Ternary liquid–liquid equilibrium of an azeotropic mixture (hexane + methanol) with different imidazolium-based ionic liquids at T = 298.15 K and 101.325 kPa

Abstract The recovery and purification of methanol from its mixtures is of great importance; to this end, liquid-liquid extraction is an effective method for the separation of azeotropes. In this work, three imidazolium-based ionic liquids were used to separate a hexane-methanol azeotropic mixture, and the ternary liquid-liquid equilibria (LLE) data for the systems of hexane + methanol + [MIM][HSO 4 ] (1-methylmidazole hydrogen sulfate), [BMIM][HSO 4 ] (1-Butyl-3-methylimidazolium hydrogen sulfate), [BMIM][OTf] (1-Butyl-3-methylimidazolium trifluoromethansulfonate) were measured at 298.15 K and atmospheric pressure. The separation factor and distribution coefficient were calculated from the experimental LLE data to evaluate the separation performance. The influence of the anions and mono-/di-substituted hydrocarbon chains on the imidazolium cation ring of the LLE was investigated. The experimental LLE data were successfully correlated by non-random two liquid (NRTL) and universal quasi-chemical (UNIQUAC) models, and the binary interaction parameters were obtained.