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Aspects on reaction intensification
Åbo Akademi, Faculty of TechnologyDepartment of Chemical Engineering
Process Chemistry Centre,Laboratory of Industrial Chemistry
and Reaction EngineeringFI-20500 Turku / Åbo Finland
Tapio Salmi
Process intensification
Structures and methods which lead to a considerable compression of the equipment size, and to a more efficient, selective and clean production
Raw material ProductsProcess
Process intensification
Intensification methods
Ultrasonic techniquesMicrowave techniquesIntegrated reaction and separationReactions under extreme conditionsUnsteady state operationEnhancement of mass and heat transfer...
Process intensification
Intensification equipment
Structured reactors (monoliths, foams, fibre structures, columns)Reactors with internal heat exchangersMicroreactorsEquipment for reactive separation Spinning disk reactors...
Reaction intensification
Intensification of the chemical reactor performance is a vital part of chemical reaction
engineering and process intensification
Reactant molecules Product moleculesChemical reactor
Batch and continuous reactors
Three-phase reactors in laboratory scale
New catalyst materials have emerged
monoliths fibres/cloths foams
Benefit: low pressure drop, suppressed diffusion resistance inside the catalyst particle
Challenge: activity, selectivity, metal particle size, chemical state
Monolith catalysts
Continuous reactor –KATAPACK column
Fibre catalystsFibre catalysts
4 nm
TEM image of the 5 wt.% Pt/Al2O3 (Strem Chemicals) catalyst
SEM image of the 5 wt.% Pt/SiO2 fiber catalyst
1 mm
125-90 m particles
D = 27% dPt= 4 nm
D = 40% dPt= 2.5 nm
Catalysts in micro and nanoscale
5 m
TEM imageSEM image
4 nm5 m
• 5wt.% Pt/SF (Silica fibre) 5wt.% Pt/Al2O3 (Strem)
4 nm
Reaction and mass transfer in three-phase reactors - bottlenecks
Bulk Film Bulk Film Solid
Reaction and diffusion
Even though the governing phenomena of coupled reaction and mass transfer in porous media are principally known since the days of Thiele and Frank-Kamenetskii
Reaction and diffusion
They are still not frequently used in the modeling of complex organic systems, involving sequences of parallel and consecutive reactions.
Evaluation of Thiele modulus and Biot number for first-order reactions are not sufficient for such a network comprising slow and rapid steps with non-linear reaction kinetics.
ei
GiM D
RkBi
Biot
eD
kR
'
Porous particle
dr
rNdrr
dt
dc SiS
pipi 1
j
jjiji aRr
Reaction, diffusion and catalyst deactivation in porous particles
Particle model
Rates
Separable and reversible deactivation kinetics
tkjjjj
jeaaaa *0
*
1,1 1
1'1*
0*
ntnkaaaa n
j
n
jjj
Fresh catalyst sample Recycled catalyst sample
Raney-NickelCatalyst
Porous particle model
dr
dcDN i
eii
dr
dc
r
s
dr
cdDaR
dt
dc iieijjijpp
i2
21
, where Dei=(p/p)Dmi
0dr
dci 0r
Rcckdt
dcD iiLi
Rr
iei
Rr
Boundary conditions
Batch reactor
GLGLipii aNaN
dt
dc
RcckN iiLii
GiLi
i
bLii
bGi
GLi
kk
KcKc
N1
