Polymer-based Ionic Liquid Gel Membranes for Gas and Vapour Separation

In the last decades membrane operations have gained an increasingly important role in industrial gas separation processes . Polymeric membranes are most widely used for this application. They offer a broad spectrum of properties, which can be further tailored by blending with other polymers or by low molar mass additives such as room temperature ionic liquids (RTILs). Since gas transport in polymeric membranes is based on the solution-diffusion mechanism, addition of RTILs significantly affects the transport properties in polymers, either by changing the gas affinity or the gas mobility. In this paper we present a detailed study of the thermal, mechanical and transport properties of stable polymer gel membranes based on various RTILs in semi-crystalline polymers such as poly(vinylidene fluoride-co-hexafluoropropylene) (p(VDF-HFP)) and poly(ether-b-amide) . By a proper choice of the materials the mechanical properties and the permeability can be varied over several orders of magnitude and their correlation can be used to identify the transition from diffusion-controlled to solubility-controlled transport (Fig. 1). The presence of the RTIL strongly increases the CO2 selectivity of the membranes, especially with respect to gases with lower solubility such as hydrogen. Vapour transport in these membranes is strongly affected by polar interactions such as hydrogen bonding, causing a fundamental difference between the behaviour of alkanes and alcohols. An overview of the most interesting results will be given. 1 P. Bernardo, E. Drioli, G. Golemme, Ind. Eng. Chem. Res. 2009, 48, 4638. 2 J.C. Jansen, K. Friess, G. Clarizia, J. Schauer, P. Izák, Macromolecules. 2011, 44, 39. 3 P. Bernardo, J.C. Jansen, F. Bazzarelli, F. Tasselli, A. Fuoco, K. Friess, P. Izák, V. Jarmarová, M. Ka?írková, G. Clarizia, Sep. Purif. Technol. 2012, 97, 73. 4 K. Friess, J.C. Jansen, F. Bazzarelli, P. Izák, V. Jarmarová, M. Ka?írková, J. Schauer, G. Clarizia, P. Bernardo, J. Membr. Sci. 2012, 415-416, 801.