Coupled esterification reaction in ionic liquids and product

Coupled esterification reaction in ionic liquids and product recovery by pervaporation P. Izák 1, N. M. M. Mateus 2, C. A. M. Afonso 2, J. G. Crespo 2 1 Department of Separation Processes, Institute of Chemical Process Fundamentals, Rozvojová 135, 16502 Prague 6, CZ 2 Institute of Chemistry, University of Rostock, Albert Einstein Str. 3 a, 18059 Rostock, Germany 3 Institute of Chemical Sciences and Engineering, Swiss Federal Institute of Technology, 1015 Lausanne, Switzerland 4 Department of Physical Chemistry, Institute of Chemical Technology, Technická 5, 16628 Prague 6, Czech Republic http: //www. icpf. cas. cz/

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 Liquids _ _ (R= methyl group, R= octyl group, R= decyl group), X = PF 6 , X = BF 4 ) N N + R Cl Reflux 80ºC 24 h N+ N R Cl - + HX RT – 24 h _ _ _ (X = PF 6 , BF 4 ) N+ N ü Non-measurable vapour pressure Green solvent ü High ionic conductivity and thermal stability ü Ability to solubilize a large range of organic molecules and transition metal complexes R X-

Room Temperature Ionic Liquids ü Do not permeate through either organophilic or hydrophilic dense membranes ü Possibly an environmentally benign alternative to classical organic solvents v High viscosity and low heat transfer v Purification of ionic liquids

Experimental [bmim] [BF 4] A + CH 3 COOH H 2 O + p-Ts. OH 60°C B W E § Hydrophobic RTIL [bmim] [PF 6] at temperatures over 50°C - hydrolysis producing HF and PO 43 - § The selected “dried” [bmim] [BF 4] had viscosity 26 c. P at 60°C § Due to crystallization on the lid of the vessel, a 50% excess of (-)-Borneol was used

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 Retentate Thermostat Feed Permeate Reaction vessel Vacuum pump Cold trap Permeate Pervaporation experiment – standard laboratory pervaporation set-up with effective membrane area of 100 cm 2 ; downstream pressure p = 0. 06 mbar

Esterification at 60°C cat, kf kb

Model assumptions 1. Isothermal operation 2. Ideal mixing for all reactants in reactor 3. Negligible permeation of reactants through the membrane The consumption of acetic acid can be expressed by: (1) Moles of acetic acid consumed during esterification can be expressed as: (2)

Differential equations for modeling For the other components it can be derived: (-)-Borneol: (3) Water: (4) (-)-Bornyl acetate: (5) where R is the process variable: (6)

Volume change in the reactor Taking into consideration that the ionic liquid does not permeate through the PVA membrane, d. V/dt can be expressed by: (7) All differential Eqs. (2 -5, 7) were solved by the least square method using Scientist software.

Fitting of esterification reaction kf = (2. 72 ± 0. 13)× 10 -4 m 3 mol-1 h-1

Esterification coupled with pervaporation Jb = 8. 96× 10 -3 mol m-2 h-1

Drying of [bmim] [BF 4] by PV

Simulation of esterification coupled with pervaporation Parameters used for the simulation: . . . simulation: Jw = (-1. 19[W]2 + 2. 42 [W] ) mol m-2 h-1; Jb = 8. 96× 10 -3 mol m-2 h-1; . . K ; K = (0. 629 ± 0. 038); kf = (2. 74 ± 0. 13) × 10 - 4 m 3 mol-1 h-1; R = 48 m-1

Comparison of esterification with and without pervaporation

Effect of SM/V ratio on water concentration in the reactor

Effect of SM/V ratio on conversion to (-)-Bornyl acetate in the reactor

Conclusions • 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

Acknowledgement • This research was supported by Marie Curie Intra. European and Marie Curie Reintegration Fellowships within the 6 th European Community Framework Programme and by Purkyne Fellowship from Czech Academy of Science. • Thank you for your attention!