Process Intensification through Multifunctional reactors

Sanjay MahajaniSanjay MahajaniProfessor of Chemical Engineering

Indian Institute of Technology Bombay

20th December, 2011.

What are multifunctional reactors ?What are multifunctional reactors ?

The term multifunctional reactor can be defined f fas a reaction equipment in which performance of reaction is synergetically enhanced by means of integrating one or more additional process functions

This additional function can be a separation step

RDResearchGroup

Multifunctional reactors:Combine reaction with separation

• Reactive Distillation• Reactive Chromatography• Membrane reactors•• …

Concept of Reactive DistillationConcept of Reactive Distillation

We can improve equilibrium conversionWe can improve equilibrium conversionby removing product in the reactorby removing product in the reactorby removing product in the reactorby removing product in the reactor..

(Le Châtelier’s principle)(Le Châtelier’s principle)

A + B ↔ C + DA + B ↔ C + D

If we remove C the equilibriumIf we remove C the equilibriumconversion to product D increasesconversion to product D increases

CD

xxxxK BAxxRD

ResearchGroup

If the volatilities are right, If the volatilities are right, we can remove a component by vaporizationwe can remove a component by vaporization

C (A, B, D)

A

B A + B ↔ C + DA + B ↔ C + D

A, B, D

Improved yieldImproved yieldRD

ResearchGroup Concept of Reactive Distillation

P id fl l f f d iP id fl l f f d iProvide reflux to prevent loss of feed in vaporProvide reflux to prevent loss of feed in vapor

CC

A, B, D

A

BB

A, B, D

We can strip the product and recycle the feeds We can strip the product and recycle the feeds p p y fp p y f(if the volatilities are right)(if the volatilities are right)

CC

A A, B, A

B

, ,D

A, BA, B

DD

… this is starting to look like a column !

DReactive distillation

RD Process for methyl acetate

methanol + Acetic Acid methyl acetate + water

AcOH

MeOAc

1

AcOHMeOHH2SO4

H2SO4

AcOHTo impurity removal columns

2MeoAc

MeOH

Return form impurityremoval columns

3 Water

MeOH

H2O

4Heavies

Water + H2SO4

2

RD performs difficult separations RD

ResearchGroup

Way back in 1869…

Cooler

NH3+CO2 for absorber

Cooler

Filter liquorLiquor preheater

Reactions takes place close to boiling

Strippper (NH4)2CO3 = 2NH3 + CO2 + H2O

close to boiling conditions

Prelimer

Lime milk

Design is based on the Concept of Reactive Distillation !!

Distillation Column

(NH4)2SO4 + CaO= 2NH3 + CaSO4 + H2O2NH4Cl+ CaO= 2NH3 + CaCl2 + H2O

Low Pressure Steam

Ammonia Recovery in Solvay ProcessRD

ResearchGroup Solvay Process

Publications on Reactive Distillation90

Publications on Reactive Distillation

70

80 Papers

Patents

50

60

70

40

50

20

30

0

10

01970 1975 1980 1985 1990 1995 2000

RDResearchGroup (Hiwale et al., Int. J. Chem React. Engg. 2004)

R ti Di till ti ibl b fitReactive Distillation: possible benefits

• Capital Savings• Improve Selectivity 

• Reduce Raw Materials Usage • Reduce Byproducts Prevent Pollution 

• Reduce Energy Use • Handle Difficult Separations• Handle Difficult Separations 

– Avoid Separating Reactants – Eliminate/Reduce Solvents /

• “Beat” Low Equilibrium Constants • Heat integration benefits• Longer catalyst life

Constraints: Volatilities are not right; g ;Complexity in design and operation

Butyl acetate in RD

H+

Butyl acetate in RD

CH3COOH + C4H9OH C4H9COOCH3 + H2OH+

Formation of heterogeneous Minimum Boiling ternary Azeotrope

butanolrecyclerecycle

Acetic acid +

Butanol Pre-Reactor

water

waterbutanol

Acetic acid +Butanol

butanol+ water

Butyl acetate Butyl acetateButyl acetate

The energy consumption in the RD process is expected to be 40% less

Work Elements of RD Process Development

E i t f E i t VLE d tExperiments for reaction kinetics and regression

Experiments on VLE data generation and regression

Conceptual Design and Synthesis

Hardware selection

Steady State and Dynamic Simulation

Column Experiments

Optimizationand Control

Case StudyCase Study Synthesis of 2-Ethylhexyl Acetate

Reaction Scheme:

