Gas Permeation Properties of Fluorinated Ionic Liquids

Despite the increasing amount of research in the ionic liquids field, there are still quite unexplored themes. That is the case of the fluorinated ionic liquids (FILs) family, here defined as ionic liquids with fluorine tags longer than four carbon atoms. In this work, gas permeation properties of two fluorinated ionic liquids, tetrabutylammonium heptadecafluorooctanesulfonate and 1-ethyl-3-methylpyridinium perfluorobutanesulfonate, were studied. For that purpose, supported liquid membranes of the fluorinated ionic liquids were prepared using a polymeric porous membrane as supporting material, and their gas permeation properties for 10 different gases at 294 K were measured using a time-lag apparatus. The results show that the gas solubility of these FILs is of the same order of magnitude as gas solubilities for previously tested fluorinated ionic liquids and that solute size plays a more important role on gas diffusivity than viscosity. The perfluorocarbons and carbon dioxide separation performances were evaluated, and the results show that 1-ethyl-3-methylpyridinium perfluorobutanesulfonate is a better candidate than tetrabutylammonium heptadecafluorooctanesulfonate for the gas separation processes tested in this work.