University of Nigeria Research Publications

UWANTA, Ema-Ime Jimmy

Aut

hor

PG/M. Sc/89/7617

Title

The Distribution of Aromatic Sub -Types in

the Higher Boiling Fraction of Some Nigerian Well-Head Crudes

Facu

lty

Physical Sciences

Dep

artm

ent

Pure and Industrial Chemistry

Dat

e

May, 1992

Sign

atur

e

ACKNOWLEDGEMENT . .

The successful completion of t h i s s tudy h a s been

made poee ib l e by the assistonce of my pro j e o t superv iaor , . I I -

Dr. C.A. Nwadinigwe. I thank him f o r g u i d i n g me through- I

o u t t h e p r o j e c t and f o r reading through t h e work, 'making 1 a number of suggest ions .

I also ackaowledge with thanks the Head af Depart-

ment, D r . S,O. Onyiriuka, Dr. M e Kellek-" --I'

members o f s t a f f i n the Department f o r L I-.

Nsukka a succes s fu l one,

I w i l l eve r remain g r a t e f u l t o my pa ren te , Chief and

Mre. U.A. Umoren f o r t h e i r f i n a n c i a l support throughout

Above all, I am g r a t e f u l t o my husband f o r h i s

patience, moral wppoft and encouragement du r ing t h e

course of th fa work.

To Almighty Cod be a l l t h e g lory , Amen. I

I

E.I.J. Uwanta ( ~ r s ) Dept. o f Pure and Jnduetrial Chen,: U, N, N. I

DEDI CAT1 ON

To my husband, Ims and

my children Ekeminl, N tiense and I b e ~ UUUU.

Chapter

ACKNOYLEDGENENT. . . . . . . iii

DEDICATION. i v

TkBLE OF CONTENTS.

ABSTRACT.

I . 0 Introduc tign and Histarical Background.

1.1 Origin of Petroleum. . . . . .. 3 b

I . 2 Oocurrence of Petroleum in t h e World. 6

I ConstituentsofPetroleum. . . . . 10

1.3.1 Paraffinic and Olefinic Componenta of Crude O i l . m . . . . . . . . . .. I1

Normal Paraffins. . . . . . . I soparaf f ins. , . . . . . . Olef ins (Alkenes) . . . . . . . Naphthenic Components of Crudes. . . Gromati c Hydrocarbons, . . . . Non-hydrocarbone i n Crude Oil. . .

e O i l . . . ..,,,,,,,, ,,,,,,,,,, -,- ,--de O i l 8 . . . Sulphur Compoun,ds i n Crud1

Nl t r n ~ n n Cnmnnundn in Crur

v i . Page

Oxygen Compounds i n Crude Oila. 25

High Molecular Weight N , S, 0, Bompounds. 26

Drganamatalli c Compounds. . . .* n Physical Methods 'o f Analysing Crude O i l . n V i eco si ty. . . . . . . . n Flash Point. . . . . . . . 28

Cloud Point. . . . . . . . . 28

b i l i n d Point. . . . . . . . . 28 1 .

I. 4.5 Spec i f i c Gravity. . . . . . . 28 I

1.4.6 Wax and Pour Point. . . . . . . 29 B *

1.5 Petroleum Refining. . . . . . . 30

I. 5.1 Atmospheric D i s t i l l a t i o n of Crude o i l . 31 \ - 1.5.2 Isomerisat ion Process. . . .

-- 32

I. 5.3 Ca ta ly t i c Alkylation. . . . . 33

Ca ta ly t i c ~eforming. . . . . 34

Ca ta ly t i c Cracking. . . - . 35

Methods of Analysing Petroleum. . . 36

Analytical Methods f o r the Fractions. 39

1 nf ra-red Spect rosmpy. . . 40

kppl ica t ion of Infra-red Spectroscopy. 42

Gae Chromatography. . . . . 43

Nuclear Mame tic Resonance Spectroscopy. ,4 5

Application of Nuclear Magnetic Resonsnce. 48

v i i .

Chapter Page

U l t r a -v io l e t V i s i b l e Spectroscopy.. 49

h p p l i c a t i o n of U l t r a - v i o l e t Spectroscopy. 52

Separa t ion Techniques, . . .. 54

S i l i c a - g e l Column Chromatography. 54

Thin Layer Chroamtography. . . . . 55

Pape r Chromatography. . . . . 60

Ana lys i s on Niger ian Crude Oile. 63

A i m of t h i e P ro j ec t . . . . . 67

Reeul t~ and Discuseion. 10 68 ' DiatiElation of t h e Crude. . . 71

Separakion on a q u a n t i t a t i v e bas is . 7 3

S p e c t r o s w p i c Ana lys i s of t h e Aromatic Sub- types. . . 75

D i e t i l l a t i o n of t h e Crudes. . . 81

Deasphalt ing of Residue ( > 3 0 0 ~ ~ ) . 8 2

Determf nat ion of Benzene Insolubhe F r a c t i o n 8 2

Sepfrratibn of the Bottoms ( 2300%). 84

Sepa ra t i on of Aromatice i n t o Ring Classes. 85

Thin Layer Chromatography (T.L. C. ) of t h e

Aromatics obtained. . . . 86

REFERENCES. 88 WPPEN DI X . . o m 93'

v i i i .

LIST OF TABLES

Table Page

I Petroleum Const i tuents . . . . . . . 6

' X I ~s t f i rna ted World Natural g a s Reserves.. 7

111 O i l Production and Consump-tion l e v e l s i n t h e European Coamuni ty. . . . 8

I V Estimated World O i l Resource. . * 9

V Hydrocarbon Identif led i n t h e Urea adguct , , from Nigerian Crude O i l , bp 340 - 480 C. I 2 .

V I D i s t r i b u t i o n of Aromatic Subtypes i n ~ e t r o l e u i Produc ts I8 '

VII Nitrogen Content According t o Distillation , . F r a c t i o n s of Wilmington, C a l i f o r n i a Crude O i l . 24

VIII Produc ts of Crude O i l D i s t i l l a t i o n Unit i n Petroleum Fract ion.

I X Absorption of ~ r o m a t i c Compounds i n I r region. 42 . I

' x Absorption o f Aromatics i n t h e UV-region. 53

H Paper Chromatographic Reeult of Po lycyc l ic Tar Hydrocarbon. . . . . . . . 62

X I 1 OAPI of Crudes .under Inves t iga t ion . . a

72

X I 1 1 D i s t i l l a t e from Ughelli-Eaat Crude, . 9$

X I V D i s t i l l a t e from Utorogu Crude. . . 93

xv L Distil late from Yorla 9 Crude. . . 94

XVI Quantitative R e s u l t s Obtained from analysis. g4

X V I I Q u a n t i t a t i v e Reeu l t s Obtained f a r t h e t h e Aromatic S u b t y p e s , . - . . 9.4

Page

Distribution of firomatic Subtypes i n S o m e Nigerian Crude 0118. . . 95

Infra-red Spectrum o f Di-aromahic f om 6 Ughelli-East bo tton Fraction () 300 C) . 95 ;

Infra-red Spectrum of Disromatica from . I

U torogu bot t o r f ract ion- ( 7 JOO'C) 96

Infra-red Spectnu of Diaromatlcs from Yorla 9 bottom f raot ion ( 3 300%). 97

Infra-red Spectrum of Trisromatics from Ughelli-Eaet bottom fraation (> 300'~). 97

Inf ra-red Spectruga of tri-aroma'tics from + Utorogu b a t t o r f r a c t i o n ( 7300'~). 98 N.H.R. Spectrum of Diaromatics from U ~ h e l l l - B a s t bot ton f r a c t i o n ( ?300%). 98

N.W,R. Spectrum of di-aromatics from Utorogu bottom f r a c t i o n ( > ~ O O ~ C ) . 99

N.H. R. Spectrum of tr i-aromatiae from Ughel l i -Eas t bottom f r a c t i o n ( > 300~~). .. 99

N.M. R. Spectrum of Triaromatice from Utorogu bottom f r a c t i o n ( > 3 0 0 ° ~ ) . ' 99

N.M, R. Spectrum of Di-aronatigs from Yorla bottopr f r a a t i o n (2300 c). 100

N.H, R, Spectrum of t r fa romat ice from Yorla gL bottom f r a c t i o n ( ) 300%). 100

LIST OF PICURES .* - . ,

Figure Page

I Examples of aromatica ark8 Cycloalkano- aromatics (naphthenes aromatics) found i n Crude oil, a. . I9

I1 Examples of Sulphur in crude o i l s , . . 23

I11 Separation pattern for pehroleum fraction, 38

I V The prooess of thin layer chromatography, 58

V Separation pattern for t h i s project, , . 83

VI Correlation between the relat ive chemiaal ehif ks of the pro ton resonance i n naphthalene and anthracene. . = . a . 104,

VII The spectrua of phenanthrene. . . I@

ABSTWCT

Up t o 1975, muah o f t h e r e sea rch on hydrocarbone i n

n a t u r e has concentra ted on s a t u r a t e d and olefinic hydro-

carbons pr incipal ly becauae of the r e l a t i v e e a s e o f ma-

ly sia, By comparison,- t h e study of aromat ic hydrocarbons I has been neg lec ted , but i n t e n s i f i e d research e f f o r t s

a rose from t h e environmental and p u b l i c h e a l t h questions

poeed by the t o x i c i t y of many aromatics,

&romat ics present i n c rab o i l s produce red o i l e and b I .

heav ie r fractions. The red o i l s are der ived mainly from ,

areniurn i o n s of po lycyc l i c a romat ics formed by t h e . t

pro tona t ion of t h e aromat ic res idue by the acid c a t s l y e t s

used i n r e f i n i n g , The magnitude of t he problem beam a

d i r e c t r e l a t i o n s h i p t o t h e concent ra t ion of aromatics I

p r e sen t i n t h e crude and t h e str?.e&t;h~of t h e a c i d i c

c a t d y s f used,

I n t h i s work, the .aromat ic conten t of the high

b o i l i n g f r a c t i o n of t h r e e well-head crude o i l samples

, from d i f f e r e n t l o c a t i o n s i n Nigeria,r Oan'ely,,Xofla,- U#hel l i ,

East and Utorogu, with O ~ ~ j a f J9.30°, ~3.8' and 23.70 b

r eepec t ive ly were investigated. Each cruds was d i s t i l l e d

under atmospheric pressure, The percent of fraction

( )300'~) were 21.1; 44.4 and 57.6 for Yorla, Ughelli-

East and Utorogu reapectiwly. The components of the

bottom .f rsction ( ~oo'c), saturated. hydrocarbon, arona-

t i c ' hydrocarbone and resins were separated using adsorp-

t i on chromatography with silica-gel. The aromatic f r a c t i o n

obtained using benzene as t h e e luent was f u r t h e r chrona-

tographed on alumina column with emphasis on the d i - and . t ri- aromati cs. b

The r e s u l t obtDioed show a percent range of 6.26 +

9.5; 12.8 - 21.7 m d 21.1 + 27.6 f o r Yorla gLr

Ughelli-East and Utorogu reppect ively the sum of di - and

tri-aromatics. i n the crudes.

Thie work has demonstrated the occurrenee o,f di- ,

tri- and polparomatics hydrocarbons i n Nigerian crudes

aa inferred from both n.m.r, and i . r spect ra , I t a l a o

shows tha t the percentage of aromatics v a r i e s from crude

o i l to crude o i l wi th the Utorogu crude g iv ing t h e highest

concentrat ion o f aromatics ( 21.1 4 27.6 wt.$).

T h i s i s a convenient d e f i n i t i o n , s i n c e i t d e l i n e a t e s

a l s o a d i s t i n c t f r a c t i o n i n most s e p a r a t i o n s , e s p e c i a l l y

by chromatography. Heqero-aromatic compounds wi th

(N, S, 0) of t e n a r e inc luded with t h e a roma t i c s which

they accompany i n s e p a r a t i o n s ; however t h e r e a r e d i s t i n c t

d i f f e r e n c e s i n r e a c t i v i t y . The a romat ic hydrocarbons

d i f f e r from t h e i r s a t u r a t e d and o l e f i n i c ana logs i n solu-

b i l i t y , v o l a t i l i t y , l i g h t ab so rp t i on , a s s o c i a t i o n , r e a c t i - 6

v i t y , b iodegrada t ion and p h y s i o l o g i c a l a c t i v i t y , Thus,

they a r e a s e p a r a t e group of compounds i n terms of geo-

chemisbry and of environmental s i g n i f i c a n u e and f a t e .

The composit ion o f many n a t u r a l PAH assemblage i s

unknown and t h e i r sou rce s a r e t r u l y mys te r ious - examples

2 are benzopyrene i n a s b e s t o s , f l u a r a n t h e n e and p i cene i n

mercury o r e s 3 andPerJ lene i n r e c e n t c l a y s and ca rbona t e

4 muds . I n t h e s e p a r t i c u l a r samples, t h e PAH assemblage

appea r s t o be e h p l e ; y e t i n many a n c i e n t sediments and

i n f o s s i l f u e l s we encounter thousands, if n o t hundreds

o f thousands o f homologous and isomeriu aromatics .

LITERtZ'KJRE REVIEW

a I , ORIGIN O F P m R O L m

5 Mast theories concerning the arigfn of petroleum

p o s t u l a t e wi th animal and vegetable origin, I t is e l a o

suggested that petroleum originated from biological .

.matter; o r ~ a n i c matter converted under suitable condi t ions ,

There i s a l s o genera l agreemat ,that petrolem was

formed from organic ma t t e r nea r shore and In marine

deposit deficient i n oxygen and assoc ia ted with minera l s

converted by t i m e and p r e s s u r e Into l imestone, dolomite,

sandstone and similar rocks, The Concentration of

organic mat ter i n t h e o r i g i n a l d e p o s i t s may n o t have been

high but petroleum gas and l i q u i d s have migrated and

gathered in places favouring r e t e n t i o n e.g, seal-of f

porous sand-stones. C&er long p e r i o d s of time, carbo-

hydra tes and p & t e i n s a r e probably destroyed by b a c t e r i a l

a c t i o n leaving the f a t t y o i l s which a r e more r e f r a c t o r y

t o bacterial o r chemical des t ruc t ion .

Consequently, there are two modes of formation of

petroleum, t h e ' i n s i t u ' , where p l a n t d i e s and t h e

* remalne a r e bur ied and compres8ed, t h e r e may be on ly . _ .

very l i t t l e migra t ion o r t he m o u n t of vertiaal migra t ion

i s negligible, There is also the dr f f t mode of f o r n a t i o n

o r migra t ion of o i l , where p l a n t d e b r i s mixed with sand,

gravel and e a r t h a r e eroded from the land by i c e , water

and sand to form sediments. Anaerobic b a c t e r i a i n t he

bug f eed on the dead ma t t e r and change the f a t t y acide

o f which i t i s composed t o petroleum-like compounds other-

wise known as kerogen. The sedtmenta themselvee hc6r - I

p o t a t i d & the kerogen are con t inua l ly . being added to the

bottom l a y e r e and uompres~ed by weight of l a y e r s above

to form eedimentary rocks, such a e l imestone, eandstone

clay and &alee, Fur ther oampactfon of t h e keragen

resulta i n the r e l e a s e of more gas and the formation of 6 -

petroleum.

Kerogen now f o m e d mig ra t e s through porous rock

Payera and rrettlee on ildpervioue rocks. The g a s now

a e t t l e e on top of the crude o i l , t h a t i s why the gas

comes out f i r a t during d r i l l i n g .

I n Niger ia , due t o l ack a$ appropr i a t e technolgy

to harneee the gae, several m ~ t h o d e are introduced 8.g.

r e - in j ec t ion and f l a r i n g . Recent l i q u i d petroleum g a s

(LPG) at Port-Harcourt i s an e f f o r t t o ha rnes s f l u e g a s

i n t o domeetic and commercial f u e l sources.

During d r i l l i n g , t he crude o i l i s separa ted from

t h e o i l and Clay {gan@e). A f t e r pre-treatment i t l a

hea ted and paseed i n t o t h e f r a c t i o n a t i n g column, where

t h e f r a c t i o n s a r e separa ted according t o t h e i r d i f f e r e n c e

i n b o i l i n g po in t as shown i n Table I below. Any two

fraotione falling in fhe meme boiling range are further b

classified i n terma of d e n s i t y as l i g h t o r heavy d i s t i -

l l a t e .

Petroleum bo t tome a r e f u r t h e r cracked by various

methods t b o b t a i n g r e a t e r y i e l d s of improved g a s o l i n e s

at the expenee of t he gas and heavy f u e l o i l f r a c t i o n s .

The f r a c t i o n make-up of a crude h a s a d i r e c t bear ing on

how i t w i l l be subsequently processed. The p r o p e r t i e s

o f s p e c i a l importance to ' t h e p rocess ing and use of

petroleum and i t a product8 a r e t h e i r pour p o i n t , f l a s h

p o i n t , f i r e p o i n t , s e l f i g n i t i o n p o i n t and explosiveness.

7 Table I t Petroleum Constituents . ! _

F r a c t i o n D i tilla at ion Carbon number range

Gas below 20 - C4 20 - 60 Petroleum e t h e r '5 - '6 '

Lig ro in (1 igh t naphtha) 60 - I00 C6 - C7 Natura l ' g a s o l i n e 40 - 205 C5 - CIOand oyclo-

Kerosene . - a lkane .

I75 - 325 C12- CIBmd aromatics

g a s o i l above 2'75 CI *and. h ighe r B

1.2 Occurrence of Petroleum (c rude O i l ) i n t h e World

On thermal baa i s , g a s r e s e r v e s a r e es t imated t o be

equ iva l en t to tamewhere one h a l f and one t h i r d o f world ~.

reserves of conventional o i l resources , However, as i s

the ca se with o t h e r f o s s i l f u e l s , t he d i s t r i b u t i o n of

r e sou rces i s uneven as shown i n Table I1 below. Tables

I11 and I V show the l e v e l of o i l product ion and consump-

t i o n i n the European community and t h e es t imated world

o i l resources respectiuely,

8 Table 11: Estimated World natural gaa reserves ' ' {world natural gas reserves January; I980

Region. - . NTOE Percentage of Total 1

North America 32,000 a I5

South b e r i c a 15,000 7

Western Europe 11,000 5 . .

