Vapor–Liquid Phase Equilibrium for Separation of Isopropanol from Its Aqueous Solution by Choline Chloride-Based Deep Eutectic Solvent Selected by COSMO-SAC Model

Abstract

To separate isopropanol from its aqueous solution by distillation, the deep eutectic solvents (DESs) with choline chloride, which were screened using the COSMO-SAC mode, were applied to eliminate the azeotropic point. The charge density distribution over the molecular surface was calculated for isopropanol, water, and DESs to analyze the interactions between different species. Based on the screening results, a DES consisting of choline chloride and triethylene glycol in a molar ratio of 1:3 was selected. To validate the selected DES for the separation of isopropanol from its aqueous solution, the isobaric vapor–liquid equilibrium (VLE) data for the system of isopropanol + water + DES were measured at a pressure of 101.3 kPa. According to the measured VLE data, the azeotropic point of isopropanol and water can be eliminated by the DES at a concentration of 10 wt %. Meanwhile, the thermodynamic consistency of the VLE data was checked by the van Ness test. The non-random two-liquid model was employed to correlate the VLE data, which were in agreement with the measured VLE data.