Vapor–Liquid Equilibrium Experiment and Thermodynamic Correlation of Methyl Ethyl Carbonate + Ethanol + 1-Hexyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)imide and 1-Ethyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)imide at 101.3 kPa

Methyl ethyl carbonate (EMC) is an essential solvent in the production process of lithium batteries, which is in high market demand. However, it is costly and lacks purity. Preparing EMC with ethanol and dimethyl carbonate is environmentally friendly and efficient. Still, an azeotropic mixture of EMC and ethanol is formed during preparation, making it impossible for conventional distillation to separate these two substances. Therefore, this work adopts extraction distillation to separate the EMC–ethanol azeotropic system, selecting two ionic liquids (ILs), 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([HMIM][NTf2]) and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][NTf2]), as entrainers. The vapor–liquid equilibrium (VLE) experiment of the EMC (1) + ethanol (2) + ILs (3) ternary system was conducted under atmospheric pressure (101.3 kPa). The experimental results indicate that both ILs can eliminate azeotropic points and the separation ability of [HMIM][NTf2] is slightly stronger than that of [EMIM][NTf2]. The NRTL model was used to fit the experimental data, with ARDs of 4.17 and 4.40%, respectively, proving that the model is suitable for the system.