Eastern Europe 65,000 31

Middle East 50,000 24 4

Far East 11,000 5

MT06 - Million tonnee of O i l Equivalent. I

\

Table 11x8 Oil Production and Consumption l e v e l e i n 9 the European Communi t y

Country Production ~ o n s u a p t i o f l Net Import +

Iq81 1981 I980 I981

Germany 4.700

France 4.200

I t a l y 1,720

Ne therlande I , 580

Belgium

Luxembourg

United Kingdom 85. I00 <

Ireland

Denmark

Greece

t T b -cori*tive expenditure of energy in the Community.

i Excluding trade within the community.

Table IV*': Estimated World O i l ~esourcea* ' -

, .

Region O i l ( m i l l i o n s of tonnea) I

I

North America 28,000

Soviet 'union and Eaatern Europe

Western Europe, Japan, Australia, New Zealand, $outh Uf r i c a and I erael

Latin America. ~ o ; t h Africa and South East Asia

Middle East and North '

Africa .

China and Centrally Planned Asian Economies

Total

r Hafele, A. -- et al. Ebergy i n a f i n i t e world paths to

a sustainable future. Vol. I .

1.3 Constituents of ~ u t r o l e u m

Crude petroleum i s made up o f thousand8 of different

themica1 eubatanoee i nc lud ing gases , l i q u i d 8 and mlide- ranging

and -from methane t o a spha l t . . The prina ipa l camp-

ounds a r e the s a t u r a t e d hydrocarbons ( p a r a f f i n a ) and

cyc loa lkanes (naphthenes) , aromat ic hydrocarbons, inclu-

d i n g pure aromat ics , . cycloalkano-aromatic~t (naphtheno-

Cyoloalkanoaromatics are most frequently benzo- b

thiophene de r iva t ivee . The o t h e r compounds o f petroleum

a r e r e s t n s and aspha l tenes , made o f t h e h igh molecular

weight po lycyc l i c ' f r a c t i o n o f crude comprising N p 3, and

- 0 atoma. Aaphaltenes are i n ~ d . u b h hn l i g h t a3kanes and

t h u s prec ip i ta ted . ; with n - hexane. Resins a r e more

eo lub le , bu t are l i k e w i s e very p o l a r and are r e t a i n e d on

alumina when performing l i q u i d chroaatography.

, I n terns of sulphur content ; ,pet iy l -em i s classified1'.

i n t o law-sulphur (0.1 - 0.5% S) medium sulphur (2.5 - ., .

3s 8) and high mlph4r (up t o 5% 9). Nigerian brude o i l '

goes not contairn much nitrogen and lacka sulphur. This

is why i t is termed Wsweetm, I t is mast suf t a b l e f o r

t r a n s p o r t f u e l s because i t c o n t a i n s more of t h e s a t u r a t e d

hydrocarbons.

The inorganic i m p u r i t i e s i n crude i nc lude water

which may be present in a form easily separa ted from t h e

petro'leum by settling and as p a r t of stable emulsions,

The a;& content of crude o i l i s hundredth o r even a

few thousandth of one percent, There a r e a l s o mechanical

impurities In form of sand a ~ d c l a y p a r t i c l e s ,

'I 3 1 Paraffinic and O l e f i n i c Components of Crude Oil ( Saturated Hydrocar&-n s)

The proport ion of paraffin i n crude o i l s vary s t rong ly

with t h e type of crude. From a given crude t h e pro par ti^

of p a r a f f i n i c hydrocarbon u s u a l l y decreases with

i n c r e a a i n ~ molecular weight, I n t h e gaso l ine ranEe f o r

ins t ance , paraffin con ten t up t o 8096 a r e abstrved, whereas

i n t h e l u b r i c a t i n g o i l range, a 30% p a r a f f i n content I s

except ional ly high. Some crudes y i e l d l u b r i c a t i n g o i l

f r a c t i o n s which contain no p a r a f f i n a t al l .

'I, 3.2 Normal Paraffin

Hydrocarbons of t h e normal p a r a f f i n type occur i n

most c rude o i l s but i n varying propor t ions , Anderson, P. .C,

and Whitehead E. v.'12 use urea adduction method on t h e

saturated por t i tm of a Nigerim middle d i s t i l l a t e kp

340 - 480% coupled with gas- l iquid chrmatography and

peak enhancement technfque on two d i f f e r e n t s t a t i o n a r y

The inorganic impurities i n c rude inc lude water

which may be present In a form easily separa ted from t h e

petroleum by s e t t l i n g and as p a r t of s t a b l e emulsions.

The ash content of cmde o i l i s hundredth o r even a

f e w thOusatlUth of one percent, There a r e also mechanical

impurities i n form of sand aqd c l a y p a r t i c l e s ,

1.3.1 Paraffinic and OLefinic Components of Crude O i l '( Saturated ~ y d r o c a r 6 n s )

The proport ion of paraffln in crude o i l s vary s t rong ly

wi th t h e type of crude. From a given crude the proportlor

of p a r a f f i n i c hydrocarbon u s u a l l y decreases wi th

i n c r e a s i n g molecular weight, I n t h e gasoline range f o r

ins t ance , paraffin con ten t up t o 8% a r e ebsemred, whereas

i n t h e lubricating o i l range, a 3@/, p a r a f f i n con ten t i s

e x c e p t i ~ a l l y high, Sme crudes y i e l d lubr ica t ing: o i l

f r a c t i o n s w h i c h conta in no p a r a f f i n a t a l l ,

1.3.2 Normal Paraffin

Hydracarbons of t h e normal p a r a f f i n type occur i n

most crude ails but i n varying proport ions. Anderson, P. C,

and Whitehead E. u s e urea adduction method on t h e

saturated por t ion of a Nigerian middle d i s t i l l a t e bp

340 - 4 8 0 ~ ~ coupled with gas-liquid chrmnto~rap hy and

peak enhancement technique on two d i f f e r e n t s t a t i o n a r y

pbses t o 'idmtify the principal component present i n

the crude o i l , The hydrocarbons with carbon numbers i n

the range CZ0 - '32 are l i s t e d i n Table V below.

Table 'V: Hydrocarbons Identified in t h e Urea Adduct

from Ninerim Crude Oil b.p 340 - 480%

Principal Components

n - alkanes

2 - methyl alkanes (iso-alkanes)

3 - methyl alkanes (anteisoalkanes) I

I

I - cyclapentyl alkanes

I - cycld alkanes (unidentified)

Minor Cmponents

4 - methyl alkanes .

5 - methyl alkanes .

I. - cyclo-hephyl alkanes

The unidentified component may perhaps be the

homologous s er i e s of 2,6-dimethyl alkanes that had been

reported I n Nigerian crude o i l by Schenche and his

co-workers, I 3 Many of ths hydrocarbon series l i ~ t e d

above have been i d e n t i f i e d a l a o i n Agha ~ar iI ' I crude

o i l as well as in sediments, I5

Straight chain s a t u r a f ed hydrocarbons a r e found

throughout the b o i l i n g rage of petroleum, From Ponea

crude, a l l normal p a r a f f i n s up t o n - dodecane .have

been i s o l a t e d under American Petroleum I n s t i t u t e

Research p r o j e c t - ~(LPI-6). The 55 - 180'~ f r a c t i o n

con ta in ing about one- t h i r d normal pera f f i n . I6

S t r a i g h t cha in normal p a r a f f i n have much lower

oc tane nunbers than the h igh ly branched p a r a f f i n s . I n

t h e h igher b o i l i n g ranges of kerosenes and d i e s e l f u e l e ,

normal p a r a f f i n s improve the burning q u a l i t i e s , smoke

p o i n t and ce t ane number bu t they have much h igher me l t i ng

p o i n t s ' .and hence t h e i r presence adverse ly a f f e c t s t he

cloud p o i n t , pour po in t of heav ia r o i l s .

N-peraffins can be removed s e l e c t i v e l y by molecular

s i e v e s i n a high .degree of p u r i t y i n which form they a r e

most va luab le f o r manufacture of de te rgen ts , S tocks

r i c h i n normal p a r a f f i n s a r e a l s o p r e f e r r e d f o r the

b a c t e r i o l o g i c a l production o f p r o t e i n e.g. n-alkane,

n-butane

' H H H H

I eoparaf f i n s

Many branched alkanes containing I0 carbon stoma

o r l e s s have been i d e n t i f i e d . I7 Beyond CIO, t h e series

of i s o p r e n o i d s up t o C and o n l y a few o t h e r i s o a l k a n e s 25 '

such as squa lene have been d e f i n i t e l y i d e n t i f i e d . This

s i t u a t i o n r e s u l t s from t h e ve ry l a r g e number of p o s e i b l e

i s o m e r s and t h e mall c o n c e n t r a t i o n of h i g h e r molecu la r b

w.eight i s o a l k a n e s . The h i g h e s t i n d i v i d u a l c o n c e n t r a t i o n

o f i a o a l k a n e e i s found i n t h e C k - C8 range, namely

2-methyl - o r 3-methyl-hexane and/or hep tane and i t may .

r e a c h more thap I$ of t h e c r u d e o i l .

I. 3.4 Olef ins ( ~ l k s n e a )

O l e f i n a are' *regent i n trace q u a n t i t y i n petroleum.

The r e e e a r c h wark c a r r i e d o u t by Fred and P u t s e h e r I8

on Pennsylvanian arudea show l a r g e p o r t i o n o f o l e f i n s .

The I n f r a - r e d speatra o f t h e Pennsylvanian c rude as well . it conta ins

as a l l d i e t i l l a t e ' f r a c t i o n , show t h a t f about 3$ o f trans-

I ' I o l e f i n ( i . e RCH 1 HCR with R and R I n trans p o e i t i o n ) .

By chemical 'methods (nitrollen tetroxida,. a d s o r p t i o n ,

oxidat ion with perbenzaic a c i d and with ozone) it has

been ahom t h a t non-aromatic pa r t of 310 - 340%

fraction arc less c y c l i c than their accompanying . saturates, mare than hal f of the olefinic miole~ules

being nm-cyc l i c ,

7.3.5 Naphthenic Comp~nmts of Crudes

The propor t ion of naphthenic hydrocar.bon varies with

t h e type of crude, Isolation of naphthents from crudes

has been successful i n t h e gasoline rmge, I n t h e Maher b

f r a c t i o n s , the number of isomers increases very r a p i d l y

because of - 1. t h e large v a r i a t i o n i n the arrangement of carbon

atoms per ring;

2, t h e p o s s i b i l i t y 'o f c i s - t r a n s isomerism and r i n g

stereo-isomerism; . and

3. t h e divergency i n t h e way i n which d i f f e r e n t

naphthenc rings may be l i n k e d up.

The two main classes of naphthene compounds p r e s e n t

i n c rude petroleum are cyclohexane

and cyclopentane

I. 3 6 Aromatio Hydrocarbons

A 1 1 crudee contain aromat ic compounds i n p ropor t ion

varying from I0 - 50$ o r even higher. True aroaatfce

are molecules containing only aromatic rings and a small

nunrber of short chaina. Compounds belonging t o t he

va r ious b a s i c t j p e s have bean iden t i f i ed1? - benzene

ring), naphthalene ( 2 r i n g s ) , phenanthrene and

an thraoene ( 3 r i ngs ) , pyrene, benzanthracene and ohrysene

( 4 r ings) . The i r d e c u l a r maea formula i a C,.,HZn-* where b

p v a r i e e with t he number of r i n g s ae shown i n f i g . I

below. Benzene ( p = 6 ) , naphthalene ( p - 12) and

phenanthrene ( p 8) t y p e s a r e t h e most abundant.

In t h e gasoline f r a c t i o n s , a l l known aromat ics a r e

p resen t . The benzene con ten t i s u s u a l l y mal l compared

with ainple benzene homologues such as t o h e n e , t h e

t h r e e xylsnes (0-, m-, and p-xylene) e t c .

- 20 Rowland & a. used a method o f hydrous p y r o l y s i s

(oloeed vessel autoclaving i n t h e prsaenoe o f excess

water) o f organio-rich rocks t o gene ra t e o i l s which . c l o s e l y resemble n a t u r a l crude o i l s i n t h e i r broad

c h a r a c t e r i s t i c s and compoei t ion. Hydrous p y r o l y s i s

c a r r i e d o u t i n 3 days o f a do lomi t i c s i l t s t o n e (permian,

Marl S l a t e ) at S O , 300, 320, 340 and 3 6 0 ~ ~ produced

s i g n i f i c a n t amounts o f o i l s i n which t h e a romat ic hydro-

ca rbons were one and a h a l f t o two t imes as abundant as

t h e s a t u r a t e d hydrocarbons. The o v e r a l l composit ion o f

t h e a romat ic hydrocarbons was similar t o most c rude o i l s :

t h e major component i s o l a t e d by t h i k method from n a t u r a l

o i l s and from p y r o l y s a t e s were C a lky l -naph tha lenes 1-4

and a l k y l a t e d su lphu r c o n t a i n i n g aromat ics .

Other a romat ic compounds which a r e n o t abundant i n

n a t u r a l c r u d e s l i k e an th racene , m e thy1 an th racene and

D i d t s hydrocarbon were a160 produced. The p r o p o r t i o n s

o f each o f t h e s e r e l a t i v e to phenanthrena i n c r e a s e d wi th

i n c r e a s e d p y r o l y s i s temperature. They concluded t h a t

t h e s e compounds a l s o r e s u l t from t h e h igh temperature

used i n p y r o l y s i s experiment compared to the temperature

a s s o c i a t e d wi th n a t u r a l o i l genera t ion .

Gradient e l u t i o n chromatogrnphi c (G. E. C. ) s e p a r a t i o n

me-thod has been found s a t i s f a c t o r y f o r a romat ic concen-

t r a t e a from kerorsene, c racked o r v i r g i n g a s o i l s , FCC

feeds tock and r e s i d u a l s . Only s u b t l e exper imenta l

d i f f e r e n c e s e x i e t between ext remes (kerosene r e s i d u a l s )

s i n c e t h e i r p re t rea tment steps a r e i d e n t i c a l .

Table V I shows aromat ic type d i s t r i b u t i o n f o r a

v a r i e t y o f petroleum syetems. One example from hydro-

genated c o a l i s also c i t e d . 21

Table V I : D i s t r i b u t i o n of Aromatic Sub-types i n

Petroleum Produc t s (weight Percen t of To ta l o i l )

Mono D i - - T r i - Poly- Aromatic aromat ic aroma t i c

4 Niger ian gas o i l 10.7 13.6 2- 3

Venezuela Middle gas o i l 14.6 18.5 1.8

Kuwait vacuum r e s i d u a l 2- 7 37.7 3.7

Kuwait gas o i l 1.2.2 22.0 0.34

Cracked g a s o i l 1.8 30.4 2.5

K e ro sene 20.2 I 2 * 2 2.8

Hydrogenated c o a l , . '

t i i s t i l l a t e 55.1 26. 4 1.5

H Benzene 6 6

C ~ ~ H ~ 2

' e t rahydronaphthene

Trimethyl-naph t h a l e n e

Dimethyl phenanthrene

'18~16 methyl cyclo-pentano-

phenanthrene

k l k y l t e t r a h y d r o - phenanthrene

Tet rahydro t r i m e t h y l p i c e n e

F i g u r e I: Examples of a r o m a t i c s and cycloalkanb-aromat ics

(naphthen a romat ics ) found i n c rude o i l s

I. 3.7 Non-hydrocarbons i n Crude O i l

Crude petroleum u s u a l l y c o n t a i n s Borne s u l p h u r ,

n i t r o g e n and oxygen i n a d d i t i o h t o carbon and hydrogen,

and s o r e of t h e s e a r e a s s o c i a t e d wi th m e t a l s such as

vanadium and n i c k e l i . e they a r e o r g a n o a e t a l l i c i n

n a t u r e . These o r g a n i c non hydrocarbon components a r e

d i s t r i b u t e d through t h e whole b o i l i n g range o f a c rude

o i l , ' b u t appears , mainly i11 t h e h e a v i e r d i s t i l l a t i o n

f r a c t i o n and t h e n o n - v o l a t i l e r e s i d u e , b

The c o n c e n t r a t i o n of t h e s e non-hydrocarbons i n any

f r a c t i o n is r e l a t i v e l y smal l b u t t h e i r i n f l u e n c e i s

much and impor tan t i n t h a t a c i d i c components such as t h i o l s

and c a r b o x y l i c a c i d s promote c o r r o s i o n o f m e t a l e q uipment;

r e fo rming c a t a l y s t @ employed i n t h e p r o d u c t i o n o f motor

g a s o l i n e are s e r i o u s l y a e a c t i v a t e d by s u l p h u r compounds;

t r a c e m e t a l s ( v , N i ) becone d e p o s i t e d on and p a s s i v a t e and

/or po i son c a t a l y e t e employed i n d e s u l p h u r i Eiation o f f u e l

o i l and c a t a l y t i c c r a c k i n g of heavy d i s t i l l a t e s . The

c o l o u r and odour of c rude o i l s stem mainly from Ni t rogen,

Sulphur , Oxygen compounds t h a t a r e c o n c e n t r a t e d i n t h e

l u b r i c a t i n g o i l (Cp6 - '40) and res id ium ( > a s p h a l t i c b i tumen f r a c t i o n .

1.3.8 Su lphur . Compounds i n Crude O i l

Sulphur i s t h e t h i r d most abundant a tomic c o n s t i -

t u e n t of c rude o i l s , f o l l o w i n g carbon and hydrogen,

I t i s p r e s e n t i n medium as w e l l as heavy f r a c t i o n s of

c rude o i l s , I n low and medium molecu la r weight range

(up t o ~ 2 ~ ) s u l p h u r i s a s e o c i a t e d wi th C and H, . In

t h e h e a v i e r f r a c t i o n 8 of c r u d e o i l s , i t i s f r e q u e n t l y

i n c o r p o r a t e d i n l a r g e p o l y c y c l i c .molecules compr i s ing

N, S, 0.

Sulphur compounds i d e n t i f i e d i n t h e l i g h t and

medium f r a c t i o n s of c rude o i l , (up t o CZ5 ) belong t o

f o u r main c l a s s e s of unequal importance - ( a ) t h i o l s a l s o c a l l e d mercap t a n s ,

( b ) s u l p h i d e s ,

( c ) d i s u l p h i d e s ,

(d ) th iophene d e r i v a t i u e s .