Liquid phase mass balance
Liquid-solid flux
Gas-liquid flux
Example systems
Hydrogenation of
Citral
LactoseO O
OH
OH
OH
OHHO
OHOH
OHOH
Lactose Lactitol
O O OHOH
OH
OHHO
OHOH
OHOH
LactulitolLactulose
OOH
OH
HOOH
OH
Galactose
+Glucose
OHOH
OH
HOOH
OH
Galactitol
OH
OH
OH
OHOH
HO
Sorbitol
H2
H2
H2
H2
H2
IsomerizationOHˉ
Hydrolysis
O
O
O
OHHO
OH
OHHO
HO
HO OH
O
O
O
OH
OH
OH
OHHO
OHOH
OH
Lactobionic acid(Na-salt)
DehydrogenationHydrogenation
O
OH
OHHO
OH
OH
O
OH
O OHOH
OH
OHHO
OHOH
OH
O
O O
OH
OH
OH
OHHO
OHOH
OHOH
O O
OH
OH
OH
OHHO
OHOH
OHOH
Lactose Lactitol
O O OHOH
OH
OHHO
OHOH
OHOH
O O OHOH
OH
OHHO
OHOH
OHOH
LactulitolLactulose
OOH
OH
HOOH
OH
Galactose
+Glucose
OHOH
OH
HOOH
OHOH
OH
OH
HOOH
OH
Galactitol
OH
OH
OH
OHOH
HOOH
OH
OH
OHOH
HO
Sorbitol
H2
H2
H2
H2
H2
IsomerizationOHˉ
Hydrolysis
O
O
O
OHHO
OH
OHHO
HO
HO OH
O
O
O
OHHO
OH
OHHO
HO
HO OH
O
O
O
OH
OH
OH
OHHO
OHOH
OH
O
O
O
OH
OH
OH
OHHO
OHOH
OH
Lactobionic acid(Na-salt)
DehydrogenationHydrogenation
O
OH
OHHO
OH
OHO
OH
OHHO
OH
OH
O
OH
O OHOH
OH
OHHO
OHOH
OH
O
Modelling resultsCitral hydrogenation
0 50 100 150 200 250 300 0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
time (min)
Re
lativ
e co
nce
ntr
atio
n
citronellal
citral
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0
0.05
0.1
0.15
0.2
0.25
Hydrogen
Citral
Citronellal
c m
ol/l
x
trilobic catalyst particle
0 50 100 150 0
0.2
0.4
0.6
0.8
1
x
Intrinsic kinetics,thin catalyst layers
concentration profiles inside a trilobic catalyst particle
Lactose hydrogenation to lactitolIntrinsic kinetics
0 50 100 150 200 250 3000
5
10
15
20
25
30
35
40
45
time (min)
w-%
20 bar
20 bar
70 bar
70 bar
T=110C, P=70 bar
Lactose
Lactitol
Lactose hydrogenation - diffusion
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10
0.2
0.4
0.6
0.8
1
1.2
1.4
x
c (
mo
l/l)
0.03 mm
0.3 mm
0.3 mm
0.03 mm1.0 mm
1.0 mm
3.0 mm
3.0 mm
Concentration profilesinside catalyst particlewith different particle sizes
SurfaceCenter
LactoseLactitol
0200
400600
0
0.5
1
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0200
400600
0.5
1
0
0.2
0.4
0.6
0.8
1
1.2
1.4
Concentration profiles of lactose inside a catalyst particle
No deactivation Deactivation
surface
surface
center center
timetimex
x
4FeSO4 + O2 + 2HSO-4 + 2H3O- ®
2Fe2(SO4)3 + 4H2O
Proceeds as a gas-liquid reaction but catalyst helpsCatalyst: Active carbon
Oxidation of ferrous sulphate to ferric sulphate
Simultaneous catalytic and non-catalytic reaction
FeSO4 oxidation in Katapack
Non-catalytic process can be enhanced by addition of a heterogeneous catalyst
Diffusion resistance in catalyst particle Gas-liquid equilibria
Kinetic model
c ck 1 + c K
)K
c c cc c( )c
c(k = r FeO
OO
C
3/2wFe
+w¼OFe
+w
¼O
II
III
II
2/12/1
Non-catalytic reaction rate
Catalytic reaction rate
) f (1
c a
a + 1
c c a = r
Fe1
2
O2Fe2
Catalytic and noncatalytic oxidation
0 50 100 150 200 250 3000
1
2
3
4
5
6
7
8
9
10
time/min
Fe(
II)/
wei
ght-
%
Experiments at 4 bar : from top 60oC, 80oC (o), 100oC (x) and 10 bar 100oC (+). Lines by simulation.