Acetic Acid + 2-ethyl hexanol 2 ethyl hexyl acetate + water

Applications:

Good solvent power Coatings additives in cleaners improves flow and filmGood solvent power, Coatings, additives in cleaners, improves flow and film formation

Alcohol is heavy and boiling temperatures would exceed thermal stability limit of catalyst

Conventional Process

Entrainer Based Reactive DistillationEntrainer Based Reactive Distillation EBRD

Entrainer is separated in l b kdecanter and recycled back.

AdvantagesE h d ti t Enhanced reaction rates

Overcomes limitations due to distillation boundaries

Helps in lowering down reboiler and column temperaturetemperature 

Better protection against catalyst deactivation

Reduced catalyst loading

Th d i (Ph ilib i )Thermodynamics (Phase equilibrium)

UNIQUAC‐HOC selected forQthermodynamic model

Parameters for the thermodynamic model taken from Aspen Data Bank.from Aspen Data Bank.

VLE experiments conducted to pdetermine binary interaction parameters of component pairs for which information not pavailable in Aspen Data Bank.

Generated T-xy dataGenerated T xy data

Toluene ‐ 2‐ethylhexyl acetate 

Acetic  Acid – 2‐ethylhexyl acetate 

Txy data continued…Txy data continued…

• toluene – 2‐ethylhexanol  2‐ethylhexanol – 2‐ethylhexyl acetateacetate 

Regressed binary interaction parametersRegressed binary interaction parameters

Component i 2-EHOH TOLUENE AA TOLUENE

Component j 2-EHAC 2-EHOH 2-EHAC 2-EHAC

Temperature units K K K K

aij 1 81989793 2 90232722 4 03069111 -4 92152717aij 1.81989793 2.90232722 4.03069111 4.92152717

aji -0.617807244 -4.67110786 -9.88579185 5.38982778

bij -1236.45922 -956.324435 -1594.93966 2249.1795

bji 548.659258 1490.66902 3828.60687 -2461.82773

Azeotropes in presence of entrainer*Azeotropes in presence of entrainer

Components Water Toluene AA 2EHOH 2EHAc Boiling Pt. Azeotrope

t% (°C)wt% (°C)

Water-Toluene 19.55 80.45 --- --- --- 84.29 Heterogeneous

Water-2EHOH-2EHAc 75.22 --- --- 8.99 15.79 98.97 Heterogeneous

Water-2EHAc 75 75 --- --- --- 24 25 99 09 HeterogeneousWater 2EHAc 75.75 24.25 99.09 Heterogeneous

Water-2EHOH 81.84 --- --- 18.16 --- 99.17 Heterogeneous

T l AA 66 44 33 56 103 99 HToluene-AA --- 66.44 33.56 --- --- 103.99 Homogeneous

2EHOH-2EHAc --- --- --- 78.85 21.15 183.96 Homogeneous

* from Aspen Data Bank

Residue Curve Map (RCM) for the system: (a) 2-ethylhexanol toluene and water; (b) 2 ethyhexylethylhexanol, toluene and water; (b) 2-ethyhexyl

acetate, 2-ethylhexanol and water.

(a)                                                                                            (b)

Reaction kinetics

Conc. based modified LHHW model

2

2

2 22

( )(1 )

i f AcH EHOH b EHAc H Oii

cat m AcH w H O

k C C k C CdCVrM dt K C K C

22 2( )i f AcH EHOH b EHAc H Oik a a k a adxnr

Activity based modified LHHW model

)/exp( 00 RTEkk fff

2

2(1 )icat m AcH w H O

rM dt K a K a

Where,)/exp( 00 RTEkk bbb

Optimization problemActivity – UNIQUAC model

22

1 1 1

minijMNDyn Nmeans

ijk j ijk ikji j k

SSE W z t z

p pAspen custom modeler

Column Experimentsp

Total height = 3.18m Reactive section 1.38 m Reactive Packing : 

