1.

2.

3.

4 .

5.

6. 7.

8 .

( a ) S. Fr iedman, R .B . LaCount and R.P. W a r z i n s k i , i n Coal D e s u l f u r i z a t i o n , ‘T .D . Wheelock, e d . , A . C . S . Symposium S e r i e s , 9, 164-172 (1977) ; (b) S . S a r e e n , i b i d . , 173-181; ( c ) C.Y. T a i , G . V . Graves and T .D. Wheelock, i b i d . , 182-197. T.D. Wheelock, R.T. Greer, R . Markuszewski and R.W. F i s h e r , Advanced Develop- ment of F i n e Coal D e s u l f u r i z a t i o n and Recovery Technology, Annual Technica l P r o g r e s s R e p o r t , O c t . 1, 1976-Sept. 30, 1977, s u b m i t t e d t o t h e U . S . Department of Energy, Ames L a b o r a t o r y , Iowa S t a t e U n i v e r s i t y , Document No. IS-4363, March. 1978. B. P a r i s , i n Coal D e s u l f u r i z a t i o n , T.D. Wheelock, e d . , A.C.S. Symposium S e r i e s , 64, 22-31 ( 1 9 7 7 ) . T.G. S q u i r e s , C . G . V e n i e r , L.W. Chang and T.E. Schmidt , ACS Div. Fue l Chem.,

( a ) P. Wolfs , D. Van Krevelen and H. Waterman, Brennstoff-Chemie, 40, 215-222, PREPRINTS, 26, No. I, 50-55 (1981) .

~

(1959) ; ( b ) L. Lazrov and S . Angelov, F u e l , 59, 55-58 (1979) . L. Dulog and K.-H. David , D i e Makromolekulare Chemie, 145, 67-85 (1971) . V . A . Sukhov, e t . a l . , S o l i d F u e l Chemistry ( t r a n s . of Khim. Tverd. T o p l . ) ,

K.-D. Gundermann, G. F l e d l e r and I. Knoppel, Brennstoff-Chemie, 2, 23-27 (1976) . - 10, ( 3 ) , 96-100 (1976) .

160

PRODUCT Y I E L D AND HYDROGEN CONSUMPTION SELECTIVITY TESTS FOR COAL LIQUEFACTION CATALYST DEVELOPMENT*

H. P. S tephens

Sandia Na t iona l L a b o r a t o r i e s , Albuquerque, N e w Mexico 87185

INTRODUCTION

Because hydrogenat ion o f c o a l t o l i q u i d p roduc t s ( o i l s ) i s accompanied by d i s t r i b u t i o n s o f complex by-product m i x t u r e s ( I O M , p r e a s p h a l t e n e s , a s p h a l t e n e s and g a s e s ) which change as a f u n c t i o n of r e a c t i o n v a r i a b l e s ( t i m e , t empera tu re and p r e s s u r e ) and r e a c t o r con- f i g u r a t i o n , t h e de t e rmina t ion o f s e l e c t i v i t y r e l a t i o n s h i p s f o r coal l i q u e f a c t i o n c a t a l y s t s h a s been a d i f f i c u l t and time-consuming t a s k i n v o l v i n g numerous exper iments t o adequa te ly d e s c r i b e c a t a l y s t pe r - formance ove r a range of c o n d i t i o n s . This paper d e s c r i b e s a method f o r ana lyz ing t h e expe r imen ta l r e s u l t s o f c o a l l i q u e f a c t i o n r e a c t i o n s which may be a p p l i e d t o a number of a s p e c t s of c o a l l i q u e f a c t i o n r e s e a r c h and p r o c e s s c o n t r o l , i n c l u d i n g : r a p i d s e l e c t i v i t y and pe r - formance sc reen ing f o r c a t a l y s t s : c o r r e l a t i o n o f l a b o r a t o r y r e s u l t s w i th p rocess pa rame te r s ; and o p t i m i z a t i o n o f product y i e l d fo r p l a n t p rocess c o n d i t i o n s . C a t a l y s t s e l e c t i v i t y and performance s c r e e n i n g w i l l be emphasized h e r e .

A primary goa l o f c a t a l y s t development f o r d i r e c t c o a l l i q u e f a c - t i o n i s t o maximize t h e y i e l d o f d i s t i l l a t e p roduc t s wh i l e minimizing t h e convers ion t o by-product hydrocarbon g a s e s which u n p r o f i t a b l y consume much o f t h e hydrogen. S e l e c t i v i t y r e l a t i o n s h i p s f o r d i r e c t c o a l l i q u e f a c t i o n c a t a l y s t s have been d i f f i c u l t t o de t e rmine and a c c u r a t e l y d e s c r i b e , n o t o n l y because of t h e complexity of t h e r e a c t i o n mix tu res , bu t a l s o because o f t h e d i f f i c u l t y o f comparing t h e r e s u l t s of exper iments performed a t d i f f e r e n t times and t empera tu res o r wi th d i f f e r e n t t y p e s of reactors. Imprec is ion i n c o n t r o l of expe r imen ta l v a r i a b l e s such a s t empera tu re and c o n t a c t t i m e o f t e n c a u s e s s i g n i f i c a n t d i f f e r e n c e s i n conve r s ions f o r exper iments f o r which t h e mean v a r i a b l e s were des igned t o be nominal ly t h e same. Thus s e l e c t i v i t y comparisons based on convers ions a t c o n s t a n t t i m e and t empera tu re a r e n o t e n t i r e l y r e l i a b l e .

The approach t o s e l e c t i v i t y r e l a t i o n s h i p s d e s c r i b e d i n t h i s paper i s based on 1) a t e r n a r y p roduc t d i s t r i b u t i o n diagram wi th a h y p e r b o l i c re 1 a t i on

between product and by-product conve r s ions and 2 ) a hydrogen consump- t i o n diagram which r e l a t e s t h e p roduc t convers ion t o t h e f r a c t i o n of hydrogen consumed by t h e p roduc t ion of hydrocarbon gases . Each o f t h e s e diagrams correlates, on a s i n g l e c u r v e , p roduct d i s t r i b u t i o n s from r e a c t i o n s carried o u t o v e r a wide range of expe r imen ta l pa ra - me te r s , i n c l u d i n g t empera tu re , t i m e and d i f f e r e n t r e a c t o r s .

waterman f i r s t used t e r n a r y product d i s t r i b u t i o n diagrams wi th r e a c t i o n p a t h s r e p r e s e n t e d by

x(1-x) y = a + b x 2 )

* This work suppor ted by t h e U . S . Department o f Energy.

161

t o d e s c r i b e t h e c a t a l y t i c hydro i somer i za t ion o f p a r a f f i n wax (1) and la te r demonst ra ted t h e i r a p p l i c a t i o n t o t h e c h a r a c t e r i z a t i o n o f many o t h e r complex chemica l p r o c e s s e s ( 2 ) . Although t h e t echn ique has been used t o d e s c r i b e o t h e r hydrogenat ion p r o c e s s e s ( 2 , 3 ) , a p p l i - c a t i o n t o d i r e c t c o a l l i q u e f a c t i o n has been unexplored. The r e s u l t s and a n a l y s i s of d i r e c t c o a l l i q u e f a c t i o n expe r imen t s d e s c r i b e d i n t h i s paper demons t r a t e t h e g e n e r a l a p p l i c a b i l i t y o f t e r n a r y and hydrogen consumption d iagrams t o s e l e c t i v i t y tests f o r c o a l l i q u e - f a c t i o n c a t a l y s t development.

EXPERIMENTAL

Mater i a1 s

L ique fac t ion r e a c t i o n s were performed wi th I l l i n o i s N o . 6 c o a l , SRC-I1 heavy d i s t i l l a t e from t h e F t . L e w i s p i l o t p l a n t ( 1 : 2 coa1:so l - v e n t , by we igh t ) and h i g h p u r i t y hydrogen. An e x t e n s i v e l y used commercial HDS c a t a l y s t , American Cyanamid 1 4 4 2 A , an alumina suppor ted CoMo fo rmula t ion , was t e s t e d t o e s t a b l i s h b a s e - l i n e s e l e c t i v i t y r e l a t i o n s h i p s . T h e c a t a l y s t e x t r u d a t e s w e r e ground t o a -200 mesh powder and added t o t h e r e a c t i o n f e e d s l u r r y on a 5 weight pe rcen t coal b a s i s . This q u a n t i t y o f CoIBo/alumina was e q u i v a l e n t t o 0.15% Co and 0.45% M o . To t es t t h e u t i l i t y of t h e s e l e c t i v i t y r e l a t i o n - s h i p s , a d d i t i o n a l m i c r o r e a c t o r exper iments were performed w i t h 0.3% Mo a s molybdenum naph thena te ( 6 % s o l u t i o n o f molybdenum i n naph then ic a c i d , ob ta ined from Research Organic/Research I n o r g a n i c , I n c . ) , a long wi th a c o n t r o l expe r imen t w i t h t h e e q u i v a l e n t amount o f naphthenic a c i d a lone .

Apparatus and P rocedure 3 Two t y p e s o f reactor sys tems w e r e u t i l i z e d , 30 cm b a t c h micro-

r e a c t o r s ( 4 1 , and a o n e - l i t e r a u t o c l a v e ( 5 ) . F o r t h e l o w t o moderate conve r s ion range , microreactor exper iments were performed a t 1000 p s i g c o l d charge hydrogen p r e s s u r e and o v e r a wide range o f t i m e s , t = 0 .5 to 80 min, and t e m p e r a t u r e s , T = 350° t o 425OC. Two auto- c a l v e exper iments were conducted a t 1000 p s i g and 425OC f o r 30 and 120 min t o o b t a i n d a t a f o r h igh conve r s ions . Temperatures and p res - s u r e s were a c c u r a t e l y r eco rded d u r i n g t h e c o u r s e o f each experiment. Following t h e h e a t i n g p e r i o d o f each expe r imen t , t h e r e a c t i o n v e s s e l was quenched t o ambient t empera tu re , t h e r e s u l t i n g p r e s s u r e was r e c o r d e d , a gas sample w a s t a k e n , and t h e p roduc t s l u r r y w a s quan t i - t a t i v e l y t r a n s f e r r e d t o a f l a s k and subsampled f o r a n a l y s i s .

P roduc t Ana lys i s

G a s samples w e r e ana lyzed f o r mole p e r c e n t a g e s o f CO, CO , H S and C1-C4 hydrocarbons w i t h a Hewlett-Packard 5710A g a s chromitoggaph, which was c a l i b r a t e d w i t h s t a n d a r d m i x t u r e s o f hydrocarbon gases and H S i n hydrogen, o b t a i n e d from Matheson G a s Products . Hydrogen i n tge samples was o b t a i n e d by d i f f e r e n c e a s t h e remainder o f t h e pro- d u c t gas mixture . T h e q u a n t i t y of each g a s produced w a s c a l c u l a t e d from t h e mole p e r c e n t i n t h e g a s sample and t h e p o s t - r e a c t i o n v e s s e l t empera tu re T and p r e s s u r e P u s i n g an i d e a l g a s l a w c a l c u l a t i o n :

w = FW. ni 4 ) i

162

where n = number o f moles o f component i i f i = mole f r a c t i o n o f i i n t h e gas sample = mole % / l o 0

v = gas volume o f r e a c t o r w. = weight o f i

FWi = t h e formula weight o f i

Hydrogen consumed d u r i n g t h e r e a c t i o n was o b t a i n e d a s t h e d i f f e r e n c e between t h e i n i t i a l charge and hydrogen remain ing a f t e r t h e reactor w a s quenched.

