Aspects on reaction intensification

Åbo AkademiLaboratory of Industrial Chemistry

and Reaction Engineering

FI-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 Products Process

Process intensification

Intensification methods

Ultrasonic techniques

Microwave techniques

Integrated reaction and separation

Reactions under extreme conditions

Unsteady state operation

Enhancement of mass and heat transfer...

Process intensification

Intensification equipment

Structured reactors

(monoliths, foams, fibre structures, columns)

Reactors with internal heat exchangers

Microreactors

Equipment 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 molecules Chemical 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 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 image SEM image

4 nm 5 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 S

iS

pipi 1

j

jjiji aRr

Reaction, diffusion and catalyst

deactivation in porous particles

Particle model

Rates

Separable and reversible deactivation kinetics

tk

jjjjjeaaaa

*

0

*

1,1 1

1

'1*

0

*

ntnkaaaa nj

n

jjj

Fresh catalyst sample Recycled catalyst sample

Raney-

Nickel

Catalyst

Porous particle model

dr

dcDN i

eii

dr

dc

r

s

dr

cdDaR

dt

dc iieijjijpp

i

2

21

, where Dei=(p/p)Dmi

0dr

dci0r

Rcckdt

dcD iiLi

Rr

iei

Rr

Boundary conditions

Batch reactor

GLGLipii aNaN

dt

dc

RcckN iiLii

GiLi

i

b

Lii

b

GiGLi

kk

K

cKcN

1

Liquid phase mass balance

Liquid-solid flux

Gas-liquid flux

Example systems

Hydrogenation of

Citral

Lactose O O

OH

OH

OH

OH

HO

OHOH

OH

OH

Lactose Lactitol

O O OHOH

OH

OH

HO

OHOH

OH

OH

LactulitolLactulose

O

OH

OH

HO

OH

OH

Galactose

+Glucose

OH

OH

OH

HO

OH

OH

Galactitol

OH

OH

OH

OH

OH

HO

Sorbitol

H2

H2

H2

H2

H2

Isomerization

OHˉ

Hydrolysis

O

O

O

OHHO

OH

OH

HO

HO

HO OH

O

O

O

OH

OH

OH

OH

HO

OHOH

OH

Lactobionic acid

(Na-salt)

Dehydrogenation

Hydrogenation

O

OH

OHHO

OH

OH

O

OH

O OHOH

OH

OH

HO

OHOH

OH

O

O O

OH

OH

OH

OH

HO

OHOH

OH

OH

O O

OH

OH

OH

OH

HO

OHOH

OH

OH

Lactose Lactitol

O O OHOH

OH

OH

HO

OHOH

OH

OH

O O OHOH

OH

OH

HO

OHOH

OH

OH

LactulitolLactulose

O

OH

OH

HO

OH

OH

Galactose

+Glucose

OH

OH

OH

HO

OH

OH

OH

OH

OH

HO

OH

OH

Galactitol

OH

OH

OH

OH

OH

HOOH

OH

OH

OH

OH

HO

Sorbitol

H2

H2

H2

H2

H2

Isomerization

OHˉ

Hydrolysis

O

O

O

OHHO

OH

OH

HO

HO

HO OH

O

O

O

OHHO

OH

OH

HO

HO

HO OH

O

O

O

OH

OH

OH

OH

HO

OHOH

OH

O

O

O

OH

OH

OH

OH

HO

OHOH

OH

Lactobionic acid

(Na-salt)

Dehydrogenation

Hydrogenation

O

OH

OHHO

OH

OH

O

OH

OHHO

OH

OH

O

OH

O OHOH

OH

OH

HO

OHOH

OH

O

Modelling results Citral 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

lative c

on

cen

tratio

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 lactitol Intrinsic 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 (

mol/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 profiles

inside catalyst particle

with different particle sizes

Surface Center

Lactose

Lactitol

0 200

400 600

0

0.5

1

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 200

400 600

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

center x x

4FeSO4 + O2 + 2HSO-4 + 2H3O

- ®

2Fe2(SO4)3 + 4H2O

Proceeds as a gas-liquid reaction but catalyst helps

Catalyst: 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

2/1

2/1

Non-catalytic reaction rate

Catalytic reaction rate

) f (1

c a

a + 1

c c a = r

Fe

1

2

O2Fe2

Catalytic and noncatalytic oxidation

0 50 100 150 200 250 300 0

1

2

3

4

5

6

7

8

9

10

time/min

Fe(I

I)/w

eig

ht-

%

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 1 0.035

0.04

0.045

0.05

0.055

0.06

0.065

0.07

2

5 10

J =

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

=

Simulated concentration

profiles of Fe2+ inside catalyst

particle

r + aN aN +

dl

cdD +

dl

dcw

1 =

dt

dcnoncatiLvLiv

bLi2

Li2

LLLi

L

L

Li,

aN

dl

cdD+

dt

dcc

dl

dw+ w

dl

dc1=

dt

dcv

bLi2

Gi2

GGG

Gi2GiG

1GGi

G

Gi

r + aN aN

dl

cdD +

dl

dcw

1 =

dt

dcinoncat,vLippL2

Li2

LLLi

L

L

Li ''

'''

''

'

Dynamic column model

Liquid phase

Gas phase

Liquid inside the net

Gas-liquid

masstransfer

Masstransfer

Through the

net

Reaction in

particle

Reaction in

Bulk 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

Electric

connection

HornM odified

Rushton

turbine

Pressurized

autoclaveHigh-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

OH

H2

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)

Co

nve

rsio

n (

%)

3rd reuse

3rd reuse Sono

fresh Sonofresh Silent

Deactivation of re-used catalyst

)( 21 rrdt

dCB

F

F

F

CC

X0

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]

concentr

ation /

[m

ol/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 (

mm

ol 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)

Co

nve

rsio

n (

%)

US effect

US effect

US effect

Methyl acetate

Toluene

M

e

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 (

mol /

dm

3)

0.000

0.005

0.010

0.015

0.020

0.025

0 20 40 60 80 100 120

time (min)

c (

mol /

dm

3)

(R )- enantiomer

(S )- enantiomer

Hydrogenation kinetics of 1-phenyl-1,2-propanedione (A) at 15°C and

6.5 bar hydrogen

A B (R)

C (S)

H2

H2

B + C

B

C

A B

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 (

mol/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 (

mol/l)

time (min)

A

B C

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 /)()( 1

2

2

1

BieiLVLiLi

LLLi

LLLLi rN

z

c

z

cPe

t

c

/)()( 1

2

2

1

eiiN

GL PePe ,),( GL

C

B

Dynamic modelling of continuous bed

Non-steady

state kinetics

in continuous

fixed bed

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