T h i s i s shown i n f i g u r e I1 below.

T h i o l s can be thought a6. d e r i v e d from H 2 S by

s u b s t i t u t i o n of an a l k y l o r c y c l o a l k y l r a d i c a l for a

hydrogen atom. Normal and i e o a l k a n e , t h i o l s cycle- > p e n t a n e t h i o l and c y c l o h e x a n e t h i o l have been iden t i f l ed

i n petroleum. 22 Most t h i o l s havf a low molecu la r

weight ( l e s s than 8' carbon atoms). The most abundant

i n Waeson crude o i l , Texas i s e t h a n e t h i o l and amounts

on ly t o 0.0053$ by weight o f t he crude.

Su lph ide s . can be thought of as de r i ved from H2S

s u b e t i t u t i o n of 2H atoms by a lkane group. They a r e

u s u a l l y o f very low abundance,

Disu lph ides have a s i ~ i l a r s t r u c t u r e as s u l p h i d e s

but t h e au lphur b r i dge c o n s i s t s o f two su lphu r a l o n e

i n s t e a d o f one. A few of them have been i d e n t i f i e d i n

t h e low molecu la r range ( d i t h i a b u t a n e to d i th iahexane) ,

Thiophene can be de sc r i bed as an unsa tu r a t ed 5-

membered r i n g compris ing one su lphu r and f o u r carbon

atome. Thiophenes themselves a r e g e n e r a l l y very s c a r c e

b u t benzo th iophene, dibenzo th iophene and benzoanphtho-

th iophene (compris ing one th iophene r i n g and I , 2 o r 3

benzene r i n g s r e s p e c t i v e l y ) a r e impor tan t c o n s t i t u e n t s

of a l l h igh su lphu r c rude o i l s . a

1.3.9 N i t r o ~ e n Compounds i n Crud0 O i l

The n i t r o g e n con t en t of crude o i l s i s u s u a l l y much

lower than t h e su lphur con t en t ; about 90% of t he c rudes

2-bu tane th io l T h i o l s

J

e t h y l th iophene

( 2- &hyl th iophene)

d imethyl dibenzo thiophene,,

me thy1 benzo th iophene

( 2-methyl benzo(b) th iophene)

2 , F d i m e t h y l d ibenzothiophene I F i g u r e 11: Examples o f Su lphur Compounds i n Crude O i l s

24

conta in l e s s than 0.2$ of n i t rogen by weight. The

average value of crude o i l i s 0.094% by weight. The

l a r g e s t conten ts a r e known i n c e r t a i n crude o i l s from

C l i f o r n i a e.g. 0.65% i n Wilmington and 0.75% i n Gato

Ridge o i l s . 23 Due to a r e l a t i v e minimum of the d i s t r i -

but ion c l o s e to 0.25% we can d i s t i n g u i s h high-nitrogen

crude o i l s ( N 0.25%) from normal. n i t rogen - poor

petroleum, Degraded aepha l t s a r e enriched i n Nitrogen

a s the r e l a t i v e p a r t o f r e s i n e and asphal tenes i s b

increaeed.

The main p a r t o f n i t rogen i s found i n high mole-

c u l a r weight and high b o i l i n g po in t f r a c t i o n s as shown

i n t a b l e VII. These high molecular weight s t r u c t u r e s

containing more o r l e s s at random d i f f e r e n t heteroatoms

N,S,O*

Table VII : Nitrogen Content According to D i s t A l l a t i o n

F rac t ions , Wilmington, Ca l i fo rn ia Crude O i l

Boi l ing range $ Nitrogen w t . 5

350 - 400 400 - 500 Residium

1.3.10 Qxyaen Compounds i n Crude O i l I

I

The t o t a l amount o f combined oxygen i n crude o i l s

i s r e l a t i v e l y low v a r y i n g from t r a c e s t o a maximum o f

2 p e r c e n t by weight. The commercially impor tan t a c i d i c

components o f pe t ro leum commonly termed naph then ic

a c i d s be long t o t h i s group. The oxygen c o n t e n t inc rea -

s e s wi th t h e b o i l i n g p o i n t o f a f r a c t i o n , t h e g r e a t e r

p o r t i o n of oxygen c o n t a i n i n g c o n s t i tuen t s b e i n g concen-

t r a t e d i n t h e r e s i d u a l o i l s with v a l u e s as h igh as 8 b

p e r c e n t b e i n g recorded. 24 I n t h e low and medium

b o i l i n g range d i s t i l l a t e f r a c t i o n s , oxygen i s mainly

p r e s e n t i n t h e form o f c a r b o x y l i c a c i d and t o a l i m i t e d

e x t e n t , phenols .

The i d e n t i t i e s o f c a r b o x y l i c a c i d s p r e s e n t i n c rude

o i l s have been t h e s u b j e c t o f i n v e e t i g a t i o n f o r more

than a century . Naphthenic a c i d s i d e n t i f i e d i n c rude

o i l s i n c l u d e t h e fo l lowing , 24

w 1 c 0 ; H 2,6,10114-tetramethyl pen tadecano ic a c i d

2 ,2 ,6- t r imethyl cyc lohexy l a c e t i c a c i d

3,-ethyl-4-me thy1 c y c l o p e n t y l a c e t i c a c i d

1.3.11 High Molecular Weight N,S,O Compounds

These a r e p r e s e n t i n t h e a s p h a l t i c residuum which

remain a f t e r removal o f d i s t i l l a b l e m a t e r i a l s from t h e

c rude o i l , and r e f e r r e d , t o a a r e s i n s and a s p h a l t e n e s .

The residuum mainly comprises v e r y heavy o i l s , r e s i n s , 4

a s p h a l t e n e s and high molecu la r weight wares. Addi t ion

o f l i q u i d propane a t t e m p e r a t u r e s below 2 1 ' ~ c a u s e s

t h e r e s i n s and a s p h a l t e n e s t o p r e c i p i t a t e and t h e s e

can. t h e n be s e p a r a t e d by d i s s o l v i n g t h e r e s i n s i n

n-p?ntane. The a a p h a l t e n e s a r e .dark-bro wn b lack

amorphous s o l i d s ; r e e i n s a lways seem t o be more abun-

d a n t t h a n a s p h a l t e n e s and t h e r a t i o v a r i e s c o n s i d e r a b l y

depending on t h b c rude o i l s o u r c e e.g. w t $ abundances

f o r r e s i n ( R ) and a s p h a l t e n e s ( A ) i n E l l e n b u r g e r (w.

Texas) , Wilmington ( C a l i f o r n i a ) , Khavday (USSR) and

Boscan (Venezuela) a r e 4.2R. 0.24A; I.4R, 5A; 33R. 8A

and 29R, I 8 U r e s p e c t i v e l y . &bout h a l f o f t h e t o t a l

combined n i t rogen a n d s u l p h u r p r e s e n t i n c rude o i l

a p p e a r s i n t h e form of h e t e r o c y c l i c groups.

1.3.12 O r ~ a n o m e t a l l i c Compounds

Numerous t r a c e e lements have b een d e t e c t e d i n crude

o i l s be s ide6 n i t r o g e n , oxygen and su lphu r which a r e on ly

t o be expected when one c o n s i d e r s t h e h i s t o r y o f pe t ro -

leum from o r i g i n t o well-head. The metals p r e s e n t

i n c l u d e aluminium, barium, calcium, chromium, copper,

go ld , i r o n , l e a d , m a g n e s s i u , manganese, n i c k e l , s i l v e r ,

t i t an ium, vanadium, e t c . bu t n i c k e l a n d vanadium are t h e

most abundant i n the form o f pe t ropo rphy r ina and r e l a t e d

complexes and s t r u c t u r e s y e t t o be i d e n t i f i e d appear t o

be p r e s e n t i n a l l crudes .

The i r c o n c e n t r a t i o n s va ry from sou rce t o source;

t o t a l w o u n t s r ang ing from Ippm t o an exces s I3OOppm.

1.4 Phys i ca l Methods of k n a l y s l n g Crude O i l s 26

c rude o i l and i t e f r a c t i o n s , on d i s t i l l a t i o n ,

cou ld be t e s t e d u s i n g t h e f o l l o w i n g phys i ca l methods.

V i sco si t y

V i s c o s i t y o f a c rude o i l depends most ly on t he

con t en t o f heavy c o n s t i t u e n t s of petroleum r e s i n s , and

aaphal tenee . The v i s c o s i t y o f crude could be measured

u s i n g a Redwood Yiscometer.

1.4.2 F lash P o i n t

The f l a s h p o i n t i s t h e temperature t o which t h e o i l

must be heated i n a s tandard ins t rument t o g ive an inf lamable

mixture wi th a i r and under t h e p r e s c r i b e d condi t ions . The

Pensky-Marten appa ra tus i s used f o r f l a s h p o i n t above 5 0 ' ~

i n J3ritain and Abel appara tus i s used f o r more v o l a t i l e

o i l s wi th f l a s h p o i n t s below 50'~.

I

1.4.3 ' Cloud P o i n t

The cloud p o i n t i s t h e temperature a t which a haze

o r c loud p o i n t f i r s t appears i n a sample of o i l when cooled

i n a p resc r ibed manner. The o i l sample i s dehydrated and 4

f i l t e r e d a t a temperature 7 2 5 ' ~ (above t h e a n t i c i p a t e d

c loud poin t . I t i s then p laced i n a t e s t t ube and cooled

p r o g r e s s i v e l y i n a c o o l a n t held a t -1 t o +2%; -18 t o -20 '~

and -35 t o - 3 2 ' ~ respec t ive ly . The sample i s inspec ted

f o r c l o u d l i n e s s a t temperature i n t e r v a l s of loco

1.4.4 Anil ine P o i n t

Ani l ine p o i n t i s t h e temperature a t which m o i l i s

completely misc ib le wi th an gqual volume of a n i l i n e .

I t i s an approximate measure of aromatic con ten t of a

mixture of hydrocarbons.

1.4.5 S p e c i f i c Grav i ty

Spec i f i c e r a v i t y i s t h e r a t i o of the? d e n s i t y of a

substance t o t h a t of water a t ttle same temperature

about 15 '~ . This is measured u s i n g s p e c i f i c g r a v i t y

b a t t l e o r hydrodeter .

American Petroleum I n s t i t u t e ( A P I ) grav i t y .

The s p e c i f i c g a v i t y o f an o i l i n t h e U.S. i a expreseed

a s degree8 API.

UP1 g r a v i t y - 141.5 - 131.5 ~ p . gr. at 6 o 0 ~ ( 1 5 . 5 O ~ )

S p e c i f i c g r a v i t y i n d i c a t e s t he type of hydrocarbons

p r e s e n t i n t h e crude o i l , The s p e c i f i c g r a v i t y o f

a roma t i c s i s h ighe r than t h a t o f t he p a r a f f i n s .

1.4.6 Wax and Pour Po in t

Wax . , c o n t e n t s o f crude o i l s can range from l e s s than

0.5% to as h igh ae 40. - 50% but very low and very high

wax c o n t e n t s a r e rare.

Crude o i l s with h igh molecular weight A-alkanes

(> n - C ) have high wax o r p a r a f f i n wax amd may 20

con ta in a l s o i so -a lkanes and a lkyl-cycloalkanes . Crudes

of h igh wax .content and hence high pour p o i n t cause

hand l ing problems i n t a n k e r s and p i p e l i n e 8 and such

c rudes r e q u i r e h e a t i n g before d i scharge from t a n k e r s and

heated a t o r a g e i n t h e r e f i ne ry . When t r anspo r t ed by

p i p e l i n e s t o i n - l a d r e f i n e r i e s , they must be d i l u t e d

wi th l e s s waxy crudes .

Petroleum ~ e f i n i n ~ "

R e f i n i n g i n v o l v e a two major branches ; s e p a r a t i o n

p r o c e e e and convers ion p rocesses .

D i s t i l l a t i o n p r o c e s s p r o v i d e s a s u i t a b l e means f o r

s e p a r a t i o n of pe t ro leum compounds i n t o s a l a b l e f r a c t i o n s .

To improve t h e q u a l i t y o f t h e c rude p r o d u c t t h u s obta ined,

aorne chemical o r h e a t t r e a t m e n t o f t e n f o l l o w s d i s t i l l a -

t i o n process .

I n t h e i n d u s t r y c rude o i l i s p r e h e a t e d by d e s a l t i n g ,

a d d i n g o f c a u s t i c soda and i n j e c t i o n o f ammonia b e f o r e

d i s t i l l a t i o n commences. There are- f o u r t y p e s of d i s t i -

l l a t i o n : l i g h t o i l d i s t i l l a t i o n ; a tmospher ic d i s t i l l a t i o n

o f c rude o i l , vacuum d i s t i l l a t i o n and s p e c i a l p roduc t

d i s t i l l a t i o n . 8

I

Table V I I I : P r o d u c t s of Crude O i l D i s t i l l a t i o n U n i t

i n Petroleum R e f i n e r y

F r a c t i o n s B o i l i n g ranRe(Oc) $ Volume Fue l A p p l i c a t i o n

Cases CH c ~ H ~ ~ cjaB,

2.5 Refinery Fue l and LNG

S t r a i g h t run Up to I 4 5 18.2 Gaso l ine

Naphtha I 4 5 - I85 7.5

Kerosene I 8 5 - 240 10.3

Cae a i l 240 - 350 19.9

Resi due 350 41.6

Motor Gaso l ine blending(1ow o c t a n e )

Motor Gasolhne b l e n d i n g A f t e r reforming

8

J e t f u e l , Domestic f u e l , T r a c t o r f u e l

Diese l f u e l , c e n t r a l h e a t i n g g e n e r a t o r s e t c .

Vacuum d i s t i l l a t i o n feed.

1.5.1 Atmospheric D i s t i l l a t i o n o f Crude O i l

D i s t i l l a t i o n o f c rude o i l under a tmospher ic condi-

t i o n e tsrkes p l a c e i n a pr imary tower t a k i n g on ly an ,

overhead p roduc t of a gas and g a s o l i n e . I n t h e secondary

tower, d i s t i l l a t i o n o f t h e lower bottom t a k e s p l a c e t o

g i v e normal a tmospher ia d i s t i l l a t e s up t o heavy gas o i l .

D e s u l p h u r i s a t i o n o f a l l l i g h t e r p r o d u c t s from t h e d i s t i -

l a t i o u n i t .

4 t o t a l overhead p r o d u c t ( f r e q u e n t l y i n c l u d e d i n t h e

ke rosene b o i l i n g range) i s taken, condensed and s e n t t o I

' t h e h i s t i l l a t e hydrot rea tmen t (DHT) r e a c t i o n . The reac-

t i o n p r o d u c t s a r e then s e p a r a t e d and f u r t h e r d i s t i l l e d

i n t o t h e v a r i o u s p roduc t s . b

S i n c e motor g a s o l i n e i s t h e most d e s i r e d p roduc t

from t a b l e V J I I , a r e f i n e r users many p r o c e s s e s t o con- , . .

v e r t t h e r e s i d u e , k e r o s i n e , naph tha t o g a s o l i n e . The

p r o c e s s i n c l u d e s convers ion o f f r a c t i o n s l i g h t e r than

g a s o l i n e through t h e p r o c e s s o f i rsomerisafion a l k y l a t i o n :

convers ion o f f r a c t i o n s i n t h e g a s o l i n e b o i l i n g range

through c a t a l y t i c reforming; convers ion o f t h e f r a c t i o n s

h e a v i e r than g a s o l i n e through vacuum d i s t i l l a t i o n ,

c a t a l y t i c c r a c k i n g and h y d r ~ c r a c k i n ~ .

I. 8.2 I s o m e r i s a t i o n P r o c e s s

I s o m e r i s a t i o n i s used t o c o n v e r t s t r a i g h t c h a i n

bu tane i n t o methyl propane and to c o n v e r t s t r a i g h t c h a i n

hexane and pen tane i n t o branched cha in a l k a n e s t o improve

r a t i n g o f h igh v o l a t i l e ga so l i ne . A c a t a l y s t f o r t h i s

p r o c e s s i s aluminium c h l o r i d e and t he p rocesa may be

accompanied i n t h e l i q u i d o r vapour phase. Temperature

m d p r e s s u r e a r e g e n e r a l l y moderate; about I 5 0 - 1 9 0 ' ~

and . 20 - 30 a t m . The feeds tock i s desu lphur ieed f i r s t

b e f o r e r e a c t i o n can proceed. When t h e r e a c t i o n t a k e s

p l a c e , t h e p r o d u c t s a r e sopara tod by d i s t i l l a t i o n and

molecu la r s i eve .

Equations f o r t h e r e a c t i o n

8 CqH* + HCL + U C l 3 C4Hg + I L l C l Y

CH3CH2CB2CH3 + A I C 1 ° Q

. 4. 8-9 0 CH3-CH CH-CH3 + ~'fA1~1;

*-I i somer i sa t ion

I .'5.3 C a t a l y t i c U l k y l a t i o n

I n a l k y l a t i o n , l i g h t gaseous hydrocarbon o l e f i n s C 3

, and .C and naph tha a r e combined i n t o l a r g e r molecu les 4

- with molecular weight. equa l t o t h e sum of t h e r e a c t a n t s .

C a t a l y s t s used a r e s u l p h u r i c a c i d o r hydrogen f l o u r i d e .

The l i n e a r a l k y l a t i o n p l a n t i n Kaduna u s e s s u l p h u r i c

a c i d as c a t a l y s t ,

1.5.4 C a t a l y t i c Reforming

C a t a l y t i c reforming i s a p r o c e s s o f upgrading t he

I o c t a n e number of gaso l ine . Th i s p r o c e s s is used i n t h e

p roduc t ion o f g a s o l i n e and p roduc t i on o f aromat ics .

The feeds tock i s naphtha i n t h e b o i l i n g r a g e o f 75 - *

1 9 0 ~ ~ . Naphtha c o n t a i n s alkane, aromatic+ c y c l o a l k a n e t ~

The h ighe r p ropo r t i on of cyc loa lkanes i n naphtha, t h e

more s u i t a b l e f o r c a t a l y t i c reforming, The c a t a l y s t

f o r t h e p roce se i s a . m e t a l ( p l a t i n i m or p i e l l a d i m ) w i t h

a c i d i c conponents made up o f H C 1 suppor ted on alumina.

