Liquid-liquid equilibrium measurements and interaction exploration for separation of isobutyl alcohol + isobutyl acetate by imidazolium-based ionic liquids with different anions

•The LLE data for isobutyl acetate + isobutyl alcohol + ILs were measured and correlated by the NRTL model.•The distribution coefficient and selectivity were calculated.•The σ-profiles and interaction energies were calculated to explore interaction ILs with (isobutyl alcohol/isobutyl acetate).•[Bmim][H2PO4] is suitable as extractant to separate the azeotropic mixture IBA and IBAC. For separation of the azeotropic mixture isobutyl alcohol and isobutyl acetate, liquid-liquid extraction was adopted in this work and three imidazolium-based ionic liquids with different anions 1-butyl-3-methylimidazolium dihydrogen phosphate ([Bmim][H2PO4]), 1-butyl-3-methylimidazolium hydrogen sulfