Vapor–Liquid Equilibrium for Acetonitrile + Ethanol with Imidazole-Based Ionic Liquids as Entrainers at 101.3 kPa

Vapor–liquid equilibrium (VLE) data for the ternary system of acetonitrile + ethanol + ionic liquids (ILs) were obtained at 101.3 kPa, and used ILs were 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM][NTf2]), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][NTf2]), and 1-butyl-3-methylimidazolium diethylphosphate ([BMIM][DEP]). The nonrandom two-liquid (NRTL) model was used to correlate the VLE data and fitted well, indicating that the minimum mole fractions of [BMIM][NTf2], [EMIM][NTf2], and [BMIM][DEP] to eliminate the azeotrope was 0.053, 0.063, and 0.065, respectively. These ILs led to an outstanding "salting-in" effect on ethanol, and the salting effect on acetonitrile was inapparent. Higher concentrations of ILs signified a stronger salt effect as well as higher equilibrium temperatures. The results indicated that [BMIM][NTf2], [EMIM][NTf2], and [BMIM][DEP] could be used as good candidate entrainers to separate acetonitrile and ethanol in extractive distillation.