Vapor–Liquid Equilibrium Experiment and Thermodynamic Correlation of n-Propanol + n-Propyl Acetate + 1-Ethyl-3-methylimidazolium Acetate and 1-Hexyl-3-methylimidazolium Acetate

In the esterification reaction of n-propanol and acetic acid to produce n-propyl acetate, the presence of a mixture of n-propanol and n-propyl acetate is inevitable. However, the system of n-propanol and n-propyl acetate has an azeotropic point, which makes it impossible for conventional distillation to separate the two substances completely. Therefore, 1-ethyl-3-methylimidazolium acetate ([EMIM][OAC]) and 1-hexyl-3-methylimidazolium acetate ([HMIM][OAC]) were selected as entrainers to conduct the vapor–liquid equilibrium experiment of n-propanol + n-propyl acetate + [EMIM][OAC] and n-propanol + n-propyl acetate + [HMIM][OAC] at atmospheric pressure in this study. The experimental data were regressed by the NRTL model and UNIFAC-Lei model. NRTL model was in better agreement with the experimental data. The results showed that both [EMIM][OAC] and [HMIM][OAC] could separate the n-propanol + n-propyl acetate system, and [EMIM][OAC] showed the enormous separation potential of ionic liquids based on [OAC]− as anions for the azeotropic system.