P u r i f i c a t i o n of t h e feeds tock removes atoms of 3,

N , 0 and m e t a l l i c impur i t i e s . C a t a l y t i c reformfng

r e a c t i o n s i n c l u d e dehydrogenation, i ' somer i sa t ion ,

c y c l i a a t i o n , hydrocracking and hydroa lky la t ion .

I. 5.5 , c a t a l y t i c Crackinq

I Catalytic cracking p r o v i d e s a better y i e l d o f

1 g a s o l i n e of much h ighe r anti-knock p r o p e r t i e s ,

C a t a l y s t s such as n a t u r a l o r a r t i f i c i a l c l a y s (0.g.

b e n t o n i t e and montmori l loni t e a c t i v a t e d by s u l p h u r i c

a c i d o r s y n t h e t i c s i l i c a t e s ) are used. The c a t a l y s t

i s u h i l i s e d t o d i r e c t t h e c r ack ing o f a l kanes i n t o t h e

cor responding a lkenes . Naphthalenes are cracked to

a l k e n e s and a lkanes . Aromatics a r e l a r g e l y i n e r t bu t

a hall p ropo r t i on forms coke on t h e c a t a l y s t . Cracking

at lower t empera tu res produce g a s o l i n e 6 r e l a t i v e l y low

i n o l e f i n con t en t ; whi le c r ack ing a t h ighe r t empera tu res

produce o l e f i n ? aad a roma t i c s i n l a r g e volumes. I

1.6 Methods o f Analys ing Petroleum

S e p a r a t i o n be fo r e a n a l y s i s i n v a r i a b l y i s t h e b e s t

approach i n o b t a i n i n g d e t a i l e d d i a r a c t e r i z a t i o n data .

Eventhough i t i s t ime consuming, s u i t a b l e f r a c t i o n s f o r

a d e t a i l e d composi t ional s tudy c& be p repared by u s i n g

a s e r i e s of p rocedures t h a t r e q u i r e inexpens ive labora-

t o r y equipment.

F r a c t i o n a l d i s t i l l a t i o n technique, which p rov ide

so much in format ion on t h e c o n s t i t u t i o n o f t h e d i s t i l l a t e s

of lower b o i l i n g p o i n t , have been s t e a d i l y rep laced by

g a s - l i q u i d chromatography, a more e f f ec t i u e d e v i c e f o r

t h e super f r a c t i o n a t i o n o f micro-samples. ~ h e s e two

t e a h n i q u e s s e p a r a t e t h e c o n s t i t u e n t compounds i n o r d e r

o f b o i l i n g p o i n t s , I

E l u t i o n a d s o r p t i o n ( l i q u i d - s o l i d ) chroaatography

i t s u sed e x t e n s i v e l y at a l l s t a g e 8 o f petroleum separa-

t ion . T h i s t echn ique s e p a r a t e s t h e compound t y p e s i n

o r d e r o f p o l a r i t y ; i t s scope and v e r s a t i l i t y cou ld

however, be much improved i f 8 cimple and e f f e c t i v e b

d e t e c t i o n system becomes a v a i l a b l e , T h i s development

may p e r h a p s be accompliahed i n c o n j u n c t i o n wi th t h e u s e

o f super c r i t i c a l f l u i d s , Gaseous and l i q u i d hydro-

0 c a r b o n s (up t o bop. 300 C ) are u s u a l l y s e p a r a t e d by g a s

chromatography. The group s e p a r a t i o n o f hydrocarbons can

be c a r r i e d o u t by e l u t i o n o r d i sp lacement a d e o r p t i o n

chromatography on s i l i c a - g e l , a lumina, charcoal. o r

bauxi te . , Occa, a i o n a l l y , t h e most a c t i v e g rade o f

s y n t h e t i c magnesium s i l i c a t e i s ueed. Croup s e p a r a t i o n

i s impor tan t i n t h e r e s o l u t i o n o f n a t u r a l l y - o c c u r r i n g

m i x t u r e s o f hydrocarbons from pet ro leum, as f o r example

i n t h e a n a l y s i s o f t h e C 18- CaZ5 pet ro leum f r a c t i o n 28

shown i n f i g u r e I11 below,

I n a t y p i c a l experiment, 8 l i t r e s of petroleum

f r a c t i o n were d i l u t e d wi th an equa l volume of 2,2,4-

t r i -methyl pentane and app l i ed to a colunn (45cm x 2Q:d s i l i ca ge l .

packed with 1 P a r a f f i n s and c y c l o p a r a f f i n s were - e l u t e d with 2 ,2 ,4- t r imethyl pentane, a romat ics were

e l u t e d with benzene and t h e remaining subs tances were

washed o f f t h e column wi th 2-propanol. The a romat ic

compounds were then chromatographed on alumina and

s epa ra t ed by e l u t i o n wi th benzene. * On s i l i c a - g e l , i t i s p o s s i b l e t o s e p a r a t e o l e f i n s ,

p a r a f f i n s , cyclo-paraf f i n s and aromat ice ; mono-olefina

from d i - o l e f i n ~ ~ ~ ; mono-olafins from aromatic*; and

some a c y c l i c mono-olefins from c y c l i c mono-olef i n s .

I n a t y p i a a l displacement s epa ra t i on , 18Og of s i l i c a - g e l

( g r a i n s i z e 0.043 t o 0.075rnm) were poured i n t o a tube

I25cm l o n g w i t h an i n t e r n a l d iameter of 2cm f o r t h e top

50cm and Icm f o r t he rest. The gel w a s added i n p o r t i o n s

and packed uniformly by tappjng t h e tube with a rod. The

a m p l e volume w a s f i x e d accord ing t o i t e c o n t e n t s o f

a romat ics ( t h e column would r e t a i n one s i x t h o f i t s own

weight of a romat ics ) . The sample was added under a

p r e s s u r e of about 0.3 atmoepheres, a s h o r t l a y e r o f

s i l i c a gel was added ( I - 2cm) and then t h e column was

e l u t e d wi th methanol , e thano1 ,o r i s o p r o p a n o l under t h e

eame p r e s s u r e . The f low-ra te was about 20 - 30m1 per

hour and samples of 3 - 5ml were c o l l e c t e d and t h e i r

r e f r a c t i v e i n d i c e s measured.

Petroleum f r a c t i o n c o n t a i n i n g hydrocarbons 100%

I I /Adsorption o n silica-gel 1

1 1 cyc lopra f f i n s

1 I

Aromat ics GQromatics n-paraf f i n s Branched w i t h two wi th one 17.92 and c y c l o

p a r a f f i n s . 50.3s

I

C r y s t a l l i z a t i o n C

Fig. 111 : - S e p a r a t i o n p a t t e r n f o r Petroleum F r a c t i o n

1.6.1 A n a l y t i c a l Methods f o r t h e F r a c t i o n s

I n s e l e c t i n g an a n a l y t i c a l approach, c a r e f u l consi-

d e r a t i o n muet be given to t he h i s t o r y of the sample, i t s

p u r i t y , q u a n t i t y , method of s e p a r a t i o n , a v a i l a b i l i t y of

r e f e r e n c e compounds and c a l i b r a t i n g data and so on.

Phys i ca l t echn iques used over t he y e a r s f o r a n a l y s i s

i n c l u d e i n f ra-red, u l t r a - v i o l e t ab so rp t i on , mass

epectrometry and n u c l e a r magnetic resonance (n.m. r)

e p e o t a s c o p y . b

High-resolut ion mass spect rometry i s inva luab l e as

a f i r s t s t e p i n s t r u c t u r a l a n a l y s i s . Improved methods o f

sample hand l ing with t he d i r e c t i n l e t probe a l low t h e

molecu la r i o n of moet compounds t o be obtained. The

molecu la r formula can be de r ived from t h e ob t a ined

a c c u r a t e mass of t h e molecular ion. These d a t a a r e

ob t a ined on far l e s a sample than would be r equ i r ed f o r

e lementa l a n a l y s i s , and t h e method has t he advantage

of g i v i n g a c r ack ing p a t t e r n , from which o t h e r f e a t u r e s

o f t h e molecular s t r u c t u r e may wel l emerge. An exami-

n a t i o n o f mass s p e c t r a a t h igh and low i o n i e i n g v o l t a g e s

can r e v e a l t h e p resence o f homologous s e r i e s of hydro- ' t h a t

carbon t ypes r e d i f f e r e n t i a t e d between t h e hydrocarbon B

t y p e s t h a t are p r e s e n t ; i t can a l s o r e v e a l t h e i r d i s t r i -

b u t i o n i n t h e mixture.

F i e l d i o n i s a t i o n mass s p e c t o m e t r y i n c r e a s e s t h e

v a l u e o f , mass spec t romet ry i n o r g a n i c a n a l y s i s . The I

I

spectrum o f a complex m i x t u r e i a c o n s i d e r a b l y s i m p l i f i e d

ae t h e r e i s very ' l i t t l e f r agmenta t ion , whi le e t r o n g

molecu la r i o n s a r e o b t a i n e d f o r s a t u r a t e s , such as some

i s o a l k a n e s which under e l e c t r o n bombardment c o n d i t i o n s

may w e l l g i v e v i r t u a l l y no molecular- ion. T h i s new deve- b

1 opment i s c u r r e n t l y be ing used most e f f e c t i v e l y i n labo-

ratories t o s t u d y the composi t i o u o f pe t ro leum waxes. 30

The c o u p l i n g o f g a s - l i q u i d chromatography (g.1.c.)

e s p e c i a l l y when u s i n g c a p i l l a r y columns, wi th high-

r e s o l u t i o n mass spec t romet ry i s a p a r t i c u l a r l y powerful

combination.

1.6.2 Infra-Red Spec t roscopy

I n f r a - r e d spec t roscopy g i v e s ~ t r u c t u r a l in fo rmat ion

about any molecule p r e s e n t i n a compound e s p e c i a l l y wi th

regard t o f u n c t i o n a l groups. The a b s o r p t i o n of i n f r a -

r ed ( I R ) r a d i a t i o n by a molecule g i v e s r i s e to t r a n s i t i o n s

between v i b r a t i o n a l and r o t a t i o n a l energy l e v e l s . T h i s

depends o n t h r e e comdi t i o n s ,

I .

2.

3

and

The f requency o f v i b r a t i o n of t h e molecule must be

equal to the frequency of t h e i n c i d e n t r a d i a t i o n .

The change i n bond l e n g t h o r angle due t o v i b r a t i o n a l

o r r o t a t i o n a l motion must cause a n e t change i n t he

d i p o l e moment of t h e molecule.

The r a d i a t i o n energy must correspond t o t he energy

d i f f e r e n c e o f t h e ground and e x c i t e d states of t h e

molecule.

The I R ab so rp t i on o c c u r s i n t he reg ion 4000 - 20crn-I , 4 t h e s e p a r a t i o n between l e v e l s a r e '10 ~/ rno le . The

concen t r a t i on of t h e sample under examination p l a y s an

impor tan t p a r t i n I R analysis. T h i s i s b e s t summarised

i n Beer-Lambert's l a w which i s

I exp(- E c l ) ...................... ( I )

where I. i s t h e i n t e n s i t y of r a d i a t i o n f a l l i n g on t h e

sample, I , t h a t p a r t t r a n s m i t t e d , C and 1 a r e t h e sample

c o n c e n t r a t i o n s and pa th l e n g t h and E i s t h e abso rp t i on

c o t e f f i c i e n t , which i s a cons t an t f o r a given type o f

t r a n s i t i o n (e.g. r o t a t i o n a l , v i b r a t i o n a l e t c . )

I. 6.3 A p p l i c a t i o n of I n f @Red Spec t ro scop i .

I n f m r e d h a s been used t o i n v e s t i g a t e t h e f u n c t i o n a l

g roups p r e s e n t i n compounds.~ Aromatic compounds are

c h a r a c t e r i s e d by t h e weak C-H s t r e t c h i n g band n e a r 3030cm-1

and by b w d s n e a r I600 and 1500cra-~. The s u b s t i t u t i o n

p a t t e r n on a benzene r , ing can be deduced from t h e s t r o n g

bands a s s o c i a t e d wi th t h e C-H o u t o f p l a c e , bending

v i b r a t i o n 8 below 900crn-~. There are o t h e r bonds i n t h e 8

2000 - I600cm r eg ion which appear as weak ove r tone and

combination bands bu t a r e of l i t t l e u se . The t a b l e I X

shows a b s o r p t i o n of a romat ic compounds.

Tab le I X : shows a b s o r p t i o n o f a romat ic compounds.

Tab le I X : Ubsorpbion of k romat ic compounds i n I r reg ion

Group Band Remark s

Aromatic 3030m Aromatic C-H s t r e t c h i n g *

I600m More i n t e n s e than wi th unconjugated double bonds.

I580m S t r o n g e r when r i n g i s f u r t h e r conju- g a t e d

I500m T h i s i s u s u a l l y t he s t r o n g e s t o f t h e a . - two o r t h r e e bonds.

The two o r t h r e e bonds i n t h e I600 - 1500cm-I r eg ion

a r e shown by most six-membered a romat ic r i n g sys tems

such as benzene, p o l y c y c l i c sys tems and p y r i d i n e s .

They c o n s t i t u t e a v a l u a b l e i n d e n t i f i c a t i o n of such a

systern. F u r t h e r bonds a r e shown by a romat ic r i n g s i n

t h e f i n g e r p r i n t r eg ion between I225 and 950cm-I which

a r e of l i t t l e d i a g n o s t i c value.

I. 6.4 Gas Chromatography

T h i s i s probably t h e

(G.C. )

most u t i l i s e d o f a l l t h e

chromatographic techniques . I n t h e g a s - l i q u i d

chromatography, t h e mobile phase i s a g a s and t h e

s t a t i o n a r y phase is a t h i n l a y e r of n o n - v o l a t i l e

l i q u i d bound to-. a s c l i d suppor t . Desp i t e commercial

v a r i a t i o n s , a l l gas chromatographs c o n s i s t of s i x b a s i c

components namely:

a c a r r i e r g a s which i s main ta ined at a h igh p r e s s u r e

and d e l i v e r e d t o t h e i n s t r u m e n t at a r a p i d and

r e p r o d u c i b l e r a t e .

a sample i n j e c t i o n system,

t h e s e p a r a t i o n column.

one o r more d e t e c t o r s .

5. thermosta ted chambers f o r t h e temperature regula-

t i o n o f t h e column and d e t e c t o r s .

6. an a m p l i f i e r and recQP-1.1

The sample i s i n j e c t e d i n t o p r ehea t ed p o r t s where

i t i s i n s t a n t a n e o u s l y vapo r i s ed and t r a n s p o r t e d as a

p l u g by t h e i n e r t c a r r i e r g a s i n t o t he column. The

s o l u t e components a r e s e l e c t i v e l y p a r t i t i o n e d be tween

t h e mobi le and s t a t i o n a r y phases aid then succe s s ive ly 3s

e l u t e d ae f r e s h c a r r i e r gas i s passed through t h e column. 4

Each s o l u t e at i t s own r a t e forms i t s own chrufilri! .r.~*hir!

band. The sample bands e n t e r t h e d e t e c t o r and t h e da t r -

i s amp l i f i ed , recorded and analysed.

A fundamental measured parameter i n G.C. i s t h e

r e t e n t i o n volume ( v ~ ) which i a t h e volume of carrier

gas r equ i r ed t o c a r r y a band of s o l u t e down the column.

Under any g iven set o f t empera tu res and carrier gas

flow r a t e (PC) , t h e r e t e n t i o n t ime ( t n ) i s r e l a t e d t o

t h e r e t e n t i o n volume by

where F c i s t h e f low rate of c a r r i e r gas.

The e f f i c i e n c y o f a column i; -. ied i n terms

o f t h e t h e o r e t i c a l p l a t e , ( N ) ; t h e l a r g e r t h e number of

t h e o r e t i c p l a t e s , t h e more e f f i c i e n t t h e s e p a r a t i o n .

N can be c a l c u l a t e d from t h e r e l a t i o n s h i p

where V' i s t h e volume of t h e g a s which passed from

t h e appearance o f an a i r r e f e r e n c e peak t o t h e c e n t r e

o f t h e sample peak and W* i s t h e width measured a t t h e

h a l f h e i g h t o f t h e band.

I. 6.5 Nuclear Magnetic Resonance ( N W R ) Spec t roscopy

NMR i e used t o de termine t h e number o f each type

o f hydrogen p r e s e n t , and a l s o to o b t a i n in fo rmat ion

r e g a r d i n g t h e n a t u r e of t h e immediate environments of

each of t h e s e types of hydrogen atom. The n u c l e i o f

atoms p o s s e s s e l e c t r i c a l energy and as t h e n u c l e u s

s p i n a on its axis , t h e motion s e t s up a magnet ic

f i e l d and p roduces magnet ic energy. When a hydrogen

n u c l e u s , s p i n n i n g about i t s a x i s i s p l a c e d i n a magne-

t i c f i e l d , t h e magnetic energy o f t h e n u c l e u s cause8

i trs own f i e l d t o a l l i g n wi th t h e e x t e r n a l f i e l d which

e x e r t s a to rque upon t h e n u c l e u s and i t assume6 a

pe rmi t t ed o r i e n t a t i o n wi th r e s p e c t to t h i s e x t e r n a l

f i e l d . . The system i s q u a n t i 2 e d .

Thirs number of p o s s i b l e o r i e n t a t i o n s i s determined

by I , the apin number of t h e nucleus. Any one 21 i 'I

or ien ta t iona is poss ib le . Since t he s p i n number o f

hydrogen I = k, this n u c l e u s w i l l assume only one of

two (2(* ) + 1 ) p o s s i b l e o r i e n t a t i o n s each of which

cor responds t o a pe rmi t t ed energy l e v e l . 32

Whereae p o s s i b l e o r i e n t a t i o n s assumed by a nuc l eus +

i s determined by I , t h e a c t u a l e n e r g i e s a r e determined

by t h e magnetic moments, A. I I

The d i f f e r e n c e i n energy between t he two quantum

l e v e l a o f hydrogen n u c l e u s depends on t h e a p p l i e d

magnetic f i e l d and' the magnetic moment of t h e nucleus .

I t i s expressed as

where H is t h e a p p l i e d magnetic f i e l d and, I , t h e 0 .

s p i n quantum number.

