Influence of the nature of the ionic liquid on the selective transport of the substrates and products of transesterification reactions through supported liquid membranes based on ionic liquids
Advancing the chemical engineering fundamentals
Membranes and Membrane Science (T2-8P)
Keywords: supported liquid membranes, ionic liquids, selective transport, transesterification reactions, octanol-water partition coefficients
Influence of the nature of the ionic liquid on the selective transport of the substrates and products of transesterification reactions through supported liquid membranes based on ionic liquids
F. J. Hernández-Fernández*, A. P. de los Ríos, F. Tomás-Alonso, D. Gómez, 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: fjhernan@um.es
Supported liquid membranes (SLMs) is recognized as one of the most promising membrane-based techniques [1]. Although SLMs have been widely studied for the separation and concentration of a variety of compounds and present many potencial advantages over other separation methods, there have been very few large scale applications of SLM due to insufficient membrane stability, which can be due to the loss of the solvent from the membrane. One potencial solution of this problem is employing ionic liquids (ILs) as a liquid membrane phase. Ionic liquids are organic salts that are liquid close to room temperature. They normally consist of an organic cation, being the most commonly used dialkylimidazolium and tetraalkylammomiun salts, and a polyatomic inorganic anion (e.g. BF4-, PF6-) [2]. The use of ILs as liquid membrane phase results in the stabilization of the SLM because ionic liquid have negligible vapour pressure and their solubility in the surrounding phases can be minimized by adequate selection of the cation and the anion [3].
The present work seeks to broaden the field of application of supported ionic liquid membranes to the selective separation of the substrates and products of a transesterification reaction, for possible use in future integrated reaction/separation processes. This work analysed the transport of vinyl butyrate, 1-butanol, butyl butyrate and butyric acid, substrates and products of a transesterification reaction, through ILs based on the 1-n-alkyl-3-methylimidazolium cation (n-butyl, n-octyl) and the hexafluorophosphate, tetrafluoroborate or bis{(trifluoromethyl)sulfonyl}imide anions immobilized in Nylon membranes, evaluating the influence of the hydrophobic/hydrofilic character of the ionic liquids on the behaviour of the resulting supported liquid membranes. The experimental device consisted in a diffusion cell made of two independent compartments of equal volumes separated by the SLM. Control experiments were performed without ionic liquids, showing no selectivity for the transport. However, significant permeability difference between the organic compounds was observed when ionic liquids were supported in the Nylon membranes.
In order to analyzed the influence of the hydrophobic/hydrofilic character of the ionic liquids on the efficiency of separation, this parameter has been measured as the partition coefficients of each ionic liquid between octanol and water (Kow). It has been observed that an increase in the hydrofilic character of the ionic liquid is in agreement with an increase in the efficiency of separation.
Acknowledgment:
This work was partially supported by the CICYT CTQ2005-09238/PPQ grant.
References:
[1] J. T. F. Keurentjes, L. J. W. M. Nabuurs, E. A. Vegter. J. Memb. Sci. 113 (1996) 351.
[2] J. F. Brennecke, E. J. Maginn. AIChE Journal 47 (2001) 2384.
[3] L. C. Branco, J. G. Grespo, C. A. M. Afonso. Chem. Eur. J. 8 (2002) 3865.
Presented Tuesday 18, 13:30 to 15:00, in session Membranes and Membrane Science (T2-8P).
