Entrainer Screening, Vapor–Liquid Equilibrium Measurement, and Extractive Distillation Simulation for the Ethyl Propionate–Ethanol Azeotropic System

Abstract The separation of ethyl propionate (EtPr) from the EtPr-ethanol (EtOH) azeotropic system is a challenging industrial problem. Herein, 252 ionic liquids (ILs) were screened via COSMO-RS theory, and tributylmethylammonium acetate ([N4441][Ac]) was selected as the optimal extractive distillation entrainer by evaluating selectivity and infinite-dilution solvent capacity. Vapor–liquid equilibrium (VLE) data of the EtPr (1) + EtOH (2) + [N4441][Ac] (3) system were measured at 101.3 kPa. The added [N4441][Ac] effectively improved the relative volatility of EtPr and completely eliminated the azeotrope at an IL mole fraction of 8%. The NRTL model provided accurate data correlation with reliable thermodynamic consistency. An optimized extractive distillation process was established via Aspen Plus V11 to obtain high-purity EtPr and EtOH. Economic analysis shows that the proposed process reduces total annual cost (TAC) by 18.75% and 38.83% compared with ethylene glycol-based extractive distillation and vacuum distillation, respectively.