Vapor–Liquid Equilibrium for Ethyl Acetate + Acetonitrile with Acetate-Based Ionic Liquids as Entrainers at 101.3 kPa and Analysis of the Separation Mechanism

Isobaric vapor–liquid equilibrium (VLE) data for the ternary system of ethyl acetate + acetonitrile + acetate-based ionic liquids (ILs) were obtained with a modified Othmer still at 101.3 kPa, and the used ILs were 1-butyl-3-methylimidazolium acetate ([BMIM][Ac]) and 1-ethyl-3-methylimidazolium acetate ([EMIM][Ac]). The VLE data were correlated with the nonrandom two-liquid model and fitted well, indicating that the minimum mole fractions of [BMIM][Ac] and [EMIM][Ac] to eliminate azeotrope were 0.028 and 0.067, respectively. Both [BMIM][Ac] and [EMIM][Ac] led to a salting-out effect on ethyl acetate, and a higher concentration of ILs signified a stronger salt effect. In addition, interactions between ILs and solvents were estimated, and the polarity was analyzed with the σ-profiles, revealing the effect of ILs and the separation mechanism of the ternary system. The results indicated that both [BMIM][Ac] and [EMIM][Ac] could be qualified as solvents to separate ethyl acetate and acetonitrile. Based on the experimental data measured on the equilibrium scale and the separation mechanism calculated at the molecular scale, this work provides a useful strategy for studying the application of IL in extractive distillation in the future.