Catalyst particles
0 0.2 0.4 0.6 0.8 10.035
0.04
0.045
0.05
0.055
0.06
0.065
0.07
2
510
=
Simulated concentration profiles of oxygen inside catalyst particle
0 0.2 0.4 0.6 0.8 10
0.2
0.4
0.6
0.8
1
1.2
1.4
Catalyst particle coordinate
2
510
J =
Simulated concentration profiles of Fe2+ inside catalyst particle
r + aN aN +
dl
cdD +
dldc
w1
= dt
dcnoncatiLvLiv
bLi2
Li2
LLLi
LL
Li,
aN
dl
cdD+
dt
dcc
dldw+ w
dldc1
= dt
dcv
bLi2
Gi2
GGG
Gi2GiG
1GGi
G
Gi
r + aN aN
dl
cdD +
dldc
w1
= dt
dcinoncat,vLippL2
Li2
LLLi
LL
Li ''''
''
'
'
Dynamic column model
Liquid phase
Gas phase
Liquid inside the net
Gas-liquidmasstransfer
MasstransferThrough thenet
Reaction in particle
Reaction inBulk liquid
Model simulation and verification
0
5
10
15
20
05
1015
2025
0.60.8
11.21.41.61.8
22.22.4
mol/l
timelength
0
0.5
1
1.5
2
2.5
3
0 50 100 150 200 250
time (min)
120 C 4.7 bar kla=0.116 1/s
Independent model verification in a pilot reactor
Concentration of ferrous sulphate
Catalyst reactivation and ultrasound
Deactivation is serious problem in heterogeneous catalysis
- help is needed
The aim of the study:
a) to determine the effect of ultrasound on deactivation kinetics
b) to model quantitatively the effect of ultrasound on kinetics
0 2 4 6
Time
CA
1st
3rd
2nd
4th Batch
Catalyst performance in batch reactor
• The catalyst activity declines at each batch even at low temperatures
• The reason is very often the fouling by organic compounds
• More catalyst is added -> mass transfer limitations enter
• Can ultrasound prolong the catalyst lifetime?
A + H2 -> P
In situ ultrasound equipment
Electricconnection
HornM odifiedRushton
turbine
Pressurizedautoclave
High-pressure autoclave with in situ ultrasonic irradiation system (in-house design) :
Power input 0-100 W
Operating frequency 20kHz
Slurry reactor
Multi-transducer set-up
Generator (0-600W)
20 kHz
Reactor pot inserted
6 transducers
A time-variable
power input
Case studies
Case Catalysts
D-fructose hydrogenation Raney-Ni, Cu/SiO2,
Cu/ZnO/Al2O3
1-phenyl-1,2-propanedione hydrogenation
Pt/SF, Pt/Al2O3 , Pt/ SiO2 ,
Pt/C
D-fructose hydrogenation
CH2OH
C
CH
HC
O
HO
OH
HC OH
CH2OH
H2
CH2OH
CH
CH
HC
HC
CH2OH
HO
HO
OH
OH
CH2OH
HC
CH
HC
HC
CH2OH
HO
OH
OH
OHH2
D-sorbitol
D-mannitol is a low caloric sweetener widely used in pharmaceutical and alimentary industry.
D-mannitol
D-fructose
Reaction conditions
• Pressurised batch autoclave (VL=250ml)
• Stirring rate 1800 rpm
• pH2 = 30 bar
• T=110C
• Nominal ultrasound intensity 130 Wcm-2
• Solvent: deionised water
• Catalyst: Raney-Ni
Catalyst characterisation
The spent Raney-Ni catalyst treated in the absence of ultrasound.
The ultrasonic treated spent Raney-Ni catalyst.
0
20
40
60
80
100
0 20 40 60 80 100 120
time (min)
Con
vers
ion
(%)
3rd reuse
3rd reuse Sono
fresh Sonofresh Silent
Deactivation of re-used catalyst
)( 21 rrdt
dCB
F
F
FC
CX0
1 , tckk
F
F HBeC
C 221 )(
0
tktckkX HB''
21 2)()1ln(
Kinetic modelling
Simple kinetic model
Test of pseudo-first order kinetics. T = 110°C, pH2 = 30 bar. X = conversion of D-fructose.
0
0.5
1
1.5
2
2.5
3
3.5
0 20 40 60 80
reaction time / [min]
-ln
(1-X
)
silent, fresh
silent, 3rd reuse
sono, fresh
sono, 3rd reuse
BHCkk
2'''
k’silent k’sono
fresh 2.27 2.19
3rd re-use 1.06 1.61
min)('catg
mlk
Ultrasound effect and model simulation
Example fit using the graphically obtained rate constants, T = 110°C, pH2 = 30 bar. (Fructose: ○ = silent, ● = ultrasound;
Mannitol: □ = silent, ■ = ultrasound; Sorbitol: ◊ = silent, ♦ = ultrasound).
0 20 40 60 80 100 1200
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
reaction time / [min]
conc
entr
atio
n /
[mol
/l]
3rd reuse
Mannitol & Sorbitol
Fructose
1-Phenyl-1,2-propanedione hydrogenation
O
O
O
OH
O
OH
O
HO
O
HO
OH
HO
(B)
(C)
(D)(E)
OH
HO
HO
OH
(I) (F)
(G)(H)
(A)
OH
HO
Used for the synthesis of several pharmaceuticals e.g.
ephedrine...