The width of a b s o r p t i o n l i n e i n t h e nmr spectrum

i s determined by t h e magnet ic f i e l d a t r e q g t h and t h e

l e n g t h o f time t he e x c i t e d n u c l e u s remains i n t h e e x c i t e d

s t a t e . The width o f t h e abeo rp t i on l i n e i s i n v e r s e l y

p r o p o r t i o n a l t o t h e r e l a x a t i o n t i m e . Exc i t ed n u c l e i

may l o s e t h e i r energy, r e l a x , and r o t u r n to the ground

s ta te by e i t h e r

( a ) t r a n s v e r s e r e l a x a t i o n , i n which an e x c i t e d nuc l eus

y i e l d s i t s energy t o an unexc i t ed ne ighbour ing

nuc l eus which becomes exc i t ed . Here t h e r e i s

no n e t change i n energy of t h e system.

( b ) l o n g i t u d i n a l r e l a x a t i o n , where t h e m e r a o f t h e

e x c i t e d nuc l eus i s conver ted t o h e a t with a n e t

i n c r e a e e i n temperature of t he system.

S t r u c t u r a l e l u c i d a t i o n u : - i ng n.m. r. i n v o l v e s tklu

change i n ab so rp t i on frequency " .*Lined hydi.ogen

wi th a chango i n t h e environment o f t he proton. T h i s

i s c a l l e d chemical s h i f t denoted as 6. The e l e c t r o n s

s h i e l d t h e nuc l eus and t h i s s h i e l d i n g i s determined by

t h e e l e c t r o n e g a t i v i t y o f t h e atoms to which t h e p r o t o n s

a r e bonded and w i l l change with t h e number and type o f

atoms p r e s e n t i n a given f u n c t i o n a l group. The problem

a s s o c i a t e d with de te rmin ing t h e f requency o f ab so rp t i on

i s overcome u s i n g t he chemical s h i f t procedure ,

The method i n v o l v e 8 d i ~ s o l v i n g t h e i n t e r n a l r e f e r e n c e

and an unknown enmple i r l the anme solution, subjecting

t h e s o l u t i o n t o t h e same magnet ic f i e l d and t h e differences

i n the f r e q u e n c i e s o f t h e two samples ob ta ined . Te t ra -

methyl-8l lanu (TMS) io commonly used. This compound i s

symmetrical wi t h . 1 2 e q u i v a l e n t hydrogens and yiolds a

single sharp a b s o r p t i o n . l i n e .

The chemical e h i f t 9, which could e i t h e r b e i n

S ( d e 1 t o ) o r 7: ( T a u ) valuen i~ expressed as,

where H and Hr a r e t h e f i u l d s t r e n g t h 8 o f t h e sample; 8

and r e f e r e n c e r e s p e c t i v e l y .

1.6.6 A p p l i c a t i o n of Nuclear Magnetic Resonance

NMR hydrogen s p e c t r a are p a r t i c u l a r l y u s e f u l i n

orgcwiic s t r u c t u r a l .&ysi s f o r r e v e a l i n g i n f o r m a t i o n

on t y p e s of molecu les wd r e l a t i v e s p a t i a l d i c p o a i t i o n

o f t h e hydroeen atoms w i t h i n t h e molecule. The versa-

t i l i t y and scope o f nmr t echn ique i s be ing enhanced by

t h e o tudy of carbon-13 s p e c t r a at the n a t u r a l l e v e l o f 33

abundmce. V e r c i e r , P. &. uood a method b a ~ e d on

13c NMR wi th t h e u s e o f F o u r i e r t ransform techn ique t o

determine t h e a romat ic carbon con t en t of any petroleum

c u t and crude o i l s . The method i s s e n s i t i v e and fast

as compared with t h e con t inuous wave,

Also a s t r u c t u r a l a n a l y s i s o f crude o i l f r a c t i o n s

based on NHR, I R , n-d-rn and u r e a e x t r a c t i o n methods was

c a r r i e d o b t by Nagai, M -- e t al? The method involved

d i s t i l l i n g t h r e e c rude o i l s at 2 5 0 ' ~ under N , and t h e

24 f r a c t i o n s ob t a ined were s t u d i e d by NHR, I R and n-d-0'

methods, Equa t ions were g iven t h a t c o r r e l a t e t he

amount s of a romat ic p a r a f f i n i c and naph then ic carbon

wi th s h i f t r anges i n t h e NMR spec t r a . These equa t i ons were

used t o s tudy t h e s t r u c t u r a l changes t h a t o c c u r d u r i n g

t h e e x t r a c t i o n of petroleum with f u r f u r a l (98-01-1) and i n . .

a d d i t i o n p u r i f i c a t i o n with u r e a (57-13-6) and t h i o u r e a

NRR s p e c t r a of naph tha lene , anthracene35 and phenan- are

t h r e n e A shown i n f i g u r e s V1 and VIf r e s p e c t i v e l y a t t h e \

appendix.

I, 6.7, u l t r a - ~ i o l e t / ~ i s & i b l e Spect roscopy

A u s e f u l in fo rmat ion from t h e u l t r a - v i o l e t o r

v i e i b l e spectrum o f a compound i s o b t a i n e d when t h e

rave- leng ths o f maximum a b s o r p t i o n ('Amax) * a d i n t e n s i t y

of a b s o r p t i o n a r e measured a c c u r a t e l y , The compound

must be d i s s o l v e d i n some s u i t a b l e s o l v e n t t h a t does

n o t i t s e l f absorb l i g h t i n t h e r e g i o n under i n v e s t i g a -

t i o n , t h e most commonly used s o l v e n t f o r u l t r a v i o l e t

s p e c t r a l d e t e r m i n a t i o n i s 95% e t h y l a l c o h o l ; wa te r and

hexane a r e a l s o commonly used. S h i f t i n g of t h e p o s i t i o n s

o f a b e o r p t i o n p e a k s o c c u r when d i f f e r e n t s o l v e n t s a r e b

ueed, The X m a x f o r non-polar compounds i s g e n e r a l l y

t h e same i n a l c o h o l and hexane; the.>max f o r p o l a r

compounde i s u s u a l l y s h i f t e d .

The s o l u t i o n must be p laced i n some s u i t a b l e

c o n t a i n e r t h a t i s t r a n s p a r e n t t o l i g h t i n t h e r e g i o n

b e i n g s tud ied . S i n c e g l a s s a b s o r b s u l t r a - v i o l e t l i g h t

s t r o n g l y , q u a r t z c e l l s must be used wi th a p a t h l e n g t h

of 1 .Ocm. The most s u i t a b l e source o f l i g h t i n t h e

u l t r a - v i o l e t r e g i o n ( I 8 0 - 400mp) i s t h e hydrogen

d i s c h a r g e lamp. Most s p e c t r o m e t e r s a r e double-beam

ins t ruments . The primary source of l i g h t i s s p l i t i n t o

two beams, one o f which p a s s e s through a c e l l c o n t a i n i n g

t h e re f crence solvent, The spectrophotorneter e l e c t r i -

c a l l y sub t r ac t s t h e absorption of t h e solvent i n t h e

reference beam from t h e absorption of t h e so lu t ion i n

t h e sample beam. Thus e f f e c t s owing t o absorption of

l i g h t by the solyent a r e minimized, I

Most recording spectrophotometers record wave-

l e n g t h versus absorbance. The absorbance A o r o p t i c a l

dens i ty i s given by

. where I, i s t h e i n t e n s i t y of i nc iden t l i e h t and I i s

t he i n t e n s i t y of t ransmit ted l i g h t , The ranAe of

absorbance commonly recorded i s 0 - 2.0. The i n t e n s i t y

of absorption band is ca lcu la ted usina Beer-Lam ber t ' s law, which can be formulated by t h e relati 'onship

A . . . . . o . . i . . . . . . . * . . . * . . . . . . ( 7)

where 6 i s t h e absorpt iv i ty ; C: i s the molar concentrat ion

( m ) and 1 is t h e p a t h l e n g t h i n centimeters.

The u l t r a -v io l e t region i s e s s e n t i a l l y 200 - 400 nm

and t h e v i s i b l e reaion i s 400 - 700 nm. However, t h e

overlap i s between 340 - 400 nm. Charge t r a n s f e r

t r a n s i t i o n involve an intermolecular o r an i n t e r i o n i c

r ed i s t r i bu t i on of charge whereby an e lec t ron o r a

f r a c t i o n of an e lec t ron i s t r ans f e r r ed from one ion o r

molecule t o another ion o r molecule i n t h e same species,

The absorption of l i g h t energy by o r ~ a n i c compound

i n t h e v i s i b l e and u l t r a -v io l e t region involves promotion

of e lec t rons i n 6, n, and n-o rb i t a l s from t h e ground

s t a t e t o higher energy s ta tes . These higher energy s t a t e s

a r e described by molecular o r b i t a l s t h a t a r e vacant i n t h e

ground s t a t e o r unexcited s t a t e and a r e commonly c a l l e d

anti bonding o rb i t a l s . The anti- bonding o r b i t a l associa ted

with t h e 6 bond i s ca l l ed 6 o r b i t a l and t h a t associa ted

w i t h II-bond i s c a l l e d t h e fl.*

The e lec t ron ic t r a n s i t i o n t h a t a r e involved i n t h e ,

u l t r a -v io l e t and v i s i b l e regions a r e of t h e following

1.6.8 Application of Ultra-Violet Spectroscopy

Aromatic compounds absorb i n t h e u l t r a -v io l e t region

w i t h varying i n t e n s i t i e s , example benzene absorbs s t rongly

a t 184 mu ( A 47,000) and 204 ( 27,500) and 254 ( 5210) i n

cyclohexane.

The t a b l e below shows t h e absorption band i n t h e

U V - r eg ion o f some a roma t i c compounds.

Table X: lQbsorption o f k roma t i c s i n t he UV-Region

Hydro carbon ~ a n d s ~ ~

;h max Y m a x /7 max

Naphthalene 220 (100,000) 275 ( 5,700) 312 (250)

Phenanthrene 252 ( 50,000) 293 (16,000) 330 (2509

Naphthacene 278 (200,000) 474 (13,000) -

pentacene 310 (270,000) 580 (15,000) -

I n conjugated systems, t h e more t h e number o f double

bonde t h e h ighe r t h e Ymax and smax. 38

Higashi -- e t al . u s e d h igh speed gel permeation

chromatography with uv spec t rome t r i c d e t e c t i o n to

c h a r a c t e r i s e , analyse and i d e n t i f y seven t ypes o f pe t ro-

leum o i l s . The p r o c e s s i n v o l v e s i d e n t i f y i n g petroleum by

t h e r e t e n t i o n time-abaorbance (240 - 400nm) diagram of

t h e e l u a t e of h igh p e r f o nuance-li quid chromatography with

I. 7 SEPlARBTION TECIINI QUE

I .7.I S i l i ca -Gel Column Chromatography

Column adso rp t i on o r e l u t i o n chromatography s e p a r a t e s

subs t ances accord ing t o t h e i r r e l a t i v e p o l a r i t i e s .

Adsorpt ion of molecules on t h e s u r f a c e o f t h e adsorbent i s

r e s a t e d t o i n t e r a c t i o n of adsorbent and adsorbed molecules.

The l e s s adsorbed compoundsmove downward more qu ick ly than * ' 1

t hose adsorbed more s t r o n g l y and o f t en complete s e p a r a t i o n b

i s achieved. S i l i c a - g e l is t h e most f r e q u e n t l y used

adsorbent f o r s e p a r a t i o n o f unsa tu r a t ed and s a t u r a t e d

hydrocarbons. When s i l i c a - g e l i s hea ted up t o about

0 I50 C format ion of a d d i t i o n a l f r e e hydroxyl adso rp t i on

si t e e h icreases , t h e adso rp t i on energy, maximum s u r f a c e

a c t i v i t y appears t o be achieved a f t e r about 4 hours a t

P a r a f f i n i c and naphthenic hydrocarbons are more

adsorbed on s i l i c a - g e l than a r e t h e unsa tu r a t ed components.

The a d s o r b a b i l i t y i s a l s o i n f l uenced by o t h e r s t r u c t u r a l

f a c t o r e e.g. molecular weight, shape o f t h e molecule and

t he number of s a t u r a t e d r i n g s p resen t . The more c y c l i c

t h e molecule; , t h e more s t r o n g l y i t i s adsorbed, however,

t h e d i f f e r e n c e i n a d s o r b a b i l i t y o f p a r a f f i n s and naphthenea

i s u s u a l l y f a r sma l l e r than t h a t of naphthenea and

8 r 0 U I a t i C ~ .

MA^ and ~ o r z i a t i ~ ~ s epa ra t ed o i l f r a c t i o n s by means

o f chromatography and achieved t h e s e p a r a t i o n by washing

t h e sample o v e r s i l i c a - g e l wi th l a r g e q u a n t i t i e s of s o l v e n t s

which removed all t h e p a r a f f i n s and naphthenee. ~ i ~ t ' m

e t ale4' modif ied t h i s method f o r t h e de t e rmina t i on o f -- a r o n a t i c e i n hydrocarbon mix tu ree b o i l i n g above M O O ~ w$th

accuracy o f about I$.

I .7.2 Thin Layer ~h roma toq raphy (T .L .~ . )

Thin l a y e r chromatography (T.L. C. ) i s one o f t he most

popu la r and widely used s e p a r a t i o n techniques . The r ea sons

f o r t h i s i n c l u d e ea se of use , wide app l i c a t i . on t o a g r e a t

number o f d i f f e r e n t samples, h igh s e n s i t i v i t y , speed o f

s e p a r a t i o n and r e l a t i v e l y low cost.

I n TLC, uniform t h i n l a y e r s of aorbent o r s e l e c t e d

m e d i a are used as a c a r r i e r medium. The so rben t i s a p p l i e d

t o a backing as a c o a t i n g t o o b t a i n s t a b l e l a y e r of s u i t a b l e

s i z e . The most common suppor t i s a g l a s s p l a t e , but o t h e r

s u p p o r t s such as p l a s t i c s h e e t s and aluminium f o i l are a l a o

used. The sorbent most commonly used a r e silica- el G 6 ,

alumina, k i e se lguhr (diatomaceous p r t h ) and c e l l u l o s e ,

The s tandard s i z e f o r T.L.C. p l a t e i s 20 x 20crn.

Cther p l a t e s i z e s used a r e 5 x 20 cm and 20 x 40 cm;

%ic ro l ' p l a t e s have been made from microscope s l i d e s ,

The sample t o be separa ted i s app l i ed on t h e l a y e r

1 - 2 cm from t h e end of t h e p l a t e . The p o i n t of

a p p l i c a t i o n i s c a l l e d t h e s t a r t i n g p o i n t o r o r ig in .

With t h e sample s p o t s a t t h e bottom, t h e p l a t e i s p laced

on a s l i q h t ang le from t h e v e r t i c a l i n t o a c losed b

r e c t a n g u l a r t ank c o n t a i n i n g a m o l l amount of t h e mobile t

phase.

The n a t u r e and chemical composit ion of t h e mobile

p h a s e i s determined by t h e type of subs tance t o be

sepa ra t ed and t h e t y p e of morbent t o be used f o r

separa t ion . C a p i l l a r y a c t i o n causes the mobile phase t o

t r a v e l t h r o w h t h e medium i n a p r o c e s s c a l l e d development,

Af t e r t h e p l a t e i s d r i e d , t h e sepa ra t ed s p o t s can be

v i s u a l i s e d i n a number of ways such a s viewing under an

u l t r a - v i o l e t l i g h t o r spraying with' one of t h e wide v a r i e t i e s

of spray in^ r e a g e n t s used i n t h i s l a y e r chromatography. The 'ITLC

procedure can be aunmarised i n t h e f i g u r e below.

The'%-value i s a convenient way t o e x p r e s s t h e

p o s i t i o n of a subs tance on a developed chromatogram.

I t i s c a l c u l a t e d as t h e r a t i o

d i s t a n c e o f compound from o r i g i n R.f E . . . . . (8) d i s t a n c e of s o l v e n t f r o n t from o r i g i n

Rf-valueebetween 0 and 0.999 wi thou t u n i t s are accep t ab l e ,

The d i a t a n c e i s measured to t h e c e n t r e o f t h e sample zone

o r spot . b

If i t i s d e s i r e d t o e x p r e s s p o s i t i o n s r e l a t i v e to I

t'he p o s i t i o n of ano the r aubatance X, t h e R, can be

c a l c u l a t e d :

dhs tance o f compound from o r i g i n Rx - * .... ....( 9)

d i s t a n c e o f r e f e r g n c e compound X from o r i g i n

Values o f Rx g r e a t e r than I a r e p o s s i b l e . -

Rx i s r e l a t i v e r e t e n t i o n value.

Thin l a y e r chromatography can be used ( I ) to simply check

t h e p u r l t y of a substa,rlce, ( 2 ) t o a t t emp t t o s e p a r a t e and

i d e n t i f y t h e components i n a mix tu re o r (3 ) t o o b t a i n a

q u a n t i t a t i v e a n a l y s i s of one o r more of t h e components

p resen t .

Preparation of Sample

\ I

Re lat ive ly pure components I such as phamaaeut i c a l Crude extracts preparations

\ 1 Part i t ion, coPumn or thin layer chromato- graphy

by spot t ing or streaking

4 Development

short, . long, or overrun

.1 Drying of chromatogram

J. Detection - 3.

V i eual , uv scanning, reagent spray

.1 Component removal (Optional)

Documentation

Fig. IV: The process o f thin layer chromatography

TLC has a number of basic advantages over l i q u i d

chromatography (LC). While a methodology can be

developed f o r s p e c i f i c separat ion, TLC uses less

solvent, The p o l a r i t y of t h e solvent o r type of

'solvent mixture can be changed i n a matter of minutes.