The r e a c t i o n p roduc t s l u r r y w a s ana lyzed f o r i n s o l s , p reaspha l - t e n e s , a s p h a l t e n e s , and o i l s by t e t r a h y d r o f u r a n (THF) s o l u b i l i t y and h igh performance l i q u i d chromatography (HPLC). A 0 . 2 gm subsample was mixed w i t h about 50 m l o f THF, f i l t e r e d t o o b t a i n t h e we igh t of i n s o l s , and brought t o 100 m l w i th a d d i t i o n a l THF. Chromatograms o f 5 p i a l i q u o t s of t h e f i l t r a t e were o b t a i n e d wi th a Waters Assoc. Model 6000A s o l v e n t d e l i v e r y sys tem equipped w i t h a Model 4 4 0 uv absorbance d e t e c t o r . S e p a r a t i o n s o f t h e s o l u t i o n i n t o t h r e e , f r a c t i o n s , p r e a s p h a l t e n e s , a s p h a l t e n e s , and o i l s , were e f f e c t e d on 100 A micro- s y r a g e l g e l permeation columns. The uv absorbance response f a c t o r s fo r t h e p roduc t s e p a r a t i o n s were de termined u s i n g s t a n d a r d s p repa red by d i s s o l v i n g known amounts of p r e a s p h a l t e n e s , a s p h a l t e n e s and o i l s o b t a i n e d by s o x h l e t s e p a r a t i o n o f whole l i q u i d product from p repa ra - t o r y l i q u e f a c t i o n exper iments ( 6 ) . Peak h e i g h t measurement and response f a c t o r s w e r e used t o c a l c u l a t e t h e pe rcen tages o f p reaspha l - t e n e s , a s p h a l t e n e s and o i l s f o r t h e THF s o l u b l e product . A l l y i e l d and convers ion d a t a were c a l c u l a t e d on a d ry mine ra l m a t t e r - f r e e (dmmf) c o a l b a s i s , which i n c l u d e d a c o r r e c t i o n f o r t h e conve r s ion of p y r i t e con ten t o f t h e c o a l t o p y r r h o t i t e .


Process Course and S e l e c t i v i t y

Two t e r n a r y diagrams of product/by-product d i s t r i b u t i o n s f o r t h e c o a l l i q u e f a c t i o n exper iments p r e v i o u s l y d e s c r i b e d a r e shown i n F i g u r e s 1 and 2. Conversion d a t a f o r t h e v a r i o u s exper iments a r e r e p r e s e n t e d by t h e fo l lowing symbols-- 0 Co/Mo c a t a l y z e d ; Mo-naph- t h e n a t e c a t a l y z e d ; and 0 naph then ic a c i d b lank . In F igu re 1, a s p h a l t e n e convers ion i s p l o t t e d a g a i n s t o i l convers ion (both w t % dmmf b a s i s ) and i n F i g u r e 2 , t h e sum of mole p e r c e n t o i l and a spha l - t e n e convers ion i s p l o t t e d vs m o l e p e r c e n t hydrocarbon q a s conver- s i o n . Becawe of the l a r g e d i f f e r e n c e between molecular weight of gases (CH t o C H -- 16-58) and o t h e r p roduc t s ( e .g . , o i l s - -200 t o 4 0 0 ) , t he lmole behgent b a s i s i s used t o more p r e c i s e l y r e p r e s e n t t h e t e r n a r y diagrams invo lv ing hydrocarbon gases . For t h e purpose o f c a l c u l a t i n g mole p e r c e n t a g e s , average molecular we igh t s o f 2400, 1200, 600 and 300 w e r e assumed f o r t h e f r a c t i o n s o f I O M , p reaspha l - t e n e s , a s p h a l t e n e s and o i l s . These v a l u e s approximate ly co r re spond t o t h e middle of t h e molecu la r weight d i s t r i b u t i o n r anges f o r t h e s e f r a c t i o n s (7). Moles o f g a s e s produced were expe r imen ta l ly d e t e r - mined as p r e v i o u s l y desc r ibed .

F i g u r e s 1 and 2 i l l u s t r a t e s e v e r a l g e n e r a l o b s e r v a t i o n s which can be made about t h e c o a l l i q u e f a c t i o n p rocess . F i r s t , a l t hough t h e l i q u e f a c t i o n p rocess i s complex, i n v o l v i n g myriad chemical s p e c i e s , i ts c o u r s e can be q u a n t i t a t i v e l y d e s c r i b e d by s imple diagrams r e l a t i n g groups o f compounds which r e a c t i n s i m i l a r and p r e d i c t a b l e manners.

163

These d iagrams may rough ly be cons ide red t h e k i n e t i c ana log o f e q u i l i b r i u m phase d iagrams i n which t h e number o f components o f a sys tem i s t h e smallest number o f i ndependen t ly v a r i a b l e c o n s t i t u e n t s . The composi t ion of t h e l i q u e f a c t i o n r e a c t i o n mix tu re i s g iven by the f r a c t i o n s e x p l i c i t l y r e p r e s e n t e d by t h e x and y axes , and a remainder p o r t i o n r e p r e s e n t e d by t h e l e n g t h o f a h o r i z o n t a l t i e l i n e from a p o i n t on t h e cu rve t o t h e d i agona l a x i s c o n n e c t i n g t h e x and y axes . For F igu re 1, a s p h a l t e n e and o i l conve r s ion are g iven by t h e y and x a x i s and p r e a s p h a l t e n e , I O N and gases by t h e t i e l i n e . Second, t h e hype rbo l i c r e l a t i o n s h i p s f o r t h e conve r s ion o f t h e f r a c t i o n s shown i n t h e f i g u r e s r e p r e s e n t un ique r e a c t i o n p a t h s f o r t h e . Co/Mo c a t a l y z e d r e a c t i o n s , over a wide r ange o f o p e r a t i n g cond i t ions - - t ime , tempera- t u r e and r e a c t o r t y p e . Dev ia t ions from t h i s hyperbola r e p r e s e n t c o n d i t i o n s which change t h e p r o c e s s c o u r s e , f o r example, t h e o n s e t o f competing p y r o l y s i s r e a c t i o n s a t h igh t empera tu res which form coke and gas . T h i s i n d i c a t e s t h a t t h e s e l e c t i v i t y f o r a c o a l l i q u e f a c t i o n c a t a l y s t , w i t h r e s p e c t t o product groups , may b e un ique ly d e s c r i b e d by h y p e r b o l i c r e l a t i o n s h i p s . Support f o r t h i s h y p o t h e s i s is g iven by t h e a n a l y s i s o f t h e s e l e c t i v i t y f o r a set o f t w o u n i d i r e c t i o n a l , consecu t ive r e a c t i o n s f o r which t h e s e l e c t i v i t y may be d e s c r i b e d by r e l a t i v e c o n c e n t r a t i o n s g iven by h y p e r b o l i c e q u a t i o n s o f one c o n s t a n t ( 2 , 8 ) .

exempl i f i ed by F i g u r e s 1 and 2 i s t h a t t h e y may be used t o r a p i d l y s c r e e n f o r c a t a l y s t s e l e c t i v i t y . Once h y p e r b o l i c r e l a t i o n s are d e r i v e d f o r a b a s e l i n e c a t a l y s t , t h e s e l e c t i v i t y o f ano the r c a t a l y s t may be screened by comparison o f i t s product/by-product d i s t r i b u t i o n s f o r one o r two expe r imen t s w i th t h e hype rbo la o f t h e b a s e l i n e c a t a l y s t . I t can be s e e n i n F igu re 1 t h a t t h e p o i n t f o r t h e M o naph thena te expe r imen t f a l l s below t h e cu rve f o r Co/Mo b u t above t h e b lank exper iment . T h i s i n d i c a t e s t h a t t h e o r d e r of a s p h a l t e n e t o o i l s e l e c t i v i t y i s :

Blank < Mo-naphthenate < Co/Mo.

I n F igu re 2 , t h e sum of t h e coal conve r s ion p r o d u c t s , o i l s and a s p h a l t e n e s , a r e p l o t t e d a s a f u n c t i o n of unwanted by-product hydrocarbon gas conve r s ion . Again, t h e Mo-naphthenate p o i n t f a l l s between t h e Co/Mo c u r v e and t h e b lank . Thus Mo-naphthenate, a t t h e concen- t r a t i o n used i s n o t a s s e l e c t i v e f o r a s p h a l t e n e and o i l convers ion as Co/Mo, b u t does promote a bet ter product/by-product r a t i o t h a n t h e non-ca ta lyzed exper iment .

Hydrogen Consumption Diagram

The u t i l i t y o f t e r n a r y diagrams and h y p e r b o l i c r e l a t i o n s h i p s

Another u s e f u l r e l a t i o n s h i p developed t o de t e rmine t h e e f f i c i e n c y or s e l e c t i v i t y o f a hydrogenat ion c a t a l y s t w i t h r e s p e c t t o p r o c e s s hydrogen consumption i s i l l u s t r a t e d i n F igu re 3 , a p l o t of t h e sum of o i l and a s p h a l t e n e conve r s ion ( w t % , dmmf) as a f u n c t i o n o f t h e f r a c t i o n of hydrogen consumed by p roduc t ion of hydrocarbon gases ( t h e r a t i o of t h e weight o f hydrogen i n t h e hydrocarbon gases t o t h e hydrogen consumed). Again, a wide range o f expe r imen ta l c o n d i t i o n s f o r hydrogenat ion of coal c a t a l y z e d by Co/Mo can be r e p r e s e n t e d by a s i n g l e cu rve . T h i s diagram p rov ides a more s i g n i f i c a n t s e l e c t i v i t y t e s t than t h e h y p e r b o l i c c o r r e l a t i o n s i n t h a t i t r e l a t e s d i r e c t l y t o a primary g o a l of c a t a l y s t development fo r d i r e c t c o a l l i q u e f a c t i o n - - maximizing the y i e l d of d i s t i l l a t e p r o d u c t s w i th r e s p e c t t o hydrogen consumption. F i g u r e 3 i l l u s t r a t e s t h a t hydrogenat ion e f f i c i e n c y o f Co/Mo-catalyzed conve r s ion o f c o a l t o o i l and a s p h a l t e n e s s h a r p l y

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d e c r e a s e s above conve r s ions o f about 80%. P o i n t s r e p r e s e n t i n g exper iments f o r o t h e r c a t a l y s t s f a l l i n g below t h e Co/Mo cu rve i n d i - cate t h a t t h e s e c a t a l y s t s are less e f f i c i e n t t han Co/Mo w i t h r e s p e c t t o hydrogen consumption. The p o i n t r e p r e s e n t i n g t h e Mo-naphthenate experiment f a l l s close t o t h e Co/Mo cu rve i n d i c a t i n g an e f f i c i e n c y n e a r l y e q u a l to Co/Mo, wh i l e t h e b lank exper iment (naph then ic a c i d ) shows t h a t non-catalyzed c o a l convers ion i s much less e f f i c i e n t i n hydrogen consumption.

REFERENCES

1. F. B r e i m e r , H. I. Waterman and A. B. R. Weber, J. I n s t . Pe t ro leum, 43, 297 (1957) . -

2 . H. I. Waterman, C. Bodhouwer and D. Th. A. Huibers , "Process C h a r a c t e r i z a t i o n " , E l s e v i e r , New York, 1960.

3. L. C. Doelp, N. Brenner , and A. H. Weiss, I & E C Proc. D e s . Dev. 4,

4 . M. G. Thomas and D. G . Sample, " C a t a l y s t C h a r a c t e r i z a t i o n i n Coal

92 (1965) .

L i q u e f a c t i o n " , SAND-80-0123, Sandia Na t iona l L a b o r a t o r i e s , June 1980.

5. B. Granoff , e t a l . , "Chemical S t u d i e s on t h e S y n t h o i l P rocess : Mineral Matter E f f e c t s , " SAND-78-1113, Sandia Na t iona l Labora tor - ies, June 1978.

