Effect and Mechanism of 1-Hexyl-3-methylimidazolium-Based Ionic Liquids on the Isobaric Vapor–Liquid Equilibria of Methanol + Acetonitrile at 101.3 kPa

This work studied the separation effect of 1-hexyl-3-methylimidazolium-based ionic liquids (1-hexyl-3-methylimidazolium tetrafluoroborate [HMIM][BF 4 ] and 1-hexyl-3-methylimidazolium trifluoromethanesulfonate [HMIM][OTF]) to separate a methanol and acetonitrile azeotropic system. The isobaric vapor–liquid equilibrium data obtained for the ternary systems {methanol + acetonitrile + ([HMIM][BF 4 ] or [HMIM][OTF])} were measured at 101.3 kPa. Based on the nonrandom two-liquid model, the minimum mole fractions of [HMIM][BF 4 ] and [HMIM][OTF] required to eliminate the azeotrope point of the methanol + acetonitrile mixtures were 0.047 and 0.042, respectively. Through the analysis of the σ-profiles and separation ability, [HMIM][OTF] was a suitable entrainer to separate the methanol–acetonitrile azeotrope.