K t k S fill d ithKatapak‐S filled with Amberlyst‐15 IER (NTSM = 3)

Non‐reactive Packing: HYFLUX (NTSM = 8)El i ll h d Electrically heated Reboiler

Comparison of experiment and simulation results for one of the representative run : Reboiler Duty=120W; Molar Feed Ratio = 1:1;representative run : Reboiler Duty 120W; Molar Feed Ratio   1:1; 

AA +Tol at Stage No.9;2EHOH at Stage No. 12 

19 19 19

15

17 AA-Sim

AA-Expt15

17Toluene-Sim

Toluene-Expt15

172EHOH-Sim

2EHOH-Expt

11

13

No.

11

13

No.

11

13

No.

7

9Sta

ge

7

9Sta

ge

7

9Sta

ge

5

7

5

7

5

7

1

3

0 0 2 0 4 0 6 0 8 1

1

3

0 0 2 0 4 0 6 0 8 11

3

0 0 2 0 4 0 6 0 8 1

0 0.2 0.4 0.6 0.8 1

Mole Fraction 0 0.2 0.4 0.6 0.8 1

Mole Fraction0 0.2 0.4 0.6 0.8 1

Mole Fraction

Comparison of experiment and simulation ltresults

19 19 19

15

172EHAc-Sim

2EHAc-Expt 15

17Water-Sim

Water-Expt 15

17 Simulation

Experiment

11

13

No.

11

13

No.

11

13

No.

7

9Sta

ge

7

9Sta

ge

7

9Sta

ge

5

7

5

7

5

7

1

3

0 0.2 0.4 0.6 0.8 11

3

0 0 2 0 4 0 6 0 8 11

3

80 110 140 170 200

0 0.2 0.4 0.6 0.8 1

Mole Fraction 0 0.2 0.4 0.6 0.8 1

Mole Fraction80 110 140 170 200

Temperature (C)

Effect of different parameters on conversion

EBRD configurationg

mol fraction 2EHOH negligible AA negligible

Decanter aqueous stream

organic stream as

fl

2EHAc negligibleWater 0.7003 Toluene 0.2997 2.1401 kmol/hr

streamreflux

2-ethylhexanol 1.5 kmol/hr

2EHOH negligible AA negligible 2EHAc negligible Water 0 9999

2EHOH negligible AA negligible 2EHAc negligible Water 0 0029

acetic acid 1.5 kmol/hr

Water 0.9999Toluene negligible 1.4971 kmol/hr

Water 0.0029Toluene 0.9971 0.6430 kmol/hr

entrainer makeup0.001 kmol/hr

2EHOH 2.16e-3 AA 2.08e-3

final product

2EHAc 0.9952 Water negligible Toluene negligible 1.5039 kmol/hr

Conventional vs Proposed RD processConventional vs Proposed RD process

Conventional Process

Comparison of proposed process with ti lconventional process

Proposed RD Process Conventional Process

• Steam consumption per kg product =0.43

• Steam consumption per kg product =1.46

• Single RD column is sufficient

• Additional separation columns are needed

• Easy operation • Catalyst separation required

Diisobutene in RD

Parameter Value

Column diameter, ID, cm 5

IB + IBDIBDIB + IBTIB

•Conventional reactors need selectivity enhancer•RD works without enhancers•RD performs much better than

Column height, m 3

Height of reactive section, m 1

Total catalyst loading, gm 30

Height of non-reactive section, m 2

Number of theoretical stages in the 3 DIB + IBTIBTIB + IBTEBIB + 2-Buc-DIM1 Bu2 Bu

pconventional reacting systems (selectivity: 80% in lab)

