Separation of the isopropanol-water azeotropic mixture using ionic liquids

Vapor-liquid equilibrium (VLE) measurements of the isopropanol-water-ionic liquid ternary mixtures were performed using an ebulliometer at 101.3 kPa. The ionic liquids (ILs) synthesized and examined as entrainers for breaking the azeotrope of the isopropanol-water mixture are: 2-hydroxyethylammonium formate (2HEAF), 2-hydroxyethylammonium acetate (2HEAA) and 2-hydroxyethylammonium butyrate (2HEAB). Three initial IL (entrainer) concentrations in the feed solution were examined in the VLE experiments: ≈9%, ≈14.5% and ≈19.2% w/w. It is shown that the introduction of the entrainers to the isopropanol-water system results in an increase of the relative volatility leading to the successful elimination of the azeotropic point. The relative volatilities decrease with increasing the alkyl chain length of the anion of the IL, following the order: 2HEAB<2HEAA<2HEAF. Dynamic viscosities of the ionic liquids were measured in the temperature range from 293.15 to 363.15 K. Finally, thermodynamic modeling of the isopropanol-water-IL mixtures was performed with the UNIQUAC and NRTL models, and the results for both models were found to be in good agreement with the experimental data.