Separation of acetonitrile + isopropanol azeotropic mixture using ionic liquids with acetate anion as entrainers

Three ionic liquids, including 1-ethyl-3-methylimidazolium acetate ([EMIM][Ac]), 1-butyl -3-methylimidazolium acetate ([BMIM][Ac]) and 1-hexyl -3-methylimidazolium acetate ([HMIM][Ac]), were selected as entrainers to separate the azeotropic system of acetonitrile + isopropanol. Isobaric vapor liquid equilibrium data of the acetonitrile + isopropanol + ILs ternary systems were determined at 101.3 kPa. The separation performance of the three ionic liquids were analyzed and compared. The nonrandom two-liquid (NRTL) model was used to correlate the experimental data. The addition of [EMIM][Ac] and [BMIM][Ac] could increase the relative volatility of acetonitrile to isopropanol at acetonitrile-rich region, whereas [HMIM][Ac] produced an salting-out effect on acetonitrile at full-concentration region and the effect was more obvious with the increase of its content. All three ILs could break the azeotropic point as their content reach a certain value. The NRTL model was proved to be applicable to the acetonitrile and isopropanol systems containing the three ILs. The separation performance of the three ionic liquids is [HMIM][Ac]>[BMIM][Ac]>[EMIM][Ac].