6 . A. W. Lynch, Sandia Na t iona l L a b o r a t o r i e s , p e r s o n a l communication, 1981.

7. D. D. Whi t ehur s t , M. F a r c a s i u and T. 0. M i t c h e l l , "The Nature and Or ig in o f Asphal tenes i n Processed C o a l s , " EPRI AF-252, February 1976.

8. A. H. Weiss, "Cons idera t ions i n t h e Study of Reac t ion S e t s , " C a t a l y s i s Reviews 2, 1972.

Number 1 2 3 , 4 5 6 I 8 9

1 0 11 1 2

Key t o F i q u r e s

Reac tor C a t a l y s t T ( " C )

Micro 350

425 400 425 425 425 425

Au t o c l ave 425 425

Micro Mo-Naphth 425 Blank 425

t Co!Mo 375

t

I t I,

I,

I

t (min)

15 15

0.5 1 5 10 1 5 40 80 30

1 2 0 30 30

165

O i l Conversion Vieioht %, dmmf)

F igu re 1. Ternary diagram of a s p h a l t e n e vs . o i l conve r s ion . The curve , g iven by t h e equa t ion

x(95-x) = 16.9+1.00x

r e p r e s e n t s t h e process cour se f o r t h e Co/Mo c a t a l y z e d exper iments .

0

Hydrocarbon Gas Conversion (Hole $ 1

Figure 2 . Ternary diagram o f t h e sum of aspha l - t e n e and o i l conve r s ion vs . hydrocarbon gas conver- s i o n . The cu rve i s g iven by t h e e q u a t i o n

x (100-x) = 2.35+1.15x

E 4 m 80 (u > - -"I 60 4 ..-I

0 2 + U

a m E -4

(uo U 3 4-

c 4 0

c" 20 E

100 8

10

O 1 2

0 20 40 60 80 1 0 0

Weight IT i n C -C Hydrocarbons 1 4 Weight Hydrogen Consumed

x 100

n

F i g u r e 3 . Hydrogen consumption diagram f o r d i r ec t c o a l l i q u e f a c t i o n exper iments . Curve r e p r e s e n t s Co/Mo c a t a l y z e d exper iments .

166

The E f f e c t of P r e s s u r e and Gas Composition on t h e F l u i d i t y of P i t t s b u r g h No. 8 Coal

M . S . Lancet F. A , Sim

Conoco Coal Development Company Research D i v i s i o n

L i b r a r y , PA 15129

INTRODUCTION

The G i e s e l e r method(') of measuring t h e f l u i d i t y of c o a l h a s long been a parameter used by t h e s t e e l i n d u s t r y f o r t h e e v a l u a t i o n of coke oven feeds tocks . T h i s a n a l y t i c a l t echnique i n which t h e r o t a t i o n a l speed of a r a b b l e arm s t i r r e r he ld i n a packed sample of ground c o a l i s measured a s i t i s t w i s t e d w i t h a known t o r q u e whi le t h e sample i s hea ted t h r o u g h t h e p l a s t i c r a n g e , i s a measure of t h e pseudo v i s c o s i t y of t h e molten or semi-molten c o a l .

The i n t e r e s t i n r e c e n t y e a r s i n t h e g a s i f i c a t i o n of E a s t e r n U.S. bi tuminous c o a l s h a s l e d t o concern over p o t e n t i a l coking and handl ing problems of t h e s e c o a l s a s t h e y a r e fed t o t h e g a s i f i e r . Conoco 's e x p e r i e n c e w i t h t h e g a s i f i c a t i o n o f two h ighly f l u i d E a s t e r n c o a l s d u r i n g t h e DOE sponsored Technica l Support Program f o r t h e B r i t i s h Gas/Lurgi s l a g g i n g g a s i f i e r p r o j e c t suggested t h a t t h e s e c o a l s demonst ra te s i g n i f i c a n t l y d i f f e r e n t coking and f l u i d i t y p r o p e r t i e s under g a s i f i e r c o n d i t i o n s t h a n they do a t s tandard a tmospher ic c o n d i t i o n s . Hence Conoco began a program f o r t h e e v a l u a t i o n o f g a s i f i e r f e e d s t o c k s which i n c l u d e s examining t h e coking p r o p e r t i e s a t s imula ted g a s i f i e r c o n d i t i o n s .

A s a p a r t of t h i s o v e r a l l program Conoco h a s designed and b u i l t a p r e s - s u r i z e d Gieseler Plas tometer i n which it i s p o s s i b l e t o measure t h e f l u i d i t y of c o a l s i n a tmospheres o f any d e s i r e d composi t ion and a t t o t a l p r e s s u r e s up t o 450 p s i g . The i n i t i a l s e r i e s of tests i n t h i s a p p a r a t u s , r e p o r t e d h e r e , i s a s tudy of t h e e f f e c t of n i t r o g e n and hydrogen p r e s s u r e on t h e f l u i d i t y of a P i t t s b u r g h No. 8 seam c o a l . Ni t rogen was chosen a s a n " i n e r t " g a s t o examine only t h e e f f e c t of t o t a l p r e s s u r e while hydrogen - probably t h e most r e a c t i v e g a s i n a g a s i f i e r - was chosen a s a f i r s t approximation t o a g a s i f i e r g a s .

EXPERIMENTAL

Appara tus -- The b a s i c a p p a r a t u s c o n s i s t s o f a S tandard I n s t r u m e n t a t i o n Model P-11R

r e s e a r c h v e r s i o n G i e s e l e r P l a s t o m e t e r w i t h t h e measuring head and s o l d e r p o t mounted i n a p r e s s u r e v e s s e l and t h e a s s o c i a t e d e l e c t r o n i c s l o c a t e d e x t e r n a l l y . F i g u r e 1 i s a d e s i g n drawing of t h e a p p a r a t u s . The p r e s s u r e v e s s e l i s f a b r i c a t e d from a 30" long , 10" d i a schedule 4 0 p i p e , capped a t t h e bottom and f l a n g e d a t t h e t o p . A s o l d e r p o t r e s t s on a p e r f o r a t e d s t e e l p l a t e a t t h e bottom and t h e measur- i n g head and c r u c i b l e assembly a r e suspended from t h e t o p f l a n g e . A s i g h t gauge i s provided t o i n s u r e p r o p e r a l ignment d u r i n g t h e lower ing of t h e c r u c i b l e i n t o t h e s o l d e r p o t .

E l e c t r i c a l l e a d s a r e passed i n t o t h e p r e s s u r e s h e l l th rough conax p r e s s u r e s e a l f i t t i n g s . The v e s s e l i s p r e s s u r i z e d through a h a l f i n c h i n l e t p o r t and t h e p r e s s u r e i s monitored d u r i n g a r u n v i a a 0-600 p s i g p r e s s u r e i n d i c a t o r . The v e s s e l h a s a p r e s s u r e r e l i e f v a l v e s e t a t approximately 5 5 0 p s i g t o i n s u r e a g a i n s t a c c i d e n t a l over p r e s s u r i z a t i o n . F igure 2 i s a f low diagram f o r t h e pres - s u r i z e d G i e s e l e r p l a s t o m e t e r a t Conoco Coal Development Company.

167

P r o c e d u r e

The c o a l i s sampled, ground and packed i n t o t h e c r u c i b l e i n t h e s tandard The packed c r u c i b l e assembly i s t h e n connected t o t h e measuring head manner.(')

and t h e whole assembly i s lowered, a long w i t h t h e a t t a c h e d top f l a n g e , i n t o t h e p r e s s u r e v e s s e l . When t h e f l a n g e i s f l u s h w i t h t h e t o p t h e c r u c i b l e i s a t t h e p r o p e r p o s i t i o n i n t h e s o l d e r b a t h which i s prehea ted t o 320'C. t h e f lange i s s e a l e d and t h e v e s s e l evacuated . The v e s s e l i s p r e s s u r i z e d w i t h t h e d e s i r e d g a s and, a s soon as t h e s o l d e r Pot tempera ture r e c o v e r s t o 32OoC, t h e run i s begun.

A f t e r lowering,

The sample i s hea ted a t a Cons tan t r a t e , normally 3OC/min, and t h e r o t a - t i o n of t h e r a b b l e arm s t i r r e r i s c o n s t a n t l y monitored and i s p r i n t e d out e a c h minute . The u n i t o f d i a l d i v i s i o n s p e r minute (DDPM) which is a c t u a l l y 100 times t h e r o t a t i o n a l speed i n RPM a r e t h e s t a n d a r d G i e s e l e r f l u i d i t y u n i t s .

A s t h e c o a l sample i s hea ted it b e g i n s t o s o f t e n and t h e stirrer b e g i n s t o r o t a t e . The p o i n t a t which t h i s o c c u r s i s c a l l e d t h e s o f t e n i n g tempera ture , Ts. F u r t h e r hea t ing t h e sample l e a d s t o a n i n c r e a s e of t h e s t i r r e r r o t a t i o n u n t i l t h e maximum r a t e i s reached a t t h e t e m p e r a t u r e of maximum f l u i d i t y , TM. F i n a l l y a s t h e tempera ture of t h e c o a l i s r a i s e d p a s t TM t h e f l u i d i t y b e g i n s t o d e c r e a s e u n t i l t h e tempera ture o f r e s o l i d i f i c a t i o n , TR, i s reached . A t t h i s p o i n t a l l s t i r r e r r o t a t i o n s t o p s and t h e sample i s normally f u l l y coked.

A t t h e end of a run t h e v e s s e l is d e p r e s s u r i z e d and t h e sample, c r u c i b l e and head assembly are removed f o r c l e a n i n g . hours .

R e s u l t s and D i s c u s s i o n

A complete run r e q u i r e s about 1.5-2

The c o a l used i n t h i s work was from Montour No. 1 mine and i s a h i g h v o l a t i l e , h i g h l y c a k i n g E a s t e r n U.S . b i tuminous c o a l from t h e P i t t s b u r g h No. 8 seam. The r u n of mine (ROM) c o a l was screened a t 3/4" and only t h e washed +3/4" lumps were used i n t h i s work. The c o a l was s t o r e d i n a sea led p l a s t i c bag and was ground f o r t h e G i e s e l e r work j u s t p r i o r t o use. Table 1 shows the proximate and u l t i m a t e a n a l y s e s of t h i s c o a l t o g e t h e r w i t h t h e energy c o n t e n t , t h e s tandard G i e s e l e r f l u i d i t y and F r e e Swel l ing Index (FSI) .

A t o t a l o f 44 r u n s were made i n t h i s s tudy , 2 3 with p r e p u r i f i e d n i t r o g e n and 21 with hydrogen. The r e s u l t s of t h e s e exper iments a r e g i v e n i n Table 2. The f l u i d i t y g i v e n a t e a c h p o i n t is t h e a v e r a g e of t h e maximum f l u i d i t y v a l u e from a t least two r u n s and f o r the u n p r e s s u r i z e d c a s e s , f o u r r u n s . The agreement between d u p l i c a t e r u n s was a lways b e t t e r t h a n i 10%.

S i n c e the maximum f l u i d i t y o b t a i n a b l e a t s t a n d a r d G i e s e l e r c o n d i t i o n s Of

1 . 4 0 o z - i n (141 gm.cm) o f t o r q u e i s about 28,000 most o f t h e d a t a obta ined here were a t l o w e r t o r q u e s e t t i n g s o f e i t h e r 0.45 o z - i n (45 g-cm) or 0.30 o z . i n (30 g-cm). A l l t h e d a t a r e p o r t e d i n t e r m s o f t h e s tandard t o r q u e va lue . This v a l u e was o b t a i n e d by m u l t i p l y i n g t h e measured f l u i d i t y by the r a t i o of s tandard t o r q u e t o t h e torque v a l u e a c t u a l l y used ( i . e . , 3.11 or 4 . 6 7 f o r t h e t w o c a s e s i n t h i s work). When d u p l i c a t e r u n s were made u s i n g the d i f f e r e n t t o r q u e s e t t i n g s t h e agreement between t h e c o r r e c t e d f l u i d i t i e s was a s good a s t h a t ob ta ined for d u p l i c a t e r u n s a t t h e same t o r q u e s e t t i n g . T h i s s u g g e s t s t h a t , a t l e a s t i n t h e c a s e of h i g h l y f l u i d coals, a c o a l i n i t s p l a s t i c s t a t e may resemble a Newtonian 1 i q u i d .