I n TLC, a number of samples can be handled a t a time,

~ o s h o f f -- e t a141 coupled TLC w i t h high performance

liquid chromatography (H13Lc), I n t h e technique s o l u t e s

from t h e column were t rans fe r red by mbans of a f i n e

s t e e l c ap i l l a ry tube (0.25m .- 1.0) onto 5 x 20 cer j

chromatoplates t h a t were moying under t h e column a t a

speed of 2cm/min, As t h e p l a t e was being heated, a

m a l l vacuum l i n e was placed above t h e so lu t e zone

t o evaporate t h e e lu t ion solvent. The workers were

a b l e t o de t ec t 60ng/spot, and w i t h t h e chlor ina ted

p e s t i c i d e methoxychlor, 0,6ng/spot, A spectro-

flourirncter was used f o r de tec t ion a f t e r t h e production

of f lourescen t de r iva t i ve s i n s i t u ,

I .7.3 Paper Chromatography

A s e p a r a t i o n by pape r chromatography i s ach i eved

by p l a c i n g a drop of t h e t e s t s o l u t i o n (e.g. 0.02ml)

n e a r one end o f a s t r i p o f f i l t e r paper and a s o l v e n t

i o al lowed t o .:move o v e r t h e s t r i p by c a p i l l a r y flow.

The mobile phase i s u su&l ly s a t u r a t e d wi th water t o

p reven t dehydra t ion of t h e paper du r ing t h e s o l v e n t

f low and i t may a l s o c o n t a i n a d d i t i o n a l r e a g e n t s such

as a c i d s , complexing a g e n t s e t c . b

4 s t h e mobile phase t r a v e l s o v e r t h e i n i t i a l sample

spo-t, t h e i n d i v i d u a l s o l u t e s become d i s t r i b u t e d between

t h e moving s o l v e n t and t h e water f i lm r e t a i n a d by t h e

c e l l u l o s e fkbres . Under i d e a l c o n d i t i o n s , t h e components

migra te , a t d i f f e r e n t i a l r a t e s , as zones j u s t s l i g h t l y I 4

larger than t h e o r i g i n a l spot . The f low o f t h e so lven t

i s stopped a f t e r t r a v e l l i n g some predetermined d i s t a n c e

and t h e p o s i t i o n o f t h e s e p a r a t e d s p e c i e s i s l o c a t e d by

v i s u a l i z a t i o n process . This normal ly i n v o l v e s sp r ay ing

t h e paper wi th a reagen t which tau-ses t h e components t o

form a d e r i v a t i v e which i s e i t h e r coloured o r f l o u r e s c e s

when exposed to u l t w v i o l e t l i g h t .

E r n e s t na ly4* used t h e technique of paper chrornato-

graphy t o a n a l y s e p o l y c y c l i c tar hydrocarbons. He used

Whatman No. 4 f i l t e r paper impregnated wi th 1096 p a r a f f i n

o i l and methanol s a t u r a t e d with p a r a f f i n o i l (p repared

by shaking methanol wi th p a r a f f i n o i l i n a s epa ra to ry

funne1)as t h e ascending mobile phase. These were found

s u i t a b l e f o r paper chromatography o f t h e p o l y c y c l i c tar

hydrocarbons. The paper was impregnated by d ipp ing i t

i n t o a 10% pe t ro - e the r s o l u t i o n of p a r a f f i n o i l q u a l i t y . . 6

as i n *pharmacopoea Bohem s l o v e i c a m ( second e d i t i o n ) and

by evapo ra t i ng t h e pet ro-ehher d u r i n g I5 mins.

A f t e r ' deve lop ing t h e chromatogram f o r about 4 hou r s

(30 cm from t h e f r o n t t o t h e s t a r t i n g p o i n t i s s u f f i c i e n t )

i t wats p o s s i b l e t o eee c h a r a c t e r i s t i c f l uo re scence s p o t s

under u l t r a - v i o l e t l i g h t . The average Rf-valuesand t h e i r

c o l o u r s under uv l i g h t , bo th o f c o n t r o l subs tance and of

t h e s p o t s ob t a ined from c o a l tar wi th t h e pheno ls and

n i t r o g e n compounds removed (by shaking a cyclohexane

s o l u t i o n o f t h e tar wi th 2N aq. KOH and a f t e r r e j e c t i n g are

t h e aqueous l a y e r wi th 2 N ~ ~ a 0 & a s shown below.

Table X I : Paper Chromatographic Result o f P o l y c y c l i c

Tar Hgdrocarbons I

Control Rf- F lourescence R f Notes Order compound va lue ( C J ) Coal tar

compound

0,60 I n exce s s on ly

Greenish - 0.50

3 Anthracene 0..43 V i o l e t Phenanthrene

4. Pyrene 0.36 Green

0.44 V io l e t spo t s epa r t i n g # from o l l o - wing green (TI

5 0.34 Blue-v io le t

6 fi Chryeene 0.31 Yellowish-green 0.32 Chrysene(C) p o s s i b l y I , 2-benzan- t hracene ( C J )

7 3.4 Benz-pyrene 0.28 V i o l e t 0.28

8 x 1 ,2 ,5 ,6 Di- 0.254 V io l e t 0.25 1 ,2 ,5 ,6 d i - benzan t h r ene 0.252 Yellowish-green benzoan thra-

cene(C) possi,- b b l ~ 1 ~ 3 ~ 7 , 8 dibenzan- t h r e n e ( ~ , ~ ) t h e 2nd i s concen t r i c wi th t h e 1st (c ) i n excess on ly

Table X I 1 Contd. :

-

Order Cont ro l Rf- F lourescence R f Notes compou~d v a l u e ( C J ) Coal tar

compound

9 V i o l e t 0.21 P o s s i b l y c o r o n e n e ( ~ )

10-1 5 White b l u i ah 0.20 These s p o t s a r e a l w a y s 0.18 so w e l l separa ted(T) 0.16 0.14 0.12 0. I 0

Yellow 0.09 T h i s forms thq 1st of t h e s e r i e s which w i l l be developed i n d i f f e r e n t s o l v e n t systems(T)

r two s p o t s due t o an i m p u r i t y i n t h e c o n t r o l compound.

C = Cont ro l compound .

T - r C o d tar compound

1.8 & n a l y s i s on Niger ian Crude O i l s

I n a v e r y r e c e n t i n v e s t i g a t i o n o f t h e hydrocarbon

types' a n a l y e i s o f petroleum f r a c t i o n s , ~ w a d i n i ~ w e ~ ~ and

- Okoro j i developed nove l e q u a t i o n s t h a t could be used f o r

t h e d e t e r m i n a t i o n o f t h e molar f r a c t i o n s o f t h e a romat ic ,

naph then ic and p a r a f f i n i c c o n t e n t o f t h r e e Niger ian crudes,

ma Iboe l i ~ h t (uL), Brass BLend ( BB) and Trans Niger

p ipe l ine (TNP).

The f rac t ions were sulphonated i n order t o remove

t h e aromatics and th i s was confirmed by the disappearance

i n t h e I R spectra of t h e aromatic C=C a t .+ 1600 cm-'

and 1493 cnol and - C-H between 3000 and 3020 cm-l. 1 I n addition H absorptions around 2 - 472 i n t h e nmr

spectra a l so disappeared, The workers found t h a t TWP

on t h e averaEe contains more pa ra f f in s than QIL and B&

The significance of this work i s t h a t it represents t h e

f i r s t reported hydrocarbon t y p e analysis on Nigerian cruhes,

The use of urea channel complexes i n t h e separation

of s t r a i g h t chain hydrocarbons has been a subject of many

studies. ~ c n g e n ~ ~ f i r s t found t h a t urea forms inclusion

complexes wi th s t r a i g h t chain hydrocarbons having 7 16

carbon atoms.

Recently urea-inclu sion complexes have been

prepared on four Nigerian crudes: QIL, BB, 'lNP and E 45 by Nwadinigwe and Eze . The adducts were decomposed

and t h e n-paraffins analysed by gas chrmatoaraphy and

infra-red spectroscopy. They found t h a t f o r t h ree of

t h e crudes, the maximum hydrocarbon chain lenqth present

was C34.

Anoguk inves t igated t h e appl ica t ion of t h e l i a and

exchange react ion f o r qua l i t a t i ve determination of

aromatics i n petroleum. This was achieved by subject ing

petroleum samples t o t h e ligand-exchange react ion which

l e d t o a se lec t ive complexation of aromatics, The

r e su l t i ng complexes when subjected t o ppro ly t ic mass

spec t ra l analysis , revealed a number of mono-; d i - ;

t r i c y c l i c aromgtic compounds. I n another study,

~ z o g u ~ invest igated t h e p o s s i b i l i t y of f inger-

p r in t ing some Niaerian crude o i l samples through mass b

6 5 spectrometric ana lys i s of t h e i r IT - arene-IT - cyclopentadienyliron hexaflourop hosp hate derivat ives.

Ofodile e t allcg worked on t h e urea adduction of -- n-paraff ins i n kcros6ne (bp 175 - 265O~). They compared

c e r t a i n key p rope r t i e s such as spec i f i c gravity, f l a s h

po in t , smoke point and t h e ASTM d i s t i l l a t i o n p r o f i l e s

of t h e resu l t ing r a f f i n a t e and o r ig ina l kerosene.

Ekwcozor -- c t a149-9-.51 jo in t1 y studied Shsl e samples

and crude o i l s from t h e Niger Delta area, I n t h e

ana lys i s , they were able t o i d e n t i f y t r i t e r - p e n l l d

de r iva t i ve s from Shale samples and Crude o i l s from

the Niger Delta area.

~ z 0 ~ 1 . i ~ analy sed aromatic hydrocarbon content of

va r ious Nigerian crude o i l samples w i t h py ro ly t i c

mass spectrometry, The r e s u l t ind ica ted common

aromatic cons t i t uen t s and low polyaromatic content i n

crudes from t h e Delta areas. b

1.9 A i m o f t h i s p r o j e c t

One of t h e s i t u a t i o n s e n c o u n t e r e d i n crude o i l process-

prgduced in i n s i e t h e red o i s 1 heav i e r f r a c t i o n s pea&lting-- ere

from the a romat ics p resen t . These red o i l s l d e r i v e d mainly

from a r e n i u m b n s o f p o l y c y c l i c a roma t i c s formed by t h e

p ro tona t i on of t h e a romat ic r e s i d u e s by t h e a c i d c a t a l y s t s

used. The magnitude o f ' Ahe .problem bears a d i r e c t r e l a -

t i o n s h i p t o t h e concen t r a t i on o f a romat ics p r e s e n t i n t h e

crude and t o the s t r e n g t h of t he a c i d i c c a t a l y s t used. , Therefore , as a c o n t r i b u t i o n t o a b e t t e r unders tand ing o f

t h e i n h e r e n t p r o p e r t i e s o f Niger ian crudes , t h i s work aims

t o investigate the d i s t r i b u t i o n of t h e aromat ic sub-types

i n t h e h i g h e r b o i l i n g f r a c t i o n a of t h r e e Niger ian well-

head crude o i l s . Knowledge of t h e c l a s s e s of aromat ic

hydrocarbons i n t r i n s i c t o t h e c rudes i s a l s o c r u c i a l t o

r e a l i z a t i o n of how aromat ic petroleum p roduc t s a r e

der ived.

CHAPTER TWO

RESULTS &ND DISCUSSION 2.0

Any- compreheneive rstudy o f petroleum crude o i l s and

t h e i r p roduc t s i s f a c e d with t h e problem of i s o l a t i n g

a romat ic hydrocarbons acco rd ing t o t h e i r number o f

a romat ic r ings . The magnitude o f t h e problem i s depen-

den t on t h e n a t u r e o f t h e p r d d u ~ t ; g a s o l i n e and r e s i d u a l s *

are t h e extremes. # eequence o f s t e p s i s be ing deviaed b

t o ' rapidly p rov ide compoei t ional in fo rmat ion on any o f

t h e s e p roduc t s wi th a minimum o f exper imenta l v a r i a t i o n s ;

i n t h i s manner, cornparisom o f p r o d u c t s can be meaningful ly

made,. oomporsi t i o n a l l y .

23 J e w e l l , e t a .gave t h e s t epwise p r e p a r a t i o n o f

t o t a l a romat ic concen t r a t e s . Var ious s t e p s nece s sa ry t o

maximise t h e e f f i c i e n c y o f t h e chromatographic cut-out

between s a t u r a t e s and a roma t i c s and t o p rov ide t o t a l

a roma t i c f r a c t i o n s , s u f f i c i e n t l y f h e of p o l a r non-

hydrocarbons, t h a t are s u i t a b l e f o r e x i s k i n g mass spec-

t r o m e t r i c methods of group-type a n a l y s i s were deecr ibed.

&leo , t h e Na t iona l Bureau o f S t a n d a r d s ha. r epo r t ed t h e

s u c c e s s f u l u se of s i l i c a - g e l i n an a d s o r p t i o n method f o r

3- removing a r o m a t i c s from petroleum s tock . T h i s analy- a

t ical p rocedure f o r s e p a r a t i n g a r o m a t i c s from s t r a i g h t -

run petroleum d i s t i l l a t e i s now i n e x t e n s i v e use ; a

~ i m i l a r ~ ~ - m e t h o d f o r s e p a r a t i n g o l e f i n i c g a s o l i n e h a s

a l s o been suggested. L ipk in , -- a t a lq40 had d e s c r i b e d a

method f o r s e p a r a t i n g a r o m a t i c s from s a t u r a t e s i n t h e

gas o i l and l u b r i c a t i n g o i l range. The major problem

f a c e d i n s e p a r a t i o n o f a r o m a t i c s i s ' t o comple te ly

s e p a r a t e mono- and d i a r o n a t i o corpounds from each o t h e r . 6

To ach ieve t h i s s e p a r a t i o n , one must be able t o moni to r

t h e c o n c e n t r a t i o n of each r i n g system as t h e s e p a r a t i o n

p r o c e e d s o r c a l c u l a t e t h e o v e r l a p of each system. I n

l i q u i d - e o l i d chromatography, wi th p u r e compounds and pure

s o l v e n t s on b a e i c alumina, one o b s e r v e s t h a t t h e re ten-

t i o n t i n e o f condensed d i a r o m a t i c s ( n a p h t h a l e n e s , e t c . )

ie r e l a t e d t o t h e amount o f r e s i d u a l m o i s t u r e on t h e

a d s o r b e n t ; r e t e n t i o n t imes approach a maximwn as p e r c e n t

water approaches zero. On ze ro p e r c e n t wa te r - alumina,

naph tha lene i s p r a c t i c a l l y adsorbed i r r e v e r s i b l y from

n-hexane s o l u t i o n .

m i l e t h e r e t e n t i o n t i m e s of monoaromatics a r e a l s o

r e l a t e d t o t h e m o i s t u r e c o n t e n t o f t h e adsorben t , they

a r e s i g n i f i c a n t l y s h o r t e r than t h o s e of t h e d i a r o m a t i c s . 56,57

A s demonst ra ted by Snyder and more r e c e n t l y by Pop l ,

e t al?'the a d s o r b a b i l i t y o f monoaromatics i s a1 so -- a f f e c t e d by t h e s t r u c t u r e of a l k y l s u b s t i t u t e s . P o p l ' s

s t u d i e s were made wi th 0.58 H20-A1 0 2 3'

T h i s i m p l i e s

t h a t maximum d i f f e r e n c e i n r e t e n t i o n t i m e s between mono-

and d i a r o m a t i c s can be r e a l i s e d on a ze ro p e r c e n t water-

alumina.

The purpose o f t h i s i n v e s t i g a t i o n i s t o s e p a r a t e , crude o i l bottom ( > 3 0 0 ~ ~ ) i n t o t h e p r i n c i p a l hydrocarbon

c l a s s e s ; s a t u r a t e s , a r o m a t i c s and r e s i n s f r a c t i o n s . The

a r o m a t i c s f r a c t i o n s were f u r t h e r s e p a r a t e d i n t o t h e i r

r i n g c l a s s e s , mono-, d i - , tri- and poly-aromatics . The

p h y s i c a l method which seems most r e a d i l y a d a p t a b l e t o

t h e problem i s chromatographic adsorp t ion .

The s e p a r a t i o n of a hydrocarbon m i x t u r e by se lec -

t i v e a d s o r p t i o n depends upon t h e f a c t t h a t t h e tendency

f o r hydrocarbons t o be adsorbed on s i l i c a - g e l d e c r e a s e s

i n t h e o rde r : a r o m a t i c s ) o l e f i n s ) s a t u r a t e s . When

a p p r o p r i a t e m i x t u r e o f t h e s e t y p e s of hydrocarbons a r e

passed i n t o a column o f g e l and e l u t e d w i t h a s u i t a b l e

p o l a r s o l v e n t , t h e f r a c t i o n s c o l l e c t ' e d appear i n t h e

f o l l o w i n g o r d e r : p u r e s a t u r a t e s , s a t u r a t e s - o l e f i n s .

mix tu re , p u r e o l e f i n , o l e f i n - a r o m a t i c m i x t u r e and p u r e

a romat ics .

2. I DISTILLATION OF THE CRUDE M P L E S - ,

The c r u d e s chosen f o r t h i s i n v e s t i g a t i o n were well-

These c r u d e s were d i s t i l l e d one a f t e r t h e o t h e r at 0

0 300 C f o r a p e r i o d o f about 6 h o u r s under a tmospher ic

p r e s s u r e . The reason f o r the, d i s t i l l a t i o n was t o concen-

t r a t e t h e components under i n v e s t i g a t i o n (a romat ics ) .

I t was observed t h a t as t h e tempera ture i n c r e a s e s , t h e

c o l ~ u r o f t h e d i s t i l l a t e s changed from c o l o u r l e s s ( a t

low tempera ture) t o ye l low and deep yel low a t h i g h e r tem-

p e r a t u r e s . T h i s cou ld be a t t r i b u t e d t o t h e f a c t t h a t as

t h e d i s t i l l a t i o h tempera ture i n c r e a s e s , t h e c o l o u r l e s s

l i g h t e r components of t h e c rude are s t r i p p e d o f f and t h e

co loured components become . more c o n c e n t r a t e d i n t h e

d i s t i l l a t i o n f l a e k . A t h i g h e r t empera tu res , Borne o f

t h e s e co loured components start t o d i s t i l o v e r a c c o r d i n g

t o t h e i r b o i l i n g p o i n t s ; o r i t cou ld be due t o cracking.

I t was p a r t i c u l a r l y n o t i c e d t h a t i n Yor la gi, t h e c rude

produced more d i s t i l l a t e s than r e s i d u e (bottom f r a c t i o n 0

> ~ O O ~ C ) . The t a b l e below shows t h e API of t h e c r u d e s

under i n v e s t i g a t i o n .

