Ionic liquids as entrainers for the separation of azeotropic mixtures: Experimental measurements and COSMO-RS predictions

This work focuses on the evaluation of protic ionic liquids (PILs), prepared by direct neutralization of ethanolamine with different carboxylic acids, for being used as entrainers in the separation of ethanol-water azeotropic mixture. Isobaric vapor-liquid equilibria measurements, for ethanol-water mixtures with 2-hydroxyethylamonium formate and 2-hydroxyethylamonium butyrate, at initial concentrations of 5%, 10% and 15% mass fraction, have been carried out at 101.3 kPa. The results reveal that ILs increase the relative volatility of the ethanol-water mixture shifting the azeotrope towards higher ethanol concentrations, ultimately leading to complete azeotrope elimination. Intermolecular interactions between components of the binary alcohol-water and the ternary alcohol-water-IL mixtures were theoretically studied with the COSMO-RS model, using two different approaches to treat the IL: firstly, as a single compound and secondly, as a separate cation and anion. It is shown that COSMO-RS is able to qualitatively predict the experimental data, although significant quantitative deviations are observed. (C) 2020 Elsevier Ltd. All rights reserved.