Selective absorption of gases by ionic liquids based on carboxylate anions or tris (pentafluoroethyl) trifluorophosphate anions
Different classes of ionic liquids have been selected for their ability to solubilize gases and more particularly carbon dioxide. The objective of this work is to define the ionic liquids which are most likely to be used as alternative absorbents in capture processes of gases, the main issue is to reduce the costs of production of the industrial processes. The systems used are the pure ionic liquids from the combination of imidazolium, phosphonium and pyrrolidinium cation with carboxylate or tris (pentafluoroethyl) trifluorophosphate anion and binary mixtures of ionic liquids with carboxylate anion + water. The absorption of different gases - carbon dioxide, nitrogen, nitrous oxide and ethane – in pure ionic liquids as well as in mixtures of ionic liquid + water was measured in a temperature range of between 303.15 and 353.15 K and pressures close to atmospheric. The selectivity of ionic liquids for the absorption of carbon dioxide from other gases could was determined. Characterization of gas absorption is a function of the studied system, since the interactions between gas and ionic liquid (or mixture ionic liquid + water) are of the physical type for some systems, while in other, the absorption is the result of both physical interaction and chemical reaction.