Table XII: 0

API o f Crudes Used -59

C RU DES O API

U g h e l l i E a s t 33.~1,~

U torogu

A crude of h igh O ~ ~ 1 . g r a v i t y should y i e l d more d i s t i l l a t e s

and less r e s i d u a l f u e l o i l than one of lower OAPI g r a v i t y .

T h i ~ was obse rved f o r Y o r l a gL crude o i l t h a t y i e l d e d more

d i s t i l l a t e s than t h e bottom f r a c t i o n ( > 3 0 0 ~ ~ ) . S i n c e

t h e r e i s no p r e c i s e c o r r e l a t i o n and t h e many anomal ies

60 t h a t o c c u r t h i s could p a r t l y be due t o t h e f a c t t h a t

c r u d e s vary c o n s i d e r a b l y i n r e l a t i v e p r o p o r t i o n s of

d i s t i l l a t e s ( g a s o l i n e - kerosene/gas o i l ) but a l s o because 0

t h e MPI g r a v i t y o f c r u d e s i s n o t o n l y dependent on t h e

b o i l i n g range d i a t r i b u t i o n o f i t s components (TBP curve)

b u t a l s o on t h e hydrocarbon composition. Thus a naph-

t h e n i c crude of a g iven OAPI g r a v i t y w i l l y i e l d more

d i s t i l l a t e s than a p a r a f f i n i c crude o f t h e same g r a v i t y ;

sp f o r a comparable y i e l d s t r u c t u r e , t h e p a r a f f i n i c crude

should have a h ighe r g r a v i t y .

2.2 SEPARATION ON U QUANTITATIVE BASIS

The c l a s s of compounds of i n t e r e s t , a roma t i c s , a f t e r ,

b e ing s epa ra t ed on s i l i c a - g e l column were concen t ra ted

through d i s t i l l a t i o n t o s t r i p o f f t h e so lven t and were

found t o c o n t a i n mix tu r e s o f compounds. These were

observed on Thin Layer Chromatography (TLC) p l a t e s on

which they were s epa ra t ed i n t o d i f f e r e n t bands u s i n g

s u i t a b l e s o l v e n t systems.

S e p a r a t i o n o f t h e a romat ic f r a c t i o n s i n t o t h e i r

r i n g c l a s s e s o f m o n e di- , tri- and po lyaromat ics were

c a r r i e d o u t on alumina column. The q u a n t i t a t i v e r e s u l t s

ob t a ined are shown on t a b l e X V I , X V I I and X V I I I a t t h e

appendix.

From t h e q u a n t i t a t i v e r e s u l t s and spec t ro scop i c

r e s u l t s obtained; ( s p e c t r a a t t h e appendix) it i s ev iden t

t h a t t h e r e a r e i n a d d i t i o n t o aromatic p ro tons o t h e r

p ro tons from s a t u r a t e d carbons. The in f ra - red s p e c t r a

from t h e t h r e e c rudes a1 so slmw c h a r a c t e r i s t i c s a t u r a t e d

hydrocarbon C-H s t r e t c h e s . if it i s assumed t h a t t h e

sa tu ra ted pro tons came from independent molecules

( i m p u r i t i e s ) r a t h e r than a l i p h a t i c o r sa tu ra ted group

a t tached t o t h e aromatic, then we can es t ima te t h e minimum I di - and t r i - a romat i c s us ing t h e n.m.r. i n t e g r a t i o n

according t o the fol lowing procedure ( e , g . t y p i c a l b

a l i p h a t i c C14H30 b.pt. 300'~).

moles of Al iphat ic carbons no. of a l i p h a t i c hydrogen 2

moles of aromatic carbons .y no. of aromatic hydrogen x 1.3

(where 1.3 i s t h e average consider ing CI4HI0 and CI0H8

1.2 f o r d ia romat ics and 1.4 f o r t r ia rorna t ics ) .

moles of aromatic carbons no. of aromatic hydrogen (1.3) moles of a l i p h a t i c carbons E no. of a l i p h a t i c hydrogen/:!

- - no, of aromatic hydrogen x (1.3) x ( 2 ) no, of a l i p h a t i c hydrogen

Using t h e above der ived equation, t h e maximum and minimum

range f o r d i - and t r i - a r ~ r n a ~ t i c s p r e s e n t i n t h e crude o i l

bottom was est imated as show i n Table XVIII i n t h e

The p e r c e n t ran,ge of t o t a l d i - t r i - a r o m a t i c s i n

t h e c rudes were 6.26 --+ 9 . 5 ; 1 2 . 8 _$ 21. j and 21.1

4 27.6 f o r Yor l a gL, Ughel l i -Eas t and Utorogu respec-

t i v e l y , ' .

2.3 SPECTROSCOPIC ANALYSIS OF THE AROMATIC SUB-TYPES:

dramatic n u c l e i c o n t a i n l a r g e c lo sed l o o p s of fl-

e l e c t r o n s i n which s t r o n g diamagnet ic c u r r e n t s a r e induced

by t h e magnetic f i e l d , Th i s e f f e c t r e s u l t s i n a para-

magpetic s h i e l d i n g at t h e a romat ic p ro tons , T h i s i s b

c a l l e d r i n g c u r r e n t e f f e c t . Benzene h a s one axis of

symmetry, . a l l t h e s i x p r o t o n s are i d e n t i c a l and g i v e s

one peak i n an nmr spectrum at 7 , 2 7 5 . Aromatic p ro tons

o f s u b s t i t u t e d benzene g e n e r a l l y absorb i n t h e range 8.0

- 6.5 E lec t ron- withdrawing group s h i f t e t h e absorp-

t i o n t o lower f i e l d a m d e l e c t r o n dona t i ng group s h i f t s

t h e a b s o r p t i o n t o h i g h e r f i e l d s because of t h e l o c a l

d iamagnet ic s h i e l d i n g e f f e c t .

' I n naph tha lene CIOH8, t h e r e a r e two a x e s of eymmetry

t h e s e a r e expected t o produce two s e t s o f s i g n a l s at

7.41 and 7.81Giepsctrum of pure naphthalene i n t h e I

appendix) . The I% -pro t o n s i n naph tha lene absorb a t lower

f i e l d than t h e g - p r o tons because t h e con t r ibu t ion of

t he two r i n g s a r e more important at t h e d - p o s i t i o n s i n c e

the l a t t e r i s c l o s e r t o both r ings . The o r d e r o f t h e

prot,on resonance i n anthracene can be explained i n the

same fashion. Here one f i n d s . 6 > Jd 7 ($, 2r

naphthalene an thracene

I n anthracene, C14HI0, t h e r e are t h r e e axes of

symmetry, t he re fo re , we expect t h r e e s e t s of p ro tons

which absorp a t 8.31, 7.91 and 7 .395 . Phenanthrene

which s t r u c t u r a l l y i s an isomer of anthracene with mole-

c u l a r formula C H h a s one a x i s of symmetry. F ive I 4 I0 s i g n a l s a r e expected which absorbs at 8.93, 7.88, 7.82,

8.12 and 7.71 6, the n.m.r. s p e c t r a l r e s u l t s of t h e

d ia romat ics i s o l a t e d i n t he work from t h e three crudes

under i n v e s t i g a t i o n , Ughell i-East , Utorogu and Yorla gL

show abso rp t ions of aromat ics p ro tons a t 7 .40Sand 7 . 8 4 s

i g n o r i n g t he peak at 7 - 6 5 i n a d d i t i o n to a l i p h a t i c

p ro ton a b s o r p t i o n peaks a t I .I due t o CH -; f o r Ughe l l i

Ea s t ; which could be remini s c e n t o f naph tha l en i c abeorp-

t i ona . For t h e i n f r a - r ed s p e c t r a o f t h e Ughel l i -Eas t

bottom ( ') 300°c), t a b l e X I X (append ix) , t he a romat ic

peaks a r e b e s t p icked o u t by checking on three r e g i o n s

of absorp t ion . Thus t h e C-HtS a romat ic s t r e t c h abso rbs

n e a r 3 ~ 3 ~ c n - 1 . wi th t he p resence o f r i n g s t r e t c h i n g I

no& C ~ C observed n e a r 1585crn-', 1440cm-I and 1365cm-', , t h e doubt of whether i t i s a lkene C-H i s removed. There

i s a l s o t h e out-of-plane bending C-H modes absorb ing a t

775cm-I which i n d i c a t e t h e s u b s t i t u t i o n p a t t e r n on t h e

benzene r ing . I t i s ev iden t t h a t from o t h e r bands, t h e r e - i s an amount o f a roma t i c u n s a t u r a t i o n from t h e i s o l a t e d

d i a r o m a t i c s from Ughel l i -Eas t bottom f r a c t i o n ( > 300 '~)

The i s o l a t e d d i -aromat ics o f Ughel l i -Eas t h a s ab-

s o r p t i o n s at 245, 270, 282, and 290 nm i n t h e uv reg ion ,

The i r s p e c t r a of d i a r o m a t i c s from U torogu bottom

. - ( ) 3 0 0 ~ ~ ) f r a c t i o n , Table XX (appendix) show a romat ic

a b s o r p t i o n at 3 0 4 0 ~ ~ ' and f o u r o t h e r peaks at 1440,

1595, I690 and I890 an- ' . There a r e ove r tones o r CZC

s k e l e t a l v ibra t ions . The other peaks due t o out-of-plane

bending of t h e C-H bonds m e observed a t 945, 870, 805,

780, 745 cm-l.

I n t h e nnr, Table X X V (appendix), t h e s i gna l s a r c a t

7.5 and 7 . 8 s . I t i s d i f f i c u l t t o absign t he o ther peak

a t 7.15 &. I t i s i n t e r e s t i n g a l so t o no t i ce t h e o the r

CHg-Ar attached t o t h e benzene r i ng absorbing a t 1.2 % and CH2-Ar a t 2.55 '6. In this crude, t h e r e i s a s t rong

absorption of aromatics r e l a t i v e t o a l i p h a t i c s i n t h e I r

spectrum a s this c o r r e l a t e s w i t h t h e information from

t h e n.m.r. spectrum. b

The uv-spectral r e s u l t of t h e Utorogu, t h e di-

aromatic absorption a t 250, 274, and 295 nm i s

i nd i ca t i ve of naphthalene. There i s no absorption above

300 nm i n t h e w region showing absence of anthracene.

The spec t ra of Yorla gL i s s imi l a r t o t h a t of t h e

~ ~ h e l l i - & s t and Utorogu. The uv ana ly s i s shows highest

absorption arould 225 nm, 245 nm, 270 nm, 200 nm and 290 nm,

This i nd i ca t e s t h e presence Of naphthalene. The n.m,r. shows

which a b s o r p t i o n a t 7.35 & and 7.75 6. Other peaks,could e i t h e r

be due t o CH - A r and CH - A r appear at 1.25 $'and '

3 2 2.4 6 r e s p e c t i v e l y o r independent p r o t o n s a t t a c h e d t o

a l i p h a t i c groups.

The i s o l a t e d t r i a r o m a t i c s from Utorogu show absorp-

t i o n on t h e i r s p e c t r a at 30)0cd1 which i s c h a r a c t e r i s -

t i c of C-H a romat ic s t r e t c h . There i s a l s o a r e l a t i v e

p ropo r t i on of a l i p h a t i c hydrocarbons p r e s e n t as i n d i c a t e d

at 2710 - 2910cm-I due t o C - ~ ' s a t u r a t s d s t r e t c h which c y

arise from a l k y l s u b s t i t u e n t a on a romat ic r i ngs . Other

peaks t h a t suppor t t h e p resence o f a roma t i c s are observed

a t 1880, 1690, 1590. I 440 and 1365crn-I. These show

a roma t i c s u b s t i t u t i o n p a t t e r n . There a r e a l s o peaks at

865, 800, 780 and 740ck-I showing out-of-plane v i b r a t i o n

of a romat ic r ings . . ,Anthracene u s u a l l y absorb$ i n t h e

uv r eg ion a t 253, 375 wh i l e phenanthrene abso rbs a t 252,

293, 330. The i m l a t e d t r i a r o m a t i c s f rom Utorogu show ,

more an th racene than phenanthrene. The peaks are ebsgrved

wi th maximum abso rp t i on arounh 330 - 380nm.

The n.m.r. of t h e Utorogu show absorption peaks a t

7 . 4 6 , 8.Id and 8 . 4 5 5 . Other peaks at I.OJ and I . 3 &

could be due t o CHq-Ar.

I The t r i a r o h a t i c s n.m.r. spect ra of both Utorogu and

Yorla gL a r e s imi la r and they show a s i n g l e t a t t h e H

pos i t i on w i t h absorption a t 8.45 g. These crudes show

c h a r a c t e r i s t i c f e a t u r e s of a t yp i ca l anthracene.

The i solated t r i a romat ic s of Ughelli- East crude

show s imi la r f e a t u r e s i n t h e i r and n.m,r. spec t ra a s t h e

o the r crude. Deta i l s of analyses a r e given a t appendix.

2.4 CONCLUSON

From the above analyses, we have beer! ab l e t o i s o l a t e b

di- and t r i -aromat ics from the bottom f r a c t i o n ( > 3 0 0 ~ ~ )

of t h r e e Niaerian well-head crudes using chrornato~raphic

methods, The r e s u l t s obtairied showed a percent range of

6.26 -> 9.5; 12.8 - j 21.3; 27.7 --+ 27.6 f o r Yorla

gL9 Ughelli-East and Utorogu respect ive ly f o r t h e sue

t o t a l of di- + t r i -aromat ics i n t h e t o t a l crudes.

However, t h e quan t i t a t i ve r e s u l t obtained above using

n.m.r. spect ra da ta of t h e i s o l a t e d d i - and tri-

aromatics Prom the bottom f r a c t i o n (> 300'~) i s only an

est imate and f u r t h e r de t a i l ed i nves t i ga t i ons could be

necessary i n this area. The following aspec t s a r e

suggested f o r f u r t h e r studies.

( 7 ) Standard mixtures containing known amounts of

r epresen ta t ive subaromat ics : though resonances due t o

a l k y l groups a t tached t o t h e aromatic r i n g s and methylene

and methine p ro tons of t h e non-aromatic c o n s t i t u e n t s may

s t i l l p resen t a problem.

( 2 ) Gas chromatographic work on t h e bottom d i s t i l l a t e s

( using s tandards and equipment with e l e c t r o n i c in te l r r a to r s )

may provide u s e f d r e s u l t s ; though it i s d i f f i c u l t t o g e t

s t a t i o n a r y phases t h a t may remain s t a b l e a t such

temperature ( > 3 0 0 ~ ~ ) .

( 3 ) Mass spec t ra of t h e bottom d i s t i l l a t e a t low

(ambient) ion i s ing v o l t a g e may be explored,

Nevertheless , it i s i n t e r e s t i n g t o n o t e t h a t t h e n,m,r,

spec t ra d a t a has given an es t imate propor t ion of t h e s u b

aromatic p resen t i n t h e crudes under i n v e s t i g a t i o n which

c o r r e l a t e s with t h e information from OAPI, i n f ra - red

s p e c t r a and u l t r a - v i o l e t spectra .

CHAPTER THREE

3- 0 EXPERIMENTAL

3. I DISTILLATION OF THE CRUDES

Crude o i l s used f o r these ana lyses were Ughelli- L

East, Utorogu and Yorla Light 9 . Figure V shows the

sepa ra t ion p a t t e r n used f o r t he p m j ec t .

About 400mls ( 395.4g) Ughelli-East crude o i l was

pu t i n a two- l i t re double-qecked round bottom f l a s k . b

To one of t he necks of the f l a s k was connected a Vigreux

f r a c t i o n a t i n g column coated with a s i l v e r y m a t e r i a l to

minimise hea t l o s s with a condenser. A quick- f i t

thermometer having 0 - 3 6 0 ~ ~ range was f i x e d at the top I

I

of t h e f r a c t i o n a t i n g column, The condenser was connected

to s Perkin r ece ive r adapter , The o t h e r neck was

stoppered, The f l a s k with the whole set-up was lagged

with f i r e b lanke t and heated i n a h e a t i n g mantle u n t i l

t he o i l began to re f lux , D i s t i l l a t e s were c o l l e c t e d

wi th in 40% i n t e r v a l s l n t he r e c e i v e r , Table XI11 shows

t h e data obtained.

The o t h e r two crudes, Utorogu and Yorla gL were

d i s t i l l e d under t h e same atmospheric condi t ions , Tables

XIV and XV show t h s data obtained respec t ive ly .

0 !£he weights of f r a c t i o n s b o i l i n g above 300 @ were

157.22g, 212.4% and 69.17g f o r Ughel l i -East , Utorogu 1 and Yorla 9 r e s p e c t i v e l y .

3.2 - De-asphalting of the Residua (73 WOC)

3.64g of t h e Ughell i-East bottom f r a c t i o n ( ~ 0 0 ~ ~ )

were mixed with n-hexane (200ml) shaken and r e f r i g e r a t e d

( 3 3 mins) t o p r e c i p i t a t e t h e asphaltenjes. The hexane-

so luble f r a c t i o n was recovered by f i l t k a t i o n followed by

d i s t i l l i n g o f f the hexane s o l v e n t . The m a l t e n e ( ~ 12 +

s o l u b l e o rqen ic matter) w a s kept f o r fu r the r a n a L y s i s . The same process was reprated f o r r e s i d u e o f ~ t o ~ o g u and

L y o r l a 9 . The w e i g h t : of dsphal tene recovered are ,

recorded on t a b l e XVI.

5.2. I Determinat ion of Benzene I n s o l p b l e F r a c t i o a About 3 . 5 ~ o f the meltene from Ugbelli-East wds

added t o 70ml of benzene and r e f l u x e d :or 2 hours . The

benxene i n s o l u b l e s were s e p a r a t e d by f f l t r a t i o n and d r i e d

in a d e s s i c a t o r . The f i l t r a t e was f u r t h e r concent ra ted

by d i s t i l l a t i o n a t low h e a t t o about 3 - 5 m l . me same

' procedure was r epea ted f o r Utorogu and Yorla 9 L .

The weight of benzene i n s o l u b l e

Crude O i l D

n-hexane preLiPi ta t ion J

I

8 I I D i s t i l l a t i o n

I +

Liquid chromatography on alumina/si l i ca-gel

I

Light di s t i ' l l a t e . -

<

Saturated HC

Fraction bo i l ing 'above 300°C

I

Resins

I

~ i q u i d chromatography on alumina column

T I I

f mono-aromatic

F ig V: Separation Pattern f o r the Project

f r a c t i o n f o r t h e t h r e e c r u d e s under i n v e s t i g a t i o n a r e

p r e s e n t e d on t a b l e XV.