Reaction conditions
Pressurised batch autoclave (VL=200ml)
• Stirring rate 2000 rpm
• pH2 = 10 bar
• T=15C
• Nominal ultrasound intensity 78 Wcm-2
• Catalyst modifier (M): cinchonidine cM = 0.1mg/ml
• Solvents: toluene, methyl acetate, mesitylene
N
N
OHH
Catalyst modifier cinchonidine
The spent Pt/SF catalyst treated in the absence of ultrasound (SEM image).
The ultrasonic treated spent Pt/SF catalyst (SEM image).
Catalyst characterization
Catalyst deactivation – experiments in a fixed bed
0
10
20
30
40
0 20 40 60 80
Time-on-stream (min)
c (m
mo
l l-1
)
A
R
S
Solvent and ultrasound effect on conversion on Pt/Silica fibre catalyst
0
20
40
60
80
100
0 20 40 60 80 100 120
time (min)
Con
vers
ion
(%)
US effect
US effect
US effect
Methyl acetate
Toluene
Me
Mesitylene
Hydrogenation kinetics of 1‑phenyl‑1,2‑propanedione
0.000
0.005
0.010
0.015
0.020
0.025
0 20 40 60 80 100 120
time (min)
c (m
ol /
dm
3 )
0.000
0.005
0.010
0.015
0.020
0.025
0 20 40 60 80 100 120
time (min)
c (m
ol /
dm
3 )
(R )- enantiomer
(S )- enantiomer
Hydrogenation kinetics of 1‑phenyl‑1,2‑propanedione (A) at 15°C and 6.5 bar hydrogen
AB (R)
C (S)
H2
H2
B + C
B
C
AB
C
2
' HAjj cckr
))1(exp((
1
1'0
' tkdkk jj
dUS kk
A + * A* A’* P + * kd US
Modelling of ultrasound and deactivation
Parameter values
Solvent kd
(100*min-1)
kd,US
(100*min-1)
kd-kd,US
(100*min-1)
Toluene 1.74 1.22 0.52
Mesitylene 14.1 13.0 1.1
Methyl acetate
1.45 1.07 0.39
Data fitting and model simulation
Batch reactor
0 20 40 60 80 100 1200
0.002
0.004
0.006
0.008
0.01
0.012
0.014
0.016
0.018
0.02
US
No US
time (min)
c (m
ol/l)
A
B
C
DE A
B
C
DE
A: 1-Phenyl-1,2-propanedione, B: (R)-1-hydroxy-1-phenylpropanone, C: (S)-1-hydroxy-1-phenylpropanone, D+E: (R)+(S)-2-hydroxy-1-phenylpropanone
0 20 40 60 80 100 1200
0.002
0.004
0.006
0.008
0.01
0.012
0.014
0.016
0.018
0.02
c (m
ol/l)
time (min)
A
BC
D+E
A, no US
A, US
Continuous, dynamic fixed bed with axial dispersion
Liquid phase
Gas phase
The effectiveness factor ( ) is obtained from the pellet model ( ).
Special cases: : plug flow reactor all flows zero : batch reactor
GVGiGi
GGGi
GGGGi N
z
c
z
cPe
t
c /)()( 12
21
BieiLVLiLi
LLLi
LLLLi rN
z
c
z
cPe
t
c
/)()( 12
21
eiiN
GL PePe ,),( GL
C
B
Dynamic modelling of continuous bed
Non-steady state kinetics in continuous fixed bed
c (m
ol/d
m-3)
Experiences from ultrasound
Acoustic irradiation
• Can sometimes improve reaction rate and selectivity
• Prevents catalyst deactivation by surface cleaning and smoothening
• Effects are solvent dependent
• Catalyst and reaction specific effects are visible
• The applications are not limited to catalysis –
the approach works for liquid-solid reactions
Conclusions and future aspects
Reaction intensification is a part of process intensification – keep the entire process in mind
Fundamental understanding on kinetics, thermodynamics, flow structures should be the basis of reaction intensification
A lot of reactor and catalyst structures are available – they shoud be evaluated critically
Intensification methods are very promising, but scale-up is a challenge Implementation of catalysts is an intensification approach as such Active search for new application areas is needed More imagination is needed
A structured reactor
Design by Victor Vasarely (1908-1997 )A famous Hungarian-French painter
”Colours are the vitamines of our life”
Art shows the way
Thank you for your kind attention
Laboratory of Industrial Chemistry and Reaction Engineering
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