I f it is p o s s i b l e t o t r e a t t h i s c o a l a s a Newtonian l i q u i d we can , by c a l i b r a t i o n of o u r p l a s t o m e t e r c r u c i b l e and stirrer w i t h v i s c o s i t y s t a n d a r d s , e s t i m a t e t h e v i s c o s i t y o f t h e c o a l i n i t s p l a s t i c s t a t e . Such c a l i b r a t i o n g i v e s

168

t h e f o l l o w i n g r e l a t i o n s h i p between "pseudo" v i s c o s i t y , (po ise) and f l u i d i t y , F (DDPM) .

l o g i o Q = - l o g l o F + 7.257 1)

T h i s s u g g e s t s t h a t t h e apparent v i s c o s i t y o f t h e Montour N o . 4 c o a l used i n t h i s work, a t t h e tempera ture of i t s maximum f l u i d i t y , l i e s between about 170 and ZOO0 p o i s e .

F igure 3, a p l o t o f t h e d a t a i n Table 2 c l e a r l y shows t h e e f f e c t t h a t p r e s s u r e h a s on t h e maximum f l u i d i t y o f t h i s p a r t i c u l a r c o a l . I n i t i a l l y , t h e f l u i d i t y i s increased q u i t e r a p i d l y by r a i s i n g t h e p r e s s u r e o f b o t h hydrogen and n i t r o g e n , however, whi le t h e e f f e c t i s seen t o c o n t i n u e almost l i n e a r l y for t h e hydrogen p r e s s u r e , t h e n i t r o g e n p r e s s u r e h a s only a l i m i t e d e f f e c t above about 100 p s i g . who made a s i m i l a r s tudy f o r t h e medium f l u i d i t y , weakly caking Akabira c o a l . The i n i t i a l l a r g e i n c r e a s e i n maximum f l u i d i t y w i t h p r e s s u r e i s probably due t o t h e r e t a r d e d r a t e of v o l a t i l e e v o l u t i o n . With t h e more v o l a t i l e and hence presumably l e s s v i s c o u s components he ld i n t h e " p l a s t i c " c o a l l o n g e r , an i n c r e a s e i n maximum f l u i d i t y i s l o g i c a l .

These e f f o r t s a r e c o n s i s t e n t w i t h those observed by Kaiho and Toda(')

Another , a l t h o u g h seemingly l e s s l i k e l y , p o s s i b i l i t y f o r t h e i n c r e a s e d f l u i d i t y is t h e i n c r e a s e d d i s s o l u t i o n of t h e g a s used and/or c o a l g a s e s i n t h e c o a l l i q u i d s which may l e a d t o a d e c r e a s e i n t h e v i s c o s i t y of t h e c o a l system and hence t o a n i n c r e a s e i n t h e f l u i d i t y . The h i g h e r f l u i d i t i e s observed w i t h n i t r o g e n vs . hydrogen i n t h e range 0-150 p s i g may be a n exper imenta l a r t i f a c t caused by s l i g h t l y lower h e a t i n g r a t e s f o r t h e hydrogen c a s e s due t o t h e h igher thermal c o n d u c t i v i t y of hydrogen. I t is known t h a t h e a t i n g r a t e i s d i r e c t l y r e l a t e d t o t h e f l u i d i t y of c e r t a i n c o a l s . ( 3 )

A s t h e p r e s s u r e of t h e i n e r t g a s , n i t r o g e n , i s f u r t h e r i n c r e a s e d , t h e l e v e l i n g o f f of t h e f l u i d i t y may be due t o approaching t h e l i m i t s o f t h e e f f e c t of p r e s s u r e a l o n e on f l u i d i t y . P o s s i b l y p r e s s u r e s of 100-150 p s i g a r e s u f f i c i e n t t o r e t a r d t h e escape o f v o l a t i l e s u n t i l t h e p l a s t i c c o a l h a s reached i t s tempera ture of maximum f l u i d i t y . Above t h e s e p r e s s u r e s it a p p e a r s t h a t any a d d i t i o n a l v o l a - t i l e s which a r e t rapped have l i t t l e e f f e c t on t h e f l u i d i t y .

The much more d r a m a t i c e f f e c t of hydrogen p r e s s u r e on t h e maximum f l u i d i t y , F igure 3 , i s probably due t o r e a c t i o n s between t h e hydrogen and compo- n e n t s i n t h e c o a l a s w e l l a s t h e r e t a r d a t i o n of v o l a t i l e escape . T h i s observed hydrogen e f f e c t i s , of c o u r s e , c o n s i s t e n t w i t h t h e l i q u e f a c t i o n of c o a l by v e r y h igh p r e s s u r e s e 2000 p s i g ) of hydrogen a t approximately t h e t e m p e r a t u r e of maximum f l u i d i t y .

While t h e p r e s s u r e h a s a major e f f e c t on t h e maximum f l u i d i t y o f t h e c o a l it shows almost no r e l a t i o n t o t h e tempera ture of maximum f l u i d i t y . A l s o no e f f e c t of p r e s s u r e on t h e s o f t e n i n g p o i n t or t h e r e s o l i d i f i c a t i o n tempera ture was observed. Throughout t h i s work t h e s o f t e n i n g tempera ture was 360 &5OC, t h e s o l i d i f i c a t i o n tempera ture was 475 * 5OC and t h e tempera ture of maximum f l u i d i t y was 435 i 5OC.

REFERENCES

1 . Standard Method of T e s t f o r P l a s t i c P r o p e r t i e s of Coal by t h e Constant-Torque

2 . Kaiho, M . and Toda, Y . , Change i n t h e Thermoplas t ic P r o p e r t i e s of Coal Under

G i e s e l e r P l a s t o m e t e r . ASTM Designat ion: D 2639-71.

P r e s s u r e of Var ious Gases . 58 , 397 (May, 1979).

S t r u c t u r e s and P r o p e r t i e s of Coal I V I - - P l a s t i c Behavior on Heat ing ," F u e l 35, 462 (1955).

169

3 . Van Krevelen , D. W., Hunt jens , F. J . , and Dormans, H. N . M . , "Chemical

Prox ima te A n a l y s i s M O I S t U r e Ash V o l a t i l e M a t t e r

TABLE 1, - A n a l y s i s Of Montour NO. 4 Coal

U l t i m a t e A n a l y s i s (Dry Basis) C (8) H (8) N (%) s (8) 0 (BY D i f f . ) (%)

U l t i m a t e A n a l y s i s (MAF) C (8 ) H (%) N (%I s (B) 0 (By D i f f . ) (k,

Energy Con ten t (Dry B a s i s ) HW (BLu/lb)

F r e e S w e l l i n g Index

F l u i d i t y (DDPM)

1.69 6 .97

38 .79

76.81 5.16 1 . 7 3 1.35 7 .98

82.67 5.55 1 .86 1 .46 8 .46

14 .110

7-1/2

9300

TABLE 2 - F l u i d i t y o f Montour NO. 4 C o a l i n Ni t rogen and Hydrogen Atmospheres

Cas

N i t r o g e n

Hydrogen

p r e s s u r e (psig)

0 50

100 150 200 250 300 350 400

0 50

100 1 5 0 200 250 300 350 400

9,300 22 .300 38 ,800 44 ,600 46 .800 48 ,100

51.200 51.900

49.100

9 ,400 19.400 34 ,700 40,w0 51.100 65,900 80.800 95,100

1 0 4 , 9 0 0

(1) F l U i d i t y rounded to n e a r e s t 103 DDPM based on average of a t l e a s t 2 mea Nrement 9.

A l l runs a t 3 * . l °C/nin h e a t i n g r a t e .

170

1 L

171

DIFFUSION OF I O N S I N T O COAL: METHOD OF MEASUREMENT, ORDER OF MAGNITUDE AND DIRECTIONAL EFFECTS

By: A t t a r , A. and Warren, 0. Dept. Chem. Eng., N.C.S.U., Raleigh, N.C. 27650

1. INTRODUCTION Inco rpo ra t i on o f meta l i ons from s o l u t i o n i n t o the coal s t r u c t u r e

I n t h i s work, p r e l i m i n a r y

i s becaning a use fu l method t o achieve h i g h con tac t between the coal sur face and the meta l i ons . However, no data were found i n the l i t e r a t u r e r e l a t i v e t o the d i f f u s i v i t y o f i ons i n coa l . r e s u l t s are repo r ted on t h e r a t e o f d i f f u s i o n o f ions i n t o coal and on t h e r a t e o f leaching o f i o n s from coal .

The main r e s u l t s found are t h a t : i n d i f f e r e n t d i r e c t i o n s o f a v i t r i n i t e p a r t i c l e , r e l a t i v e t o the d i r e c t i o n o f t h e beddin and 2) t he d i f f u s i o n c o e f f i c i e n t o f calcium i o i s o f t h e o rde r o f lO- l~ 'cm2/sec i n the d i r e c t i o n o f the bedding and i n the d i r e c t i o n pe rpend icu la r t o the bedding.

i n polymethyl me tac ry la te stubs, 3/4" i n diameter and 3/8 - 1/2" t h i c k . The s tubs were c u t through t h e c o a l p a r t i c l e s and the exposed sur faces were p o l i s h e d under pet ro leum e t h e r , us ing c l o t h s 220, 400 and 600 success ive ly . F i n i s h i n g was done u s i n g 0.3 micron alumina powder i n petroleum e the r . The p o l i s h e d sur face was s p u t t e r e d w i t h carbon and grounded w i t h s i l v e r p a i n t .

The sur faces were scanned us ing a 20000 V o l t e l e c t r o n beam and the K, x-rays f r a n the ca lc ium were c o l l e c t e d w i t h i n + 2 eV. The r e s o l u t i o n between the Ca (b) l i n e s and the K (Kg) l i n e s appears t o be adequate t o a l l o w separat ion o f t h e calcium.

Scanning o f t he coa l sur face was done a t t h e r a t e o f 3 microns/minute and p l o t t e d a t e i t h e r 3 microns/ inch o r 16 microns/inch. o f x-rays were i n t e g r a t e d and p r i n t e d every 20 seconds.

3. MODES OF CALCIUM PENETRATION

o f a tans o f ca lc ium i n a segment o f volume o f t he coal specimen, w i t h a shape o f a d r o p l e t o f t e a r , with an average l e n g t h o f about 6-10 microns and a diameter o f 3-5 microns near the surface. This volume w i l l be here- t o f o r e t i t l e d the "probe volume." Obviously, t he s igna l obtained w i l l n o t reso lve d i f f e rences i n concentrat ions o f ca lc ium associated w i t h fea tu res sma l le r than the probe volume and consequently t h e s i g n a l i s on l y an average measure o f t h e ca lc ium p resen t i n the probe volume i n a l l forms. A s p e c i a l mathematical method i s being developed t o "deconvolute" the s i g n a l i n order t o reso lve f i n e r fea tu res .