Talwalkar et al., IECR, 2005, 2007Kamath et al. IECR, 2005, 2006

Number of theoretical stages in the reactive zone

3

Number of non reactive stages 16

Operating pressure, atm 10

Feed pump rating, lit/hrs 0 to 3

Reboiler holdup lit 2 1-Bu2-BuReboiler holdup, lit 2

Aldol Condensation of Acetone in RDAldol Condensation of Acetone in RD

7

8

0.8

1

ty

0.02 kg/m of catalyst conc.0.04 Kg/m of catalyst conc.Batch reactor

5

6

ber Reactive

stages0.4

0.6

DAA

sele

ctiv

it

Simulation

4

5

Stag

e nu

m

AcetoneDAA

0

0.2

0 0.1 0.2 0.3

C i

D

5m

2

3

S DAAMOWaterSimulation

Conversion

It is for the first time selectivity of

10 0.2 0.4 0.6 0.8 1

Mole fraction

the order of 50-60% with acid catalyst is reported for this reaction.

Mole fraction

3kDAA MO + H O 3 DAAk ar r

2Ac 1 Ac 2 DAAr k a k a

Acetone DAA

Concentrations of DAA and MO are very low on reactive stages

2DAA MO + H O DAA Ac 2

w w

r r1 k a

Reactions studied in IIT-B

• Esterifications:Butyl acetate, 2-ehtyl hexyl acetate, cellosolve acetate, triacetin, ethylene glycol diacetate, methyl acetate (recovery of acetic y g y , y ( yacid), lactate esters

• Acetalization:Acetalization: 2-methyl pentenone, glycerol acetals

• Aldol condensation:Diacetone alcohol, aldol of cyclohexanone, y

• DImerization: isooctene

Reactive chromatographyg p y

Process development steps in Reactive chromatography

Adsorption isotherms

R ti Ki ti

Pilot scale FBCR experiments

Reaction Kinetics

Conceptual Design :Triangle theory

SMBR simulations

Process Optimisation and further integration

Fixed Bed Chromatographic Reactor (FBCR)g p ( )

ConstructionC t l t l Catalyst also as adsorbent

Residence time as a critical parameterp

Wave phenomena within the reactorwithin the reactor

Use in non reactive binary adsorptionbinary adsorption isotherm experiments

What is reactive chromatography?What is reactive chromatography?

A is taken in large excess

Isotherm measurement Binary adsorption (breakthrough) experimentsBinary adsorption (breakthrough) experiments

Acetic acid- 2-ethylhexyl acetate, T = 800CAcetic acid- water, T = 800C

2-ethylhexanol 2-ethylhexyl acetate

Flow rate = 2ml/min, T = 800C

2-ethylhexanol 2-ethylhexyl acetate

Flow rate = 4ml/min, T = 800C

Adsorption parameter estimation

Non-reacting Binary mixtures possible areAcetic acid – water, Acetic acid – 2-ethylhexyl acetate2-ethylhexanol – 2-ethylhexyl acetate

Objective function LSQNONLIN Function was2

,exp ,1 1

( ) min ( )N m

ij ij mi j

F x x x

LSQNONLIN Function was used using MATLAB Solver

Parameters of Multicomponent Langmuir isotherm (8-parameter)

Components K (cm3/mol) (m mol/gm)Components K (cm /mol) (m mol/gm)Acetic acid 413.20 22.352-ethylhexanol 284.52 7.42-ethylhexyl acetate 196.12 2.55Water 1232.02 45.3

Affi it O dAffinity Order:Water > Acetic acid > 2-ethylhexanol > 2-ethylhexyl acetate

Parity plots for mole fraction of acetic acidy p

0 80.9

1

0 80.9

1

0.50.60.70.8

odel

ed

0.50.60.70.8

odel

ed

0.20.30.4M

o

0.10.20.30.4M

o

00.1

0 0.5 1observed

00.1

0 0.5 1

Observedobserved

Conc. based LHHW model Activity based LHHW model

• Choice of model is normally governed by how well the kinetic data is explained

• Modified LHHW model explains the data very well

Modeling approach for RCModeling approach for RC

Assumptions: Langmuir adsorption isotherm governs the

multicomponent adsorption phenomenamulticomponent adsorption phenomena. Isothermal operation. Axial dispersion is accounted for.

Resin phase concentration is in equilibrium Resin phase concentration is in equilibrium with the bulk phase liquid concentration.

Superficial liquid velocity is constant.Swelling effect of the resin is neglected Swelling effect of the resin is neglected.

