Highly efficient metal-free membranes for the separation of acetylene/olefin mixtures: Pyrrolidinium-based ionic liquids as acetylene transport carriers

Pyrrolidinium-based ionic liquids with a basic anion were shown to be highly effective acetylene transport carriers for the selective separation of acetylene in ethylene through membranes. The selectivity of acetylene over ethylene varied significantly depending on the type of the anion of the pyrrolidinium-based ionic liquids. The highest selectivity of 23 was attained when N,N-dimethylpyrrolidinium methylphosphite ([DMPyrr][MeHPO3]) was used as the transport carrier. Computational calculation and 1H NMR results on the interactions of acetylene and ethylene with [DMPyrr][MeHPO3] clearly indicate that the higher selectivity of acetylene over ethylene is originated from the specific acid–base interaction between methylphosphite anion, [MeHPO3]− and the acidic hydrogen atom(s) of acetylene.