1) the d i f f u s i v i t y o f ions va r ies

cm2/sec

2 . EXPERIMENTAL The coa l p a r t i c l e s t o be examined were h o t pressed (7OoC, 15000 p s i )

The t o t a l counts

The r e s u l t s t h a t a re obta ined a re a s i g n a l p ropor t i ona l t o t h e number

The main modes by which ca lc ium cou ld have penetrated i n t o t h e coa l are 1. Pene t ra t i on o f Cat2 through pores. 2 . D i f f u s i o n o f Ca+2 ions i n t o t h e s o l i d m a t r i x and forming a Ca-

con ta in ing i n t e r c o l a t e . F igure 1 shows the form o f t he s i g n a l expected when pene t ra t i on o f Ca occurs i n t o t h e s o l i d , through a pore o r i e n t e d p a r a l l e l t o the d i r e c t i o n o f t r a v e l of t h e beam and through a pore presented perpendicu lar t o the d i r e c t i o n o f t r a v e l of t h e beam. Since the d i f f u s i o n c o e f f i c i e n t i n l i q u i d i s substan- t i a l l y l a r g e r than i n s o l i d , a r e l a t i v e l y l o w i nco rpo ra t i on occurs v i a t h e micropores (r < 0.01 M ) and most o f t he ca lc ium inco rpo ra t i on occurs v i a the mesopores and t h e macropores.

F i r s t , the models and t h e i r s o l u t i o n s w i l l be described and then data w i l l be presented and i n t e r p r e t e d .

Several models can be used t o i n t e r p r e t t he experimental r e s u l t s .

.. . 172

3.1

Thus :

E f f e c t i v e D i f f u s i o n through a Thin Layer o f S o l i d I n t h e case o f a t h i n l a y e r the u n i d i r e c t i o n a l model i s app l i cab le .

a c = a c a t 2 9

2 (1 1 -

c(0,x) = 0 y

c(t,O) = co , and

The s o l u t i o n i s : c(t,-) = O .

X C = e r f c (-1 . cO 2 q

(5)

x i s the d i s tance from t h e sur face, OS i s t h e e f f e c t i v e d i f f u s i v i t y c o e f f i c i e n t , and t i s the pene t ra t i on time. i s c and co i s t h e concen t ra t i on near t h e sur face. canplementary, e r f c , i s def ined by:

The concen t ra t i on a t ( x , t ) The e r r o r f unc t i on

(6)

- _ & , a t L ,x2 c(D,t) = co , C(X,O) = 0 , ac - ( e , t ) = 0. ax

The s o l u t i o n i s : -xnDLt 2

m

s i n xnx - = C 1 - 1 4e cO n = l (2n-1)n + (-I)"++'

Obviously :

(7) m 2 J;; e-' du = 7 0

Equation (5) i s u s e f u l t o i n t e r p r e t data f o r d i f f u s i o n through a was used t o normal ize the d i s t r i b u t i o n s .

t h i n l a y e r o f s o l i d o r e f f e c t i v e d i f f u s i v i t y through heterogeneous fea tu res sma l le r than the depth o f penetrat ion. 3.2 E f f e c t i v e D i f f u s i o n Through a Pore F u l l w i t h L i q u i d

9

(8)

(9) (10)

(11)

(12)

(2n-1)n . A = n 2a. The t o t a l m a t e r i a l d i f f u s e d a f t e r t ime t i s : *

-A-D, t

d t 'n t t m e " M = - D(E) Adt + 4DAc0 1

0 x=o 0 n = l (2n-1)a .k (-1)"+' -XnDLt 2

m

= - 4DAc0 1 1 - e n = l ~ ( 2 n - l ) n + (-I)"+'] xnoL

173

The use of equation (14) i s not imnediately obvious since the to ta l area of pore mouth/unit mass, A , i s n o t readily available and because A n depends on the d is t r ibu t ion of pore lengths.

4. TESTS PERFORMED The experimental tests performed can be divided in to two classes: A . Tests used t o develop the method. B . Tests on samples exposed t o calcium acetate solution a t room

temperature and atmospheric pressures. 4.1 Method Development

The method t h a t h a s been developed was described i n the previous section. The poss ib i l i t y of inaccurate resu l t s due t o overlap of conse- q u a t i v e scanning in te rva ls should be addressed. Since the beam i s a b o u t 4 microns i n diameter and a p r i n t o u t i s generated every twenty seconds, each printout represents counts t a k e n over 4 microns diameter beam which moved 1 micron. T h u s , the second printout will include counts taken from some of the calcium atoms which contributed t o the f i r s t counts. I n addi- t i o n , since the electron beam damages the surface t o some exten t , the r e su l t s may be d is tor ted . The data show, however, t ha t in three Ca curves almost on the same coal surface p a t h , forward, backward and forward again, very l i t t l e d i s to r t ion occurred over about 200 microns. 4.2 Incorporation Tests

Colberg seam ( W . Va. ) were: Samples of v i t r i n i t e from an I l l i n o i s #6 (Monterey Mine) and of the

1 . Leached with HC1 2:l per 20 min. 2. Mixed with 0.05M calcium acetate solution a t room temperature

f o r 78 hours, dried and stored under nitrogen unt i l fixed in the polymer.

Leaching of calcium occurs through a boundary layer. The thickness of the leached layer i s d i f f e ren t in d i f fe ren t directions of the seam.

The r e su l t s on the HC1 treated samples had a large s t a t i s t i c a l e r ro r b u i l t i n to them b u t show tha t :

1 . 2.

For each leaching, the governing equation i s :

The data collected f o r the f i r s t fourteen microns near the surface and the background information a re tabulated in Table 1.

a l o t of x/(2m vs. x should give a s t r a igh t l i n e , with slope of l':;ih$ . T h e l i ne wi l l not necessarily in te rsec t with the or ig in , since there is uncertainty r e l a t ive t o the exact location of the surfac

In accord w i t h equation

of the par t ic le . Figure 2 shows tha t he lope of the l i ne i s 806.4 cm- t which

10- 18 cm 3 /sec since the leaching time was 78

values of De i n the range of 10-9 - 10- i! cm 5 /sec. However, i t appears

corresponds t o De = 1.68 hours. Similar calculations f o r scans d i f e r en t directions yielded

tha t 10-12 cm2/sec can be considered a representative number f o r t h i s coal. Many samples of coal were treated fo r periods of 1 hour t o 5 days

w i t h excess solution of 0.05M calcium acetate in water. The samples were fixed in polymethyl metacrylate base, sputtered with carbon and analyzed a s before. The data seem t o indicate two modes of penetration of calcium: ( A ) by diffusion through the surface, and ( b ) by f i l l i n g u p o f pores. Schematically, the calcium signal shows three types of behavior as the electron bean t rave ls from the outside of the par t ic le i n ( A ) gradual decrease in calcium concontration in accord with the diffusion through the sur face , i . e . , e r fc [x/(2m]; ( B ) large and reasonably fixed level of s igna l , corresponding t o scanning along a pore; and ( C ) a Gaussian-shaped peak, corresponding t o traveling across a pore.

1 7 4

Table 1. HC1 leached coa l

Distance f rom Coal Surface Counts c/c e r f (-) = - - 1 c X

(microns) co = ? l o co 2 9

-4 2 0.018 - -3 1 0.009 - -2 1 0.009 - -1 3 0.027 - 0 3 0.027 -

+1 10 0.091 0.091 2 12 0.019 0.098 3 13 0.118 0.105 4 20 0.182 0.163 5 36 0.327 0.298 6 47 0.427 0.398 7 52 0.473 0.447 8 69 0.627 0.630 9 74 0.673 0.695

10 71 0.645 0.654 11 77 0.700 0.738 I 12 86 0.782 0.873 13 73 0.664 0.863 14 96 0.873 1.085

The r e s u l t s o f scans o f a sample o f coa l from the Colberg seam, West V i r g i n i a , i n two orthogonal d i r e c t i o n s are descr ibed below. The data f o r t he f i r s t 21 microns a re g iven i n Tables 2 and 3. shows t h a t t h e pene t ra t i on i n t h e v e r t i c a l d i r e c t i o n i s much slower bu t more un i fo rm than pene t ra t i on i n the h o r i z o n t a l d i r e c t i o n . The e f f e c t i v e d i f f u s i v i t y co- e f f i c i e n t i n the v e r t i c a l d i r e c t i o n i s about two orders o f magnitude sma l le r than i n the h o r i z o n t a l d i r e c t i o n . Table 2. Scanning o f Colberg seam coa l i n t h e d i r e c t i o n o f t h e g r a i n Distance from Surface Counts v c o = l 973) e r f c - l (c)

(microns) cO

F igure

-2 1005 0.5094 - Coal -1 1019 0.5165 - P a r t i c l e -+ 0 1973 1 .oooo - Surface 1 1860 0.9427 0.051

2 1755 0.8899 0.099 3 1520 0.7704 0.208 4 1336 0.6771 0.294 5 1139 0.5773 0.398 6 941 0.4769 0.504 7 818 0.4146 0.574 8 725 0.3675 0.638 9 566 0.2869 0.755

10 591 0.2995 0.730 11 46 1 0.2336 0.841 12 442 I 0.2240 0.860 13 444 0.2250 0.858 14 424 0.2149 0.877

175

Table 3. Scanning o f Colberg seam coal perpendicu lar t o t h e d i r e c t i w o f t he g r a i n

-i c e r f c (r) Distance f rom Surface - C ( ~ ~ ~ 1 9 7 3 ) cO 0 (microns) Counts

~~ ~~

-21 60 0.1881 - -20 61 0.1912 - -19 74 0.2319 -18 61 0.1912 -17 71 0.2226 -16 80 0.2508 -1 5 93 0.2915 -1 4 80 0.2508 -1 3 106 0.3323 -1 2 141 0.4420 -1 1 166 0.9204 -10 166 0.5204 - 9 184 0.5768 - 8 217 0.6802 - 7 205 0.6426 - 6 253 0.7931 - 5 278 0.8715 - 4 271 0.8495 - 3 282 0.8840 - 2 260 0.8150 - 1 278 0.8715

0 319 1 .oooo 0.0000 1 264 0.8276 0.1580 2 281 0.7555 0.2210 3 301 0.9436 0.0510 4 262 0.8213 0.1590 5 238 0.7461 0.2280 6 234 0.7335 0.2480 7 235 0.7367 0.2481 8 223 0.6990 0.2750 9 2 09 0.6552 0.3150

10 239 0.7492 0.2280 1 1 232 0.7272 0.2460 12 209 0.6552 0.3150 13 175 0.5486 0.4310 1 4 221 0.6928 0.2790 15 202 0.6332 0.3380 16 224 0.7072 0.2750

5 . CONCLUSIONS The main o b j e c t i v e s o f t h i s s tudy were achieved: 1. A method has been developed which a l lows examination of t h e

p e n e t r a t i o n o f ca lc ium ions i n t o coa l . 2. The method was a p p l i e d t o study t h e pene t ra t i on o f calcium

i n t o coals. The data show t h a t ca lc ium penetrates i n t o coal i n two main modes:

v i a pores and v i a r e g u l a r d i f f u s i o n . The d i f f u s i v i t y c o e f f i c i e n t i n the h o r i z o n t a l d i r e c t i o n r e l a t i v e t o t h e seam i s 102 - 103 times l a r g e r than i n t h e v e r t i c a l d i r e c t i o n . un2/sec w h i l e i n t h e v e r t i c a l d i r e c t i o n i t i s o f t he order o f cmz/sec. obedding = 7.6.10-11 cm2/sec. Over t i ca l = 9.7.10'13 cmz/sec.

I n t h e h o r i z o n t a l d i r e c t i o n i t i s 10-8 - -

176

Flaurm 1

EFFECT OF DIFFERENT FEATURES

ON THE PROBE SIONAL

%... I

"CI ,*.e*.o C O A L 0.7. .*.L..,.

X

0..

0..

0..

9 e

x 0.I

I 0 I "I.....

