Kinetic resolution of rac-1-phenylethanol in a stirred tank bioreactor in ionic liquid/supercritical carbon dioxide biphasic systems
Special Symposium - EPIC-1: European Process Intensification Conference - 1
EPIC-1: Poster Session (EPIC - Poster) - P1
Keywords: Kinetic resolution, bioreactor, ionic liquid, supercritical carbon dioxide, liquid-liquid equilibria
Kinetic resolution of rac-1-phenylethanol in a stirred tank bioreactor in ionic liquid/supercritical carbon dioxide biphasic systems
A.P. de los Ríos, F.J. Hernández-Fernández, D. Gómez, F. Tomás-Alonso, M. Rubio and G. Víllora*
Department of Chemical Engineering , Faculty of Chemistry, University of Murcia, P.O. Box 4021, Campus de Espinardo, E-30100, Murcia, Spain.
E-mail: gvillora@um.es
There is a continuing interest in developing new concepts for biphasic or phase-separable catalysis where a catalyst is immobilized in one liquid phase and the reactants and/or products reside largely in another liquid phase. One example is the combination of ionic liquids (ILs) and supercritical carbon dioxide (scCO2). The different miscibilities of scCO2 and ILs lead to two-phase systems that have found application in several areas [1,2]. The success of this two-phase system is based on solubility of scCO2 in the IL but insolubility of the IL in the scCO2.
In this work, the kinetic resolution of rac-1-phenylethanol in a stirred tank bioreactor in ionic liquid/supercritical carbon dioxide biphasic systems at 70ºC and 100 bar was studied. In these systems, a commercially immobilized Candida antarctica lipase B (Novozyme 435) was coated with two different ionic liquids: (i) 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim+][PF6-]) and (ii) 1-butyl-3–methylimidazolium tetrafluoroborate ([bmim+][BF4-]) and then introduced into the tank. The reactor was filled of CO2 and the reaction was started by introducing the substrates. The efficiency of the catalytic action was analyzed by means of three parameters: the synthetic rate, the selectivity (ratio between the synthetic rate and the hydrolytic rate) and the enantioselectivity. When room temperature ionic liquid/supercritical carbon dioxide biphasic systems were used the enantioselectivity of the process was > 99.9% and the selectivity about 90%. However, the synthetic activity decreased compared with supercritical carbon dioxide assayed in absence of ILs, probably due to the mass-transfer limitations across the IL-layer around the biocatalyst, being much smaller for the water-miscible IL, [bmim+][BF4-].
In order to get a better understanding of the mass transfer phenomena involves in this process,
the solubility, the diffusion rate and the liquid-liquid equilibrium data of the substrates and products (rac-1-phenylethanol, rac-1-phenylethyl propionate, propionic acid, vinyl propionate) were studied. Liquid-liquid equilibrium data has been obtained for mixtures of IL+hexane+solute, where hexane has been used as reference solvent because its solvent capability may be comparable to that in supercritical carbon dioxide in mild operating conditions. This study also could allows us to design integrated reaction-separation processes using ionic liquids as reaction media and supercritical carbon dioxide as extractor solvent.
Acknowledgements:
This work was partially supported by the CICYT CTQ2005-09238/PPQ grant.
References
[1,] F.J. Hernández, A.P. de los Ríos, D. Gómez, M. Rubio, G. Víllora. Appl. Catal. B: Environmental 67 (2006), 121.
[2] L.A. Blanchard, J.F. Brennecke. Ind. Eng. Chem. Res. 40 (2001) 287.
Presented Wednesday 19, 13:30 to 14:40, in session EPIC-1 Poster Session (EPIC - Poster) - P1.