3 3 S e p a r a t i o n of t h e Bottoms ( >300°c)

3.0g of t h e mal tene from Ughel l i -Eas t was a p p l i e d

on t o a I60.50g s i l i c a - g e l MN-Kiesegel (60,o. 2 - 0.5mm/

35 - 70 mesh) column. The s i l i c a - g e l was a c t i v a t e d at

I 2 0 C and a l lowed t o coo l i n a d e s s i c a t o r b e f o r e use ,

The column was packed by W i n g a s l u r r y of s i l i c a - g e l b

w i t h n-pentane and i n t r o d u c e d i n t o a d r i e d and c leaned

The l i q u i d was a l lowed t o f low o u t a t such a rate t h a t

i t n e v e r f e l l below t h e l e v e l of t h e adsorben t . When

a l l t h e a d s o r b e n t ws added, t h e s o l v e n t was a l lowed t o

d r a i n s lowly u n t j l no f u r t h e r s e t t l i n g o f t h e column I

took p l a c e , bu t t h e l e v e l o f t h e s o l v e n t was n e v e r

al lowed t o f a l l below t h e top of t h e column. The column

was f i l l e d t o two- th i rds of t h e l e n g t h o f t h e column,

a n o t h e r glass wool was p laced at t h e top o f t h e column.

-

column o f l e n g t h 70cm and i n t e r n a l d iamete r o f about

I.5cm, wi th a glass wool p laced a t t h e bottom, The

s l u r r y was added g r a d u a l l y wi th g e n t l y t a p p i n g o f ' t h e

column wi th a rubber bung, whi le t h e t a p i s k e p t opened.

8 5

The s e p a r a t i o n of t h e deasphal t e d e x t r a c t began wi th

n-pentane, t h a t e l u t e d t h e s a t u r a t e s , about 200ml of n-

pen tane was used. The a romat ic hydrocarbons were e l u t e d

wi th about 250ml o f benzene and methanol e l u t e d t h e r e s i n s

( e s s e n t i a l l y N , SI 0 compounds). The same p r o c e s s was I

repea ted f o r 3g each o f t h e Utorogu and Yor la l i g h t 9 L

deaspha l t ed e x t r a c t . The volume of t h e a r o r a t i c e x t r a c t

wae concen t r a t ed by d i s t i l l a t i o n at low h e a t and kep t f o r

f u r t h e r chromatography on alumina. *

3.3.1 Sepa ra t i on of ZArornatics i n t o Ring C l a s s e s

&bout 0.5g ' a l i q u o t 8 o f t h e t o t a l a romat ic

f r a c t i o n from Ughell i -East bo t tolr~s, s t r i p p e d o f t h e

benzene through d i s t i l l a t i o n , , was s epa ra t ed i n t o r i n g

c l a s s e s on I80.80g of alumina column. 'Ihe alumina was

. a c t i v a t e d a t 4 0 0 ' ~ f o r I 2 h r s i n a fu rnace and cooled i n

a d e s s i c a t o r be fo r e use. The column was packed as

I d e s c r i bed f o r s i l i c a - g e l column i n s e c t i o n 3.3. The

monoaromatics were e l u t e d with 5% benzene i n 95% n-

pen tane and t h e d i -aromat ics with 15% benzene i n 85%

n-pentane whi le t h o polyaromat ica were e l u t e d with 20%

benzene, a$ d i e t h y l e t h e r and 6% methanol.

The p u r i t y of t he f r a c t i o n s w a s ' t e s t e d by t h i n

l a y e r chronatography.

The same p roces s was repea ted f o r Utorogu and Yorla

L' l i g h t 9 aromatic e x t r a c t s .

3.3.2 Thin Layer Chromatography (T.L.C.) o f t h e Aromatics ,

Obtained

T.L. C. p l a t e s were prepared us ing B. D.H. s i l i c a - g e l

C6. 3Og of s i l i c a - g e l G6 were a g i t a t e d toge the r to homo- b

gehize the s l u r r y formed i n 60ml o f d i s t i l l e d water,

5 x 20cm T.L.C. p l a t e s were coated to 0.5mm th ickness ,

a i r -d r i ed f o r 30 min - I h r and a c t i v a t e d i n an oven a t

110 C f o r ' 1 h r p r i o r to use. The d i f f e r e n t e l u a t e s o f mono-

aromat ics , d i a r o a a t i c s , polyaromat ics from Ughell i-East

crude were red isso lved i n pentane and spo t t ed s i d e by s i d e

on the prepared T.L.C. p l a t e s with t h e i r f r a c t i o n ) 3 0 0 ~ ~ .

Three types of so lven t systems were used. They were 95%

n-pentane with 5% benzene f o r the mono-aromatics, 15%

benzene i n 8596 n-pentane f o r the diaromat igs , 20$ benzene,

20$ d i e t h y l e t h e r and 60$ methanol f o r t h e polyaromatics,

The sepa ra t ion was poor on t h e T.L.C. p l a t e s , t he re fo re ,

another ~ o l v e n t $yetem was sought. This was obtained

from l i t e r a t u r e . 6' The separat ion of t h e f r a c t i o n

300 '~ on alumina column was repeated usin8 t h e

following solvent systems; n-pentane alone f o r mono-

aromatics; O,@ e thy l e t he r i n 99,% n-pentane f o r

dl-aromatics; 8% e thy l e t he r . i n 9296 n-pentane f o r tri-

aromatics and 5046 e thy l e t he r i n 50% n-pentane f o r t h e

polyaromatics, The d i f f e r e n t e l u a t e s were col lec ted .

There were d i s t i n c t separa t ion bands a t t h e add i t ion

of each solvent system; t h e eluate f o r the wono- b

aromatics were colour less , w h i l e t h a t c o l l t c t e d f o r

dl-aromatics were yellow; f o r t h e t r i -a romat ics , t h e

i n t e n s i t y of t h e yellow coloura t ion increased; t h e

e l u a t e of t h e polyaromatics was dark brown i n colour.

Only t h e midstream e l u a t e were used f o r spec t r a l

analys is , A t each s t age of t h e e lu t ion , excess so lvent

was used t o ensure complete ex t rac t ion of t h e des i red

aromatics,

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APPEND1 X I

1 I TABLES

Table XCII D i s t i l l a t e from Ughelli-East Crude

0 C rud e Temperature C Volume/ml Colour of d i s t i l l a t e

Ughelli-East 40 - 80 2. 5 Colourless

400m1( 354.4g) 80 -I 20 I5*4 _ Colourless

I20 -160 25.4 Colourless

I60 -200. 27*8 Colourlesa , 200 -240 35.0 Light Yellow

240 -280 50.0 Yellow

280 -300 46.0 Deep Yellow

Table XIV: D i s t i l l a t e from Utorogu Crude

Crude Temperature C Volume/ml Colour of d i s t i l l a t e -

Utorogu 4001111 40 - I00 2.2 Colourless

( 368- 8g) I00 - 200 17.5 Colourless

200 - 240 32.4 Very l i g h t yellow

240 - 280 50.0 Yellow

280 - 300 33.0 Yellow

Table XV: D i s t i l l a t e from Yorla gL Crude

0 Crude Temperature C Volume/ml Colour of d i s t i l l a t e

orl lo gL 40 - I20 57 Colourleas

400m1( 328g) I20 - I80 109 Colourless

I80 - 240 74 Colourless

240 - 300 60 Very very l i g h t yellow

Table XVI: Q u a n t i t a t i v e Result

---

Crude W t . of W t , o f , W t of W t . of W t . o f , bo t tono aaphal benzene n-hep tane benzene m e than01 ( ) 300 tenes i n so lub le e lu4 te e l u a t e e l u a t e c ) ( 3l3 ('3) (6 ) ( 43) ( g ) ( g )

East

Yorla 0.0050 0.0001 2.39 0.57 0.02

Table X V I I : Quant i ta t ive Result Obtained f o r the Aromatic Sub-types Crudes Frac t ion ( ) 308~) ( ~ r o m a t i c s

, I

U to rogu Yo rla Ughelli-East - W t . of aromatic s t a r t e d wi th(g) 0.5 0.5 0.5 W t . of mono-aromatics obtained ( 8 ) 0. 17 0.19 0.16 W t . of diaromatics obtained(g) 0.10 0.15 0.11 W t . of t r i a romat i c s obta ined(g) 0.14 0.15 0.13 U t of polyaromatics obta ined(g) 0.09 0.01 0.09

Table X V I I I : D i s t r i b u t i o n of Aromatic Sub-types i n Some Niger ian Crude O i l s

Ughel l i -Eas t u torn@ Yor la 9' W t . of 400ml of crude ( g ) 354.4 368.8 3 28 W t . o f bottom f r a c t i o n ( ) 3 0 0 ~ ~ ) g 157.2 21 2.4 69.17 W t . $ of btbttom f r a c t i o n ( * 3 0 0 ~ ~ ) 44.4 57.6 21.1

6 o f d i a roma t i c s i n bottom f r a c t i o n ( > 300°C) 22 20 30

$ o f d i a roma t i c s i n c rude 9.8 11.5 6.3 $ of t r i a r o m a t i c s i n bottom f r a c t i o n ( > 300%) 26 28 I 5

16.1 $ o f t r i a r o m a t i c s i n c rude 11.5 p. 2

E s t . max.$ of d i a roma t i c s from n.m. r spectrum I1 15.7 21

Es t . mad of t r i a r o m a t i c s from n.m. r. spectrum I8 21 12.4

Est . mink d i a roma t i c s i n c rude 4.9 9.0 4.4

Eat min$ o f t r i a r o m a t i c s i n crude 7.9 12.1 1.86

$ of d i + t r i a roma t i c s i n crude b i n $1 12.8 21.1 6.26 $ o f d i 4 t r i a roma t i c s i n crude (max 4 & ) 21.3 27.6 9.5

Table X I X : I n f r a r e d Spectrum a f ~ i a r o n a t i c s from Ughel l i - ,

East Bottom F r a c t i o n ( > 300°C)

- Absorpt ion frequency Wavenumber Remark s

cm-I/ intensi t y jum 3030( W ) , 3.30 k romat ic C-H s t r e t c h i n g 2907 ( w) 3.44 a l k y l C-H s t r e t c h i n g 2830( b b ) /- 3 -53 a l k y l C-H s t r e t c h i n g 1585s w 6.31 C &C s k e l e t a l in-plane

v i b r a t i o n due t o a roma t i c s I440 s -"bog4 n

96.

Table X I X Contd, -- - - --

hbsorp t i o n frequency Wavenumber Remarks

cn-'/intend t y ;/M

13658 , - 7.33 C ZC s k e l e t a l in-plane v i b r a t i o n due to aromat ics

800 s &I 2.50 C-H ou t-of-plane bending nodes

7758 -12.90 I n d i c a t i n g s u b s t i t u t i o n

Table XX: I n f r a r e d Spectrum of Diaromatics from Dtorogu . bottom f r a c t i o n ( 3 3 0 0 ~ ~ )

I

Abaorp t i o n frequency Wavenumber Remark s

cmD1/in t en si t y ~ u m

-3, 29 aromatic C-H s t r e t c h i n g - 3-43 a l k y l C-H s t r e t c h i n g

1890(w,b) "5 5- 29 Overtone o r combination bands

169P(w) . . ~ 5 . 9 2 C - -C s k e l e t a l in-plane vib, due to aromat ics

159% 8) 6.27 w

I440( B) 6-95 m

~ 1 0 . 5 8 Out-of-plane .bmding of the C-H bonds . .

Table XXI: Inf ra - red Spectrum of Di-aromatics form Y o r l a Bottom f r a c t i o n ( Y 300~4)

Absorption frequency Wavenumber Remarks

cm- I /~n tens i ty jum

3040 - 3020(w,b) 3.29-3.31 Aromatic C-H s t r e t c h i n g

2920 - 2860(s) 3.42-3.50 a l k y l C-H s t r e t c h i n g

-6.25 C - d p * C s k e l e t a l in-plane vib. due t o aromat ics

+ 6.90 rn

-7.25 e

tv 9.62 Out-of-plane C-H bending modes i n d i c a t i n g subs t i tu t ion ,

+ 10.47 rn v

~ 1 1 . 9 7 rn

Table X X I I : Inf ra - red Spectrum of t r i a r o m a t i c s from Ughelli- Eaet Bottom Frac t ion (7 300QC)

Absorption frequency Wavenumber Remarks

cmol / ~ n t en a i t ~ u m '

3030( w) ~ 3 . 3 0 Aromatic C-H s t r e t c h i n g

2900 ( w) / ~ 3 * 4 5 a l k y l C-H s t r e t c h i n g

~ 3 . 5 3 rn

w5.95 . C z C s k e l e t a l in-plane vib. of a romat ics

A* 31 rn

IO20( w, b) ~ 9 . 8 Out-of-plane C-H bending modes 775(s ) '"12.9 II)

Table XXIII : I n f ra-red ' ~ ~ e c t r u m o f Tr i -aromat ic Utorogu Bottom F r a c t i o n ( 3 300°C)

Absorpt ion frequency Wavenumber Remark e

cm-' / I n t e n s i t y I.up

3030( w) 3-30 Aromatic C-H s t r e t c h i n g

2910( 8) -3-44 a l k y l C-H s t r e t c h i n g 2840 ( W) r 3- 52 *I

Aromatic s u b s t i t u t i o n C* a *C S k e l e t a l in-plane vib. o f aromatics

m b

Ou t-of-plane C-H bending modes m

Table XXIV: NMR Spectrum o f Diaromatic Ughell i-East Bottom F r a c t i o n ('7 300°C)

&VALUE 7-va lue Remark s

I. I 8.9 CHI-at tached t o a romat ic 1.4 8,6 acyclic-me thy lene group 7.40 2.6 Aromatic pro t o n s 7.60 2.4 /Aromatic pro t o n s 7.84 2.16 4romat ic pro t o n s

Table X X V : NMR Spectrum of Diaromatic from Utorogu Bottom Frac t ion ( )300rr

6-value 7,-value Remarks

1.0 9 - 0 CH3-attached to aromat ic r i n g

8.0 a c y c l i c methylene group 7.45 CH a t t ached t o aromatic nucleus

3 2.85 Aromatic pro tons

7.5 2.5 Aromatic p ro tons

7.8 2.2 Aromatic pro tons

Table XXVI : NNR Spectrum of ~ r i a r o m a t i c from Ughelli-East Bottom Frac t ion ( >go=)

8

6-value t - v a l u e Remark s

0.9 9.0 CH a t t ached to aromatic r i n g

1.2 3-

8.8 -CH a c y c l i c methylene group 2- 7.35 2.65 Aromatic p ro tons

7 85 2,15 . Aromatic pro tons

8.4 I. 6 Aromatic pro tons

Table XXVII: F R Spectrum of Tr iaromat ic -- from Utorogu - Bottom Frac t ion (> 3 0 ~ ~ ) -

- -- -.

6- VALUE 7; -value Remarks

1.0 9.0 CH group a t t ached t o aromatic r i n g 3 1 3 8.7 -CH3-group

7.4 2.6 4rornat i .c p ro tons

8. I 1.5 Aromatic pro tons

8.45 I. 55 Aromatic pro tons

Table XXIX: .n.m.r. Spectrum of Di-aromakics from Y o r l a Bottom F r a c t i o n ( ) 300"~)

Ctva3ue T, -va lue Remark s

I. 25 8.75 CH3 group a t t a c h e d t o a r o m a t i c r i n g

7 - 3 5 2.65 Aromatic p r o t o n s

7.75 2.25 Aromatic p r o t o n s

Table XXX: n.m.r. Spectrum o f t r i - a r o m a t i c s from Yor la BOf t6lP F r a c t i o n (,? 3 0 0 0 ~ ) b

6 -value -value Remark s

-CH3- 9.1 group a t t a c h e d t o a romat ic '

r i n g

8. 7 -CHI group

2.6 Aromatic p r o t o n s

2. I Aromatic p r o t o n s

1-65 Aromatic pro t o n s

! l! I I.',

i: i:

! t

I I I

A W S D I X 3

Q u a n t i t a t i v s ~ , s t i m a t i o n o f the ~romatic Types

moles of a l i p h a t i c car9on no. of a l i p h n t l c hydrogen

04 of d i a r o n a t i c s from n.ru.r. spectrum

Estimation max.% of d iaromat ics f r s n n.m,r.

0.71 x 3W, (3CW is 46 ~f diarom- - 21% atics i n the frsctionj

. x s t . aHx. o f d i a r 2 n ~ : t i c o of Yor1.a 9L in tb-e bottom

PI 4.75 x 70w - 82.7%) (aromatic i n T75 bottom f r ac t ion )

. Est . mox.% t r i - ,wom+t ics from Yt3rl.a $IL becomes

ao le of srom:ttic carbon =

mo las o f aliphatic ca r ton no. o f srornatiu hydrogen (1.2)(?) no. cf s l i p h s t i c hykrogen

T r i ~ r o n a t i c s from TTtorogu Crude ..-

N = no. of a r o n n t f c hydrogen (1.232 no. of ~Zip,f iqt ic hydrogen

E s t ma*:! of disromsticn f rom n.m.s. s p e c t r u ~ from fraction

P 6.7C) :1 2% 6~ -1GTA

?st. mi??, $/ of. t r i y r o m a t i c s in the crude he

0.15 x 44.494 - 7.9%

. Absorbance Transmittance 0-1 A Range

I %s!-d t a n slow 0 A~SU&KU Range 0-0.2A D O - 1 QA

mm cb-tm 'Date

.. AtcorOane - . Transmittance 0-1A ibngo

. . 8 L ' I I . , , 1 , , 1 I , I , . , , I , , i , : : ,

I Concentration

Reference

Path Length I Scan speed -El -0 + m b a n w Range MZAUO-1-OA 0

mm Operata Date

Absorbance \ Transmittance O

I C o n m t m n

Ref-

Path Length

- 'Absorbance Transmittance 0-1A Range

I and Formula iJtm,& dG44 r Scan Spesd f a n z& a Ref- Absorbs- Range 0-0.U 0 0 - r n 0 -krce rnm Opentor Dar