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Coupled esterification reaction in ionic liquids and product recovery by pervaporation

P. Izák1, N.M.M. Mateus2, C.A.M. Afonso2, J.G. Crespo2

1Department of Separation Processes, Institute of Chemical Process Fundamentals, Rozvojová 135, 16502 Prague 6, CZ2Institute of Chemistry, University of Rostock, Albert Einstein Str.3a, 18059 Rostock, Germany3Institute of Chemical Sciences and Engineering, Swiss Federal Institute of Technology, 1015 Lausanne, Switzerland4Department of Physical Chemistry, Institute of Chemical Technology, Technická 5, 16628 Prague 6, Czech Republic

The aim

• Conversion enhancement of esterification reactions taking place in RTILs by pervaporation

• Modeling of the esterification reaction coupled with

pervaporation

• Prediction of process variables influence on the esterification reaction

Room Temperature Ionic LiquidsRoom Temperature Ionic Liquids

N N R Cl+ Reflux 80ºC24 h

HX(X

_ = PF6

_, BF4

_ )

RT – 24hN+ N R +Cl - N+ N R X -

Non-measurable vapour pressure Green solvent

High ionic conductivity and thermal stability

Ability to solubilize a large range of organic molecules and transition metal complexes

(R= methyl group, R= octyl group, R= decyl group), X _

= PF6

_

, X _

= BF4 _

)

Do not permeate through either organophilic or hydrophilic dense membranes

Possibly an environmentally benign alternative to classical organic solvents

High viscosity and low heat transfer

Purification of ionic liquids

Room Temperature Ionic LiquidsRoom Temperature Ionic Liquids

Experimental

Hydrophobic RTIL [bmim] [PF6] at temperatures over 50°C - hydrolysis producing HF and PO4

3-

The selected “dried” [bmim] [BF4] had viscosity 26 cP at 60°C

Due to crystallization on the lid of the vessel, a 50% excess of (-)-Borneol was used

[bmim] [BF4]+ CH3COOH H2O + p-TsOH 60°CA B EW

Experimental Esterification in closed vessel with minimized headspace

• Water content in the reaction mixture was determined by automatic Karl-Fisher titration (Aquapal III)

• Esterification reaction was monitored by GC (CP-9001) using a FFAP polar capillary column

• Pervaporation membrane for water removal – PVA membrane PERVAP® 2205, SULZER (suitable for organic acids without limitation)

Pervaporation set-up

Pervaporation Pervaporation experimentexperiment – – standard laboratory standard laboratory pervaporation set-up pervaporation set-up with effective with effective membrane area of membrane area of 100 cm100 cm2 2 ; downstream ; downstream pressurepressure pp = 0.06 mbar = 0.06 mbar

Reaction vessel

Cold trap

Retentate

Permeate

Permeate

Vacuumpump

Feed

Thermostat

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Time (h)

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nc

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e r

ea

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r (m

ol/L

)

W - Water

A - Acetic acid

E - (-)-Bornyl acetate

Esterification at 60°C

BA

WE

k

kK

b

f

WEBA cat, kf

kb

038.0629.0 K

Model assumptions

The consumption of acetic acid can be expressed by:

WEbBAfA CCkCCk

dt

Cd (1)

    1. Isothermal operation   2. Ideal mixing for all reactants in reactor 3. Negligible permeation of reactants through the membrane

)(K

NNNNk

dt

dNV

dt

dVN EW

BAfA

A (2)

Moles of acetic acid consumed during esterification can be expressed as:

Differential equations for modelingDifferential equations for modeling

For the other components it can be derived:

(3)

(4)

(5)

(-)-Borneol:(-)-Borneol:

(-)-Bornyl acetate:(-)-Bornyl acetate:

Water:Water:

dt

dN

dt

dN AE

RVJdt

dN

dt

dNW

AW

RVJdt

dN

dt

dNB

AB

V

SR Mwhere where RR is the process variable: is the process variable: (6)

Volume change in the reactor

Taking into consideration that the ionic liquid does not permeate Taking into consideration that the ionic liquid does not permeate through the PVA membrane, through the PVA membrane, dV/dtdV/dt can be expressed by:can be expressed by:

(7)

All differential Eqs. (2-5, 7) were solved by the least square All differential Eqs. (2-5, 7) were solved by the least square method using Scientist software. method using Scientist software.

2)V/NJ/N-R(Jdt

dVBBWW

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Water Acetic acid (-)-Bornyl acetate

kf = (2.72 ± 0.13)×10-4 m3 mol-1 h-1

Fitting of esterification reaction

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Water - PV Acetic acid - PV (-)-Bornyl acetate - PV

Esterification coupled with pervaporation

Jb = 8.96×10-3 mol m-2 h-1

Drying of Drying of [bmim] [BF[bmim] [BF44]] by PV by PV

y = -1.1933x2 + 2.4169x

R2 = 0.9857

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1.0

1.2

0.0 0.2 0.4 0.6 0.8

Concentration of H2O in [bmim] [BF4] (mol/L)

Mo

lar

Flu

x o

f H

2O

(m

ol/m

2/h

)

T = 60°C

Simulation of esterification coupled with pervaporation

Parameters used for the simulation:Parameters used for the simulation:.........................................................

JJww = = (-1.19(-1.19[W][W]2 2 ++ 2.422.42 [W][W] )) mol mmol m-2 -2 hh-1-1; ; JJbb = = 8.968.96×10×10-3 -3 molmol mm-2 -2 hh-1-1; ; ....K

KK = (0.629 = (0.629 ± 0.038)± 0.038); ; kf kf = (2.74 ± 0.13) ×10 = (2.74 ± 0.13) ×10- 4- 4 m m33 mol mol-1 -1 hh-1-1;; RR == 48 m 48 m-1-1

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(mo

l/L

) Water - PV Acetic acid - PV (-)-Bornyl acetate - PV

Comparison of esterification with and without pervaporation

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)Water Water - PV Acetic acid

Acetic acid - PV (-)-Bornyl acetate - PV (-)-Bornyl acetate

Effect of SEffect of SMM/V ratio on water concentration in the reactor/V ratio on water concentration in the reactor

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Esterification (R = 48 m -1)

R = 200 m -1

R = 1000 m -1

Esterification + PV (R = 48 m -1)

R = 500 m -1

R = 1500 m -1

Effect of Effect of SSMM/V/V ratio on conversion to ratio on conversion to (-)-Bornyl (-)-Bornyl acetateacetate in the reactor in the reactor

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(%

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Esterification (R = 48 m -1)

R = 200 m -1

R = 1000 m -1

Esterification + PV (R = 48 m -1)

R = 500 m -1

R = 1500 m -1

• Thanks to pervaporation, the reaction conversion increased from 22.0% to 44.4% (increase by 102%)

• Numerical simulation and experimental results showed a good agreement

• The process variable SM/V has a significant impact on the esterification conversion

Conclusions

Acknowledgement

• This research was supported by Marie Curie Intra-European and Marie Curie Reintegration Fellowships within the 6th European Community Framework Programme and by Purkyne Fellowship from Czech Academy of Science.

• Thank you for your attention!