FBCR: Experimental setup and resultsp p

1

0.6

0.8

actio

n

AcH

2EHOH

2EHAc

0.2

0.4

Mol

e fra Water

00 100 200 300 400

Time(mins)

Separation zone

Reactive Separation

Steady state

(R t h i ht 70 t di t 1 5 t l t 39 46

zone pzone Reactive

zone

(Reactor height = 70 cm, reactor diameter = 1.5 cm, catalyst = 39.46 gms,feed flow rate = 1 ml/min, Mole ratio (2EHOH: AcH = 1:1), T = 800C)

Simulated moving bed reactor (SMBR)Simulated moving bed reactor (SMBR)

Construction and workingworking

Catalyst and d b tadsorbent

Switching time gand cycle of an SMBRSMBR

Virtual solids velocityvelocity

Separation within the reactor

SMBR : Working principleg p p

Desorbent (AA)Raffinate (A+D)

3 4

Section IVDesorbent (AA)Raffinate (A+D)

Section IV

2 5

Direction of Port switching and fluid flow

Section III

Feed (A+B)

Raffinate (A+D)

Soldir

Fluid dire c

1 6Section II

( )

Extract (A+C)

lid flow

rection

flow

ction

8 7

Feed (A+B) Section IIExtract (A+C)

Section I

Desorbent (A) Extract (A C)

True moving Bed Simulated moving Bed reactorTrue moving Bed g

SMBR : Working principleSMBR : Working principle

Eluent (A) Recycling

Feed (A+B)

II III IVI

Feed (A+B)

Adsorbent Recycling

Extract (A+C) Raffinate (A+B)

The Triangle Theoryg y

* net fluid flow rate(1 ) net solid flow rate

j colj

Q t Vm

V

(1 ) net solid flow ratecolV

Concentration profile at the end of switch atConcentration profile at the end of switch at cyclic steady state

Raffinate Port

Extract Port

•X-axis depicts the position along the column

Feed

p p g

• Length is relative the nodes which are physically moving in every switch

•Conc. profile remains unchanged due to cyclic steady state in successive switches

SMBR downstream processingSMBR downstream processing

Section IVDesorbent (A)Raffinate (A+D) A

3 4

2 5D

1 6

Direction of Port switching and fluid flow

8 7 C

Feed (A+B) Section IIExtract (A+C)

C

makeup

AMuch of the cost lies in distillative separations

Comparison RC and RD in terms of energyComparison RC and RD in terms of energy consumption (kg of steam / kg of product)

RC + Conventional post-processing

RD

RemarksSolvent

Acetic Acid Alcohol

Methyl Acetate

Methyl Acetate-Acetic Acid 0.29

Not feasible 0.48 RD. is favorable

Water-Acetic Acid 2.06

Total Steam consumption 2.35

Ethyl Acetate-Acetic Acid 0.74

RC. and RD are

Water-Acetic Acid 1.74

Total Steam consumption 2.48

Ethyl Acetate Not feasible 1.97 comparableAlternative 1.74

Iso-Propyl Acetate-Acetic Acid 0.82

Water-Acetic Acid 1.59

Iso-Propyl Acetate Not feasible 1.95RC and RD are comparable

Total Steam consumption 2.41

Alternative 2.05

Butyl Acetate-Acetic Acid 2.9 3.85

Water-Acetic Acid 0 74 0 84

Butyl Acetate 0.68 RD is favorable

Water-Acetic Acid 0.74 0.84

Total Steam consumption 3.64 4.69

Alternative 3.16 -----

2-Ethylhexyl Acetate-Acetic

2-Ethylhexyl Acetate

y yAcid 0.39

Not feasible 0.43 RD is favorable

Water-Acetic Acid 0.92

Total Steam consumption 1.31

Acknowledgementg

Research Scholars:

Sandip Talwalkar

Suman Thotla

Amit Hasabnis

Prafulla Patidar

Rahul Bhat

Amit Agarwalg

Bhoja Reddy

Funding Agencies:

DST, Schenctady Herdillia, VW foundationDST, Schenctady Herdillia, VW foundation