1 7 7

E f f e c t o f Composi t ion on F r e e z i n g P o i n t s o f Model Hydrocarbon F u e l s

W . A . A f f e n s , J . M . H a l l , S . H o l t , R. N . H a z l e t t

Naval Resea rch L a b o r a t o r y , Washington, D . C . 20375

INTRODUCTION

F r e e z i n g P o i n t s o f Je t F u e l s

Jet a i r c r a f t a r e f r e q u e n t l y exposed t o l o w o p e r a t i n g tempera- t u r e s and it i s e s s e n t i a l t h a t t h e i r f u e l s n o t f r e e z e i n t h e s e envi ronments . P l u g g i n g of f i l t e r s , p u m p a b i l i t y , and r e l a t e d f u e l s y s t e m o p e r a t i o n a l problems are dependent on f r e e z i n g p o i n t , and fo r t h i s r e a s o n , j e t f u e l s p e c i f i c a t i o n s i n c l u d e r e q u i r e m e n t s f o r maximum f r e e z i n g p o i n t . Commercial j e t f u e l (Jet A , A v i a t i o n Tur- b i n e F u e l , ASTM D 1655-80) , f o r example, i s r e q u i r e d n o t t o f r e e z e above - 4 O O C . M i l i t a r y j e t f u e l s , b e c a u s e o f wor ld w i d e o p e r a t i o n s , have even lower t e n p e r a t u r e r e q u i r e m e n t s . The maximum a c c e p t a b l e f r e e z i n g p o i n t s f o r A i r F o r c e f u e l s (JP-4 and JP-8 A v i a t i o n T u r b i n e F u e l s , MIL-T-5624L and MIL-T-83133A r e s p e c t i v e l y ) a r e -58' and -5OOC; and t h e N a v y ' s JP-5, (MIL-T-5624L, High F l a s h P o i n t A v i a t i o n T u r b i n e F u e l ) has a maximum of -46OC.

The low t e m p e r a t u r e p r o p e r t i e s o f a j e t f u e l ( f r e e z i n g p o i n t , pour p o i n t , v i s c o s i t y ) , as w e l l a s some o f i t s o t h e r p r o p e r t i e s , are c o n t r o l l e d b y t h e n a t u r e and c o n c e n t r a t i o n s of i t s components (chemi- c a l c o m p o s i t i o n ) . U n f o r t u n a t e l y , many components o f a f u e l which t e n d t o l o w e r f r e e z i n g p o i n t ( s m a l l e r hydrocarbons o f h i g h e r vapor p r e s s u r e ) , w i l l a l s o l o w e r t he f l a s h p o i n t . I n t h e case of JP-5, b e c a u s e o f i t s r e l a t i v e l y h i g h minimum r e q u i r e m e n t f o r f l a s h p o i n t (6OOC) f o r reasons o f s h i p s a f e t y , and i t s l o w maximum r e q u i r e m e n t fo r f r e e z i n g p o i n t (-46OC), i t i s n o t a lways p r a c t i c a l t o produce JP-5 from a l l a v a i l a b l e c r u d e s . These r e s t r a i n t s l i m i t t h e amount of JP-5 which c a n b e produced from a b a r r e l o f c r u d e o i l and t he problem e x i s t s f o r b o t h c o n v e n t i o n a l JP-5 ( f rom p e t r o l e u m ) and f o r JP-5 f rom syncrudes .

F r e e z i n g P o i n t and Composi t ion

I t h a s been known t h a t m o l e c u l a r s i z e and symmetry p l a y a n i m p o r t a n t par t i n t he phenomenon o f c r y s t a l l i z a t i o n from s o l u t i o n and t h a t t h i s a l s o a p p l i e s t o s o l u t i o n s o f hydrocarbons . D i m i t r o f f e t a 1 ( 1 , 2 ) , s t u d y i n g t h e e f f e c t o f c o m p o s i t i o n on several t y p e s o f f u e l s , found t h a t t he s a t u r a t e f r a c t i o n e x e r t e d t h e g r e a t e s t i n f l u e n c e on r a i s i n g the f r e e z i n g p o i n t and t h a t t h e p r e s e n c e and amount of h igh - t empera tu re f r e e z i n g hydroca rbons had a major i n f l u e n c e . They r e p o r t e d t h a t i n some cases t h e aromatic f r a c t i o n was i m p o r t a n t and t h a t i n g e n e r a l a l l hydrocarbons p l a y a p a r t i n f u e l c r y s t a l l i z a t i o n . P e t r o v i c and Vitorovic ( 3 ) found a correla- t i o n between t h e sum o f t h e c o n c e n t r a t i o n s o f t h e t h r e e l a r g e s t s t r a i g h t c h a i n a l k a n e s and f r e e z i n g p o i n t i n t h e j e t f u e l s which t h e y s t u d i e d . Anto ine r e p o r t e d on s t u d i e s o f 32 samples of j e t

178

fuel derived from oil shale and coal syncrudes (4) and conclude& that the concentrations of the long straight chain molecules in the fuels exert influence on the freezing point but are not the complete controlling factor. Solash et a1 ( 5 ) at this laboratory investigated jet fuels derived from various sources and reported that the freezing points were related to the amount of the largest ;-alkane present (but not the total n-alkane concentration) in these fuels. These findings were not in agreement with the correlation of Petrovic and Vitorovic. Solash et a1 plotted log (mol% C ) vs. the reciprocal freezing point of 11 fuels and found reasonakfe adherence to a solubility plot. They concluded that the freezing point of a fuel is not a simple function of fuel composition and that much more work must be done before a coherent theory of freezing point can be developed for multi-component mixtures.

It was decided to extend our freezing point studies to model hydrocarbon fuel mixtures, with emphasis on the higher ;-alkanes, in order to learn more concerning the effect of composition on freezing point.

EXPERIMENTAL

Defining Freezing Point

"Freezing Point," as applied to jet fuels and related mixtures, is defined by the ASTM (6) as "..that temperature at which crystals of hydrocarbons formed on cooling disappear when the temperature of the fuel is allowed to rise". This, of course, is really a "melting point," since "freezing point" is the temperature at which crystals start to crystallize out. However, the two phenomena take place at almost equivalent temperatures, and the term "freezing point" will be used here because of its wide use in the fuel literature.

Determination of Freezing Point

Freezing points were determined by the ASTM method D2386 for aviation fuels ( 7 ) with some modifications. Temperature readings were made by means of a thermocouple (Type "J") - potentiometer- recorder system, and liquid nitrogen was used as the refrigerant. Stirring was done mechanically.

Hydrocarbons

The hydrocarbons used were 99% pure grade. The decalin (deca- hydronaphthalene) was found to consist of 62.7% (w/w) of the trans isomer and 3 7 . 3 % cis isomer by gas chromatography. The "Isopar-M" kerosene consisted of a relatively high boiling, low freezing, narrow-cut isoparaffinic solvent whose average molecular weight was 191 (8).

179


n-Alkanes i n Isopar-M

c o n c e n t r a t i o n s (mol % ) were p repa rhz a n d l z h e i r f r e e z i n g p o i n t s (T,) d e t e r m i n e d . R e c i p r o c a l f r e e z i n g p o i n t s (1 /T v s l o g of concen- t r a t i o n s are p l o t t e d i n F i g u r e 1 f o r each a l g a n e . scale ( o r d i n a t e ) o f t h e g r a p h i s r e v e r s e d i n o r d e r t o show tempera- t u r e i n c r e a s e go ing up t h e graph . I t i s seen i n t h e f i g u r e t h a t t h e d a t a p o i n t s f i t t h e s t r a i g h t l i n e s f a i r l y w e l l so t h a t t h e r e i s good adhe rence t o a t y p i c a l s o l u b i l i t y p l o t ( i d e a l f r e e z i n g p o i n t c u r v e ) . The l i n e s shown i n t h e g raph w e r e d e r i v e d by means of a l i n e a r r e g r e s s i o n t r e a t m e n t of t h e d a t a and are a b e s t f i t o f t h e d a t a . From t h e i r s l o p e s and i n t e r c e p t s , h e a t s (AH ) and e n t r o p i e s (ASm) o f f u s i o n and e x t r a p o l a t e d f r e e z i n g p o i n t s p u r e a l k a n e s w e r e c a l c u l a t e d by means of t h e V a n ' t Hof? i d e a l s o l u - b i l i t y e q u a t i o n ( 9 - 1 2 ) , and t h e thermodynamic r e l a t i o n s h i p between ASm, AHm and T ( 1 3 ) .

S o l u t i o n s of s i x n-a lkanes ( C - C ) i n Isopar-M a t v a r i o u s

The t e m p e r a t u r e

YT, ) of t h e

m,o

Ln X = - AHm/RTm + AHm/RTm,o

where R i s t h e g a s c o n s t a n t , and X r e p r e s e n t s molar c o n c e n t r a t i o n . This approx ima te e q u a t i o n , which d e s c r i b e s t h e v a r i a t i o n of f r e e z i n g p o i n t w i t h c o n c e n t r a t i o n , i s based on s e v e r a l s i m p l i f y i n g a s sumpt ions i n c l u d i n g t h a t AHm i s independen t of t e m p e r a t u r e , and t h a t R a o u l t ' s l a w i s obeyed . Der ived f r e e z i n g p o i n t d a t a from t h e Isopar-M s o l u - t i o n s a r e shown i n Table I wi th l i t e r a t u r e v a l u e s of p u r e n -a lkanes ( 1 3 , 14) shown f o r compar i son .

I t is s e e n i n t h e t a b l e t h a t t h e e x p e r i m e n t a l l y d e r i v e d and l i t e r a t u r e Tm v a l u e s are i n good agreement , b u t t h i s i s n o t a lways t h e case f o r r o A H and AS . F o r AH and AS,, t h e agreement is good o n l y fo r t h e even g a r b o n n%bered a l p a n e s , b u t t h e r e i s poor a g r e e - ment f o r t h e odd numbered compounds. I t h a s long been known ( 9 ) t h a t f r e e z i n g and m e l t i n g p o i n t d a t a of p u r e compounds i n some homologous series o f t e n e x h i b i t t h e phenomenon o f " a l t e r n a t i o n " . I n t h e s e series, such as t h e " -a lkanes , w i t h each a d d i t i o n a l CH2 g roup , a l t e r - n a t e l y sma l l and l a r g e i n c r e a s e s i n a g i v e n p r o p e r t y are obse rved ( 9 ) . T h i s c a n be s e e n f o r each of t h e t h r e e p r o p e r t i e s i n Tab le I f o r b o t h t he l i t e r a t u r e d a t a f o r t h e p u r e a l k a n e s , and t h e v a l u e s d e r i v e d from the Isopar-M s o l u t i o n f r e e z i n g p o i n t s . I t h a s been shown ( 9 ) f o r t h e h i g h e r members of a homologous s e r i e s , t h a t AHm and ASm v a l u e s f a l l on t w o l i n e a r c u r v e s when p l o t t e d a g a i n s t ca rbon number. I n t h i s work, t h e odd and t h e even carbon numbered a l k a n e d a t a a l s o form two s e p a r a t e s t r a i g h t l i n e s r e s p e c t i v e l y when AHm o r ASm are p l o t t e d a g a i n s t carbon number. The re was , however, a much wider v a r i a t i o n be tween t h e odd and even d a t a p o i n t s f o r t h e l i t e r a t u r e v a l u e s than be tween t h a t o f t h e e x p e r i m e n t a l l y d e r i v e d p o i n t s i n t h i s s t u d y .

180

solvent Effect_

In a second set of freezing point experiments, the effect of solvent was investigated. Solutions were prepared for 5-tetradecane, 1-hexadecane, and naphthalene in different solvents and at several concentrations. In the case of n-hexadecane, some mixed solvents were also used and their compositions are shown in Table 11. Freez- ing point data were plotted in the same manner as that of the alkanes in Isopar-M. Some of the n-hexadecane data for single solvents are shown in Figure 2. It is seen in the figure that the straight lines plotted fit the data fairly well for these four plots and this was also true for the other solutions. The solvent effect experimental data (Tm and X) were also treated by linear regression and the derived freezing point data are shown in Table 111. For each of the three solutes, the solvents are listed in order of increasing AH,. Literature data ( 1 3 , 1 4 ) for the pure solutes are included in the table for comparison. An examination of Figure 2 and Table I11 shows considerable variation in the derived data for each of the solutes in the different solvents. When a solid dissolves in a liquid and an ideal solution is formed, the process may be considered equivalent to melting of the pure solute at the lowered temperature at which solution is taking place, and the ideal solubility equation implies this concept (9-12). From the ideal solubility equation (or from the solubility plots in Figures 1 and 2 ) , it follows that relative solubility bears an inverse relationship with Tm. At a given concentration, for a relatively good solvent, solution (melting) will take place at a lower temperature than that of a relatively poorer solvent. Similarly, at a given temperature, it can be shown that solubility increases with decreasing AH for systems which obey the ideal solubility equation. In generaf, both Tm and AHm are approximate measures of relative solubility. For exdmple, in Figure 2 , it is seen that decalin (the lowest curve in the figure) is a relatively better solvent for E-hexadecane than secondary butyl benzene (the upper curve). The data in Table I11 also illustrate this concept. For C14, in the three solvents shown in the table, n-heptane and Isopar-M are good solvents, and secondary butyl benzene, an aromatic compound, the poorest. The Tm tufe value'for the pure C14 ( 2 7 9 ' K ) within experimental error. C16 in individual solvents, n-heptane, decalin and Isopar-M appear to be relatively good solvents, and secondary butyl benzene the poorest. The Tm values derived for decalin ( 2 8 9 ' K ) and Isopar-M (290 'K) solution6 are the same as that of pure C16 within experimental error, but the E-heptane result ( 2 9 5 ' K ) seems to be high.

in mixed solvents, Solutions A, B and C are relatively good

for C in Isopar-M (280 'K) is the same as that of the litera- For

s , and Solution G the poorest. As seen in Table 11, Solutions A, B and C consist chiefly of Isopar-M or Isopar-M and decalin which were shown above to be relatively good solvents for C16. the aromatic (Solution G ) was the poorest. For naphthalene, as might be expected, Table I11 shows that secondary butyl benzene is a better solvent than Isopar-M. butyl benzene solutions ( 3 7 4 ' K ) , howeveriois much higher than that of pure naphthalene ( 3 5 4 ' K ) . The naphthalene data are limited, however, to only two solvents at a limited number of concentrations.

Again, I

The Tm derived from the secondary I I

I , ,

181

T e r t i a r y S o l u t i o n s

I n o r d e r t o o b s e r v e p o s s i b l e i n t e r a c t i o n between E-a lkanes i n a common s o l v e n t and i t s e f f e c t on f r e e z i n g p o i n t , s o l u t i o n s o f "--C13 and n-C i n Isopar-M were p r e p a r e d a t s e v e r a l c o n c e n t r a t i o n s . S t a n x a r A 6 f r e e z i n g p o i n t p l o t s of 1 /~ , v s . Log E-c a t s e v e r a l con- s t a n t C &!e 0 % C16 l i n e i n t h e grab8 i s t h e c u r v e f o r C s e e n i n t h e f i g u r e t h a t t h e b.17% C16 d a t a p o i n t s f a l l on a p a r a l l e l s t r a i g h t l i n e , b u t a t somewhat lower t e m p e r a t u r e s t h a n t h a t of t h e pure,C13 l i n e . However, a change i s obse rved f o r h i g h e r C16 concen- t r a t i o n s . The 0 .42% C c u r v e c o n s i s t s of two l i n e s o f o p p o s i t e s l o p e s . 0 . 1 7 % C The 0 .84% and 1.69%,C16 d a t a f o l l o w t h e p a t t e r n of t h e 0.4$@ C1 The 4 .25% C16 l i n e i s h o r i z o n t a f , showing t h a t changes i n C e f f e c t , and t h a t t h e C16 h a s " t aken o v e r L 3 t h e c o n t r o l of f r e e z i n g p o i n t .

c o n c e n t r a t i o n s are shown i n F i g u r e 3 . i n Isopar-14 from F i g u r e 1. I t i s

The s e c t i o n o*6 the c u r v e above a b o u t 3 % C13 f a l l s on t h e l i n e .

c u r v e b u t w i t h d e c r e a s i n g s l o p e s . c o n c e n t r a t i o n have no

Two i n t e r e s t i n g o b s e r v a t i o n s were n o t e d i n F i g u r e 3. F i r s t , f o r c o n c e n t r a t i o n s of 0 . 4 2 , 0 .84 , and 1 .69% C , a d d i t i o n of C13 a t k g lower C c o n c e n t r a t i o n s c a u s e s a r e d u c t i b g of f r e e z i n g p o i n t .

The second A J s e r v a t i o n , which was unexpec ted , i s t h a t c e r t a i n com- b i n a t i o n s o f C13and C16 i n Isopar-M f r e e z e a t l o w e r t e m p e r a t u r e s t h a n t h a t o f t h e same c o n c e n t r a t i o n of e i t h e r a l k a n e a l o n e i n t h e same Isopar-M b a s e s t o c k . F o r example, t h e f r e e z i n g p o i n t of 1 .04% C and 0.17% C i n Isopar-M w a s 207 'K, whereas t h e f r e e z i n g p o i n t A? 1 . 0 4 % C 225OK. '2 s i h f l a r s o l u t i o n of 3.11% C13 + 0 . 4 2 % C whereas t h e f r e e z i n g p o i n t s o f t h e s i n g l e alkanes'gn Isopar-M were 2 2 1 ° K and 233 'K r e s p e c t i v e l y f o r 3.11% C13 and 0.42% C16.

The d a t a i n F i g u r e 3 s u g g e s t t h a t t h e r e h a s been i n t e r a c t i o n between t h e C and C i n t h e i r mutua l i n f l u e n c e on t h e f r e e z i n g p o i n t s i n IsohAr-M s o l g t i o n s .

( E 6 = 0 ) w a s 209OK and t h a t of 0 . 1 7 % C16 (C13 = 0 ) was f r o z e a t 218OK,

The f r e e z i n g p o i n t - c o n c e n t r a t i o n p l o t s f o r C13 and C16 , in Isopar-M ( F i g u r e 1) show r e l a t i v e l y c l o s e adhe rence t o t h e i d e a l s o l u b i l i t y e q u a t i o n s u g g e s t i n g a minimum of i n t e r a c t i o n between t h e i n d i v i d u a l s o l u t e s and s o l v e n t for e i t h e r a l k a n e . B u t , when t o g e t h e r i n t h e s a m e s o l u t i o n , t h e i r mutua l b e h a v i o r i s unexpec ted . The mutua l s o l u b i l i t y of t w o compounds i s a q u a l i t a t i v e measure o f t h e e x t e n t of t h e i n t e r a c t i o n between t h e i r m o l e c u l e s , v a r y i n g from s i m p l e d e p a r t u r e from i d e a l b e h a v i o r t o a c t u a l compound fo rma t ion between t h e two s u b s t a n c e s ( 1 2 ) . I n some c a s e s , it i s p o s s i b l e t o e x p l a i n d e v i a t i o n s f rom i d e a l i t y . Most commonly, t h e e x p l a n a t i o n i s based on a s s o c i a t i o n t o form d imers o r trimers; compound fo rma t ion between s o l u t e and s o l v e n t ; o r p o s s i b l y d i s s o c a t i o n o f t h e s o l u t e t o f o r m two o r more m o l e c u l e s (11). The l a s t o f t h e s e p o s s i b l e e x p l a n a t i o n s ( d i s s o c i a t i o n ) , however, would n o t be expec ted t o a p p l y t o s o l u t i o n s of a l k a n e s i n hydrocarbon s o l v e n t s . Another p o s s i b l e e x p l a n a t i o n i s t h a t t h e two a l k a n e s form a e u t e c t i c t y p e m i x t u r e . I n t h e c a s e of t h e C13-C16 i n Isopar-M b e h a v i o r , t h i s i s now under i n v e s t i g a t i o n . I t i s hoped t h a t by i s o l a t i n g t h e c r y s t a l s which f o r m d u r i n g f r e e z i n g , a n d i d e n t i f y i n g them, an e x p l a n a t i o n o f t h i s b e h a v i o r migh t be fo r thcoming . T h i s work i s s t i l l i n p r o g r e s s .

18 2

SUMMARY AND CONCLUSIONS

A study was made of the effect of composition on the freezing points of model hydrocarbon jet fuel type mixtures. Solutions of higher n-alkanes (C - C ) in several solvents were emphasized. Freezing points (T f20f s&lutions of single alkanes were found to conform with the S n ' t Hoff ideal solubility equation. slopes and intercepts of plots of concentration (Ln X) vs l/Tm, heats ( A H ) and entropies (AS ) of fusion, and extrapolated freezing points ofmpure alkanes (T )mwere derived. For an isoparaffinic base solvent (Isopar-M), TI58 derived T values were in good agreement with the literature values for thZ'3ure alkanes. ASm,,only the even carbon numbered alkanes exhibited values similar to literature data for the pure compounds. This alternating behavior for the n-alkanes series has been observed for melting point and other properties of the pure compounds. other solvents, considerable solubility effect was noticed. For

and C 6, decalin and Isopar-M were found to be relatively good %!vents But aromatic compounds, such as butyl benzenes, were relatively poor. For naphthalene, butyl benzene was a better solvent than Isopar-M. ficant changes or reversals of slope were observed for 1/T plotted against Ln X (C13 concentration) at various C concentrations, and this suggested interaction between the two a d h e solutes. C had the predominant effect in C13 + C16 solutions in Isopar-M. about 4 % C16, changes in C13 concentration had no observable effect.

From the

For AHm and

For alkanes in

For mixtures of C13 and C16 in Isopar-M, signi-

Ahhe

REFERENCES

1. Dimitroff, E., Gray, Jr., J. T., Meckel, N. T., and Quillian. Jr., R. D., 7th World Petroleum Congress, Mexico City, April 1967, Individual Paper NO. 47.

2. Dimitroff, E. and Dietzman, H. E., American Chemical Society, Petroleum Division, Preprints, 14, B-132 (1969).

3 . Petrovic, K. and Vitorovic, D., J. Inst. Pet. 59, 20 (1973). 4. Antoine, A. C., "Evaluation of the Application of Some Gas

Chromatographic Methods for the Determination of Properties of Synthetic Fuels," NASA Technical Memorandum 79035, November 1978.

5. Solash, J., Hazlett, R. N., Hall, J. M. and Nowack, C. J., F X , - 57, 521 (1978).

6. American Society for Testing and Materials, Compilation of ASTM Standard Definitions, 4th Ed, 1979.

7. American Society for Testing and Materials, "Freezing Point of Aviation Fuels," ASTM D 2386-67.

8. Humble Oil and Refining Co., Isopar-M, Data Sheet DG-lP, 1968.

9. Cines, M. R., "Solid-Liquid Equilibria of Hydrocarbons," Chap. 8, Physical Chemistry of the Hydrocarbons, A. Farkas, Ed., Academic Press, New York, 1950, pp. 315-362.

183

10.

11.

12.

13.

14.

Williams, A. G., "An Introduction to Non-Electrolyte Solutions," Wiley, New York 1967.

Skau, E. L. and Wakeham, € I . , "Determination of Melting and Freez- ing Temperatures," Chap. 111, Physical I4ethods of Organic Chemis- try, Techniques of Organic Chemistry, A. Weissberger, Ed., Vol. I, Part I., Interscience, New York, 1949, pp. 49-105.

Vold, R. D. and Vold, M. J., "Determination of Solubility," Chap. VII, Physical Methods of Organic Chemistry, Techniques of Organic Chemistry, A. Weissberger, Ed., Vol. I, Part I, Inter- science, New York 1949, pp. 297-308.

Rossini, F., Pitzer, K. S., Arnett, R. L., Braun, R. M. and Pimentel, G. C., "Selected Values of Physical and Thermodynamic Properties of Hydrocarbons and Related Compounds," Amer. Petrol. Instit. Research Project 44, Carnegie Press, Carnegie Inst. of Technol., Pittsburgh, 1953.

American Chemical Society, "Physical Properties of Chemical Com- pounds," Volumes I and 11, Advances in Chemistry Series t15 and 22, Amer. Chem. SOC., Washington, D. C. 1955, 1959.

Table I - Freezing Point Data - n-Alkanes in Isopar-M

Heat of Fusion Entropy of Fusion Freezing Point* AHm(Kcal/Mole) ASm(Cal/Mol-deg.) T ( O K ) m,o

n-Alkane EXP * Lit. Exp. Lit. Exp. Lit.

c-12 8.8 8.80 33.1 33.4 266 264 C-13 8.9 6.81 33.4 25.4 267 268 C-14 10.5 10.17 37.3 38.6 280 279 C-15 11.4 8.27 40.5 29.2 281 283 C-16 12.7 12.75 43.7 43.8 291 291 C-17 13.2 9.68 44.6 32.8 296 295

* - Extrapolated to 100% 1

184

T a b l e I1 - Composi t ion of Mixed S o l v e n t ( % w/w)

S o l u t i o n

A

B

C

D

E

F G

Isopar-M

40 40 80

80 80 50 -

D e c a l i n

40 40

-____

-

B u t y l 'Benzene (normal ) ( s econdary ) ( t e r t i a r y )

- 20 - - - - - - - - 20 - 6 .7 6 .7 6.7 - - 2 5

33 .3 33 .3 33.3

T a b l e I11 - F r e e z i n g P o i n t Data - S o l v e n t E f f e c t

Heat of Ent ropy of F r e e z i n g F u s i o n , A H F u s i o n , AS P o i n t * (Kcal/MoleT (Cal/Mole-Beg) T ( O K ) S o l u t e S o l v e n t m , o

"_-C14H30 "_-C7H16 9.3 32.8 283

Isopar-M 1 0 . 5 37.3 280 sec -Bu ty l Benzene 11 .3 39.0 291 ( L i t e r . ) 10 .77 38.6 279

"-'1 6H3 4

Naphtha lene

"_-'7 H1 6 Deca l in

Isopar-M sec -Bu ty l Benzene

( L i t e r . )

S o l u t i o n A

" B

" c " D " E

" F

" G

sec-Buty l Benzene Isopar-M

( L i t e r . )

1 1 . 2

11 .9 1 2 . 7

14 .3

12 .75

1 2 . 0 12 .4 12 .4 12 .6 12 .7 1 2 . 7

1 3 . 3

3.9 4.7

4.32

37.9 41.3

43 .7

47.8 43.8

41.2 42.6 42.4

42.8 4 3 . 1 43.4 44.7

10 .4 1 1 . 4

1 2 . 2 1

295 289

291

300 291

291 290 292

294 294 293 298

374 4 1 3

354

* - E x t r a p o l a t e d t o 100%

185

v c,, L I ' I . l . 1 I I I I I I I ' I , I I L ' , 1 1 1 1

0.1 0.2 0.4 0.6 0.8 1 2 4 6 8 10 20 40 60 8 5.0

"-ALKANE CONCENTRATION IX. MOLE %.)

W

Figure 1 - Freezing Point vs Concentration - n-Alkanes in Isopar-M

3.8 I S W A R M

r 4.2

z ,.C-BUlYL BENZENE

0 ISOPAR-M

P 4'o

2 4.4 e E 4.6 0 n-HEPTANE

A OECALIN

4.8 1

3.8 1 4.0

2 4.4

Y

0 1 0 2 0 4 0 6 0 8 1 2 4 6 8 1 0 20 40 6 0 8 0 l M

n-TRIDECANECONCEMRATION IX. M M E X I

Figure 3 - Freezing Point vs n-Tridecane Concentration - n-Tridecane + n-Hexadecane in Isopar-M

/

0 169

zi 425

186

Low-Rank Coals -- A Eiesource Kot N l y Exploi ted

Irving Vdender, Chemical and Petroleum Engineering Department, Univers i ty

of Pi t tsburgh, Pi t tsburgn, Pa. 15261

T o t a l recoverable reserves of low-rank coals (subbituminous and l i k g i t e ) are est imated i n t h e hundreds of b i l l i o n s of tons. a l l o f t h i s resource i s l o c a t e d west of t h e idiss iss ippi . increas ing amounts of these coa ls a r e being used f o r u t i l i t y purposes, less than 5% i s cleaned p r i o r t o burning; probably l a r g e r amounts should be cleaned. The f a c t t h a t these coa ls a r e not caking coa ls makes then s u i t a b l e f o r use i n c e r t a i n g a s i f i e r s and t h e f i rs t p l a n t s f o r the convers ion of c o a l t o s y n t h e t i c f u e l s w i l l l i k e l y a r i s e i n t h e west. His- t o r i c a l l y c o a l sc ience has l a r g e l y t e e n confined t o t h e s tudy of bituminous coa ls and t h e r e a r e s e v e r a l so-cal led models of 82-83$ carbon coals . s t r u c t u r e s of low-rank coals, noaever, renairii l a r g e l y a mystery. The c o n s t i t u t i o n of low-rank coals , inc ludine oxygen func t iona l i ty , and t h e e f f e c t s of their ;nineral and moisture contents on r e a c t i v i t y and end use w i l l be discussed.

Almost Although

The

187

PREMIUM TRANSPORTATION FUELS FROM SYNGAS. Energy, A-118, Germantown, Washington, D . C .

There i s an essent ia l need fo r synthetic l iquid transportation fue ls . Indirect liquefaction involving coal derived syngas has gained new in te res t because of new discoveries i n the ca t a ly t i c synthesis of l iquids from C O + H 2 . Catalytic improvements have been made i n the manufacture of CH OH and higher alcohols. Also, higher engine efficiency i s made possible by a combination of high compression r a t i o and ca t a ly t i c decomposition of alcohol t o provide a gaseous fuel t o the engine using heat otherwise wasted.

Conversion of CH OH over ZSM-5 zeol i te ca ta lys t t o h i g h octane gasoline i s remarkable. Also, Zeginning with CO+H2 mixtures, of special i n t e re s t i s the application of ca t a ly t s having d u a l functions (metal + acid) i n combination with shape se lec t ive zeol i tes f o r control of both chemical composition and produet molecular s i ze . hydrocarbon synthesis function makes possible the water gas s h i f t in -s i tu in the reactor, thus permitting the use of syngas of low H /CO r a t i o s , a l t h o u g h with problems in simultaneous optimization of aromatization a n d s h i f t reactions.

G . Alex Mills, Department of 20545

Further, the addition of a s h i f t function to the

188

The Mechanism of Carbon Oxidation

Ralph T. Yang and Chor Wong Department of Chemical Engineering

S t a t e Univers i ty of New York a t Buffalo Amherst, New York 14260

OxidatLon of s i n g l e c r y s t a l g raphi te is being s tudied with t h e technique of

e tch-drcorat ion acd t ransmission e l e c t r o n microscopy, which was developed

by Hen@ et a l . a d Thorns e t al . On t h e b a s a l o r (0001) plane, t h e carbon

atoms surrounding tha aacancy are the a c t i v e sites, which a r e t o b e g a s i f i e d

and a c i r c u l a r p i t i s developed.

(a) t h e rate of C reno-72.1 p e r a c t i v e s i te depends d i r e c t l y on t h e populat ion

dens i ty of t h e a c t i v e sites; and (b) f o r low ac t ive-s i te d e n s i t i e s , C removal

cont inues f o r a prolonged period of t i m e a f t e r 0

phase.

Two sets of r e s u l t s have been obtained:

is c u t o f f from t h e gas 2

Hundreds of c r y s t a l s have been s tudied , which contained vacancies from 0 . 1

t o 60 per pm . dens i ty and l e v e l s of f a t a high dens i ty .

O2 ( i n Ar), t h e rate i s 0.9 C / C / s f o r a vacancy d e n s i t y of l / p m ; 0.6 C / C / s

f o r 10/ym ;

2 The turnover frequency decreases wi th increas ing vacancy

For example, a t 650'C and 0.2 atm 2

2 and l e v e l s of f at about 0.5 C/C/s.

In the argon purge experiments, rates are measured dur ing t h e purge a f t e r

10 min. of r e a c t i o n with 02.

purge f o r s u r f a c e s wi th small vacancy d e n s i t i e s , whereas no g a s i f i c a t i o n

occurs during argon purge wi th h igh vacancy d e n s i t i e s .

The p i t s i z e is more than doubled dur ing argon

G a s i f i c a t i o n of C on t h e edge sites with 0

(a) direct c o l l i s i o n by O2 from gas phase (which fol lows t h e Langmuir-Hinshelwoc

mechanism), and (b) r e a c t i o n with oxides which are chemisorbed on t h e b a s a l

si tes and subsequently migrate t o t h e a c t i v e sites.

i n d i c a t e t h a t t h e anount of chemisorbed oxide i s 0.4

t h e s u r f a c e s wi th low vacancy d e n s i t i e s , and t h a t t h e s u r f a c e d i f f u s i o n

c o e f f i c i e n t is on t h e order of lo-" cm I s , both a t 650°C.

involves two independent processes: 2

Prel iminary c a l c u l a t i o n s

0 per b a s a l carbon f o r

2

189

Cata lys i s i n Coal Liquefact ion

S o l W. Weller

a t Buffalo S t a t e Universi ty of New York

E f f i c i e n t c a t a l y s t s , u s e f u l a t a l e v e l less than 1%, can p lay an

important r o l e i n t h e primary l i q u e f a c t i o n of coa l .

knovledgi of e f f i c i e n t c a t a l y s t s d e r i v e s from empir ica l c a t a l y s t s c r e e n i n g

performed decades ago.

of c o a l i s z t ~ s i c i n g 2: ZII exponent ia l rate.

formulat ion of reactio?. mechanisms t h a t are more soundly based than t h e a d hoc

mechanisms sllggested i n :he p a s t . S t i l l t o be tackled i s t h e ques t ior . of

determining the p r e c i s e r o l e of mul t i func t iona l , e f f i c i e n t c a t a l y s t s i n the

many r e a c t i o n steps t h a t occur during c o a l l i q u e f a c t i o n .

a n e c l e c t i c c o n s i d e r a t i o n of c a t a l y s t systems involving t i n , molybdenum, o r

i r o n which are known t o be e f f e c t i v e i n coa l l i q u e f a c t i o n i n smal l concentra-

t ion . Some of t h e t o p i c s t o be discussed a r e t h e importance of c a t a l y s t

d i s t r i b u t i o n , t h e f a t e of c a t a l y s t components during l i q u e f a c t i o n , and the

c h e s i c a l r o l e played by t h e c a t a l y s t i n a c c e l e r a t i n g the r e a c t i o n s occurr ing

i n l i q u e f a c t i o n . The last problem i s t h e least understood and p r e s e n t s the

g r e a t e s t chal lenge f o r f u t u r e research.

Most of our p r e s e n t

Ziy c o n t r a s t , our understanding of t h e organic chemistry

T h i s understanding w i l l permit

This paper p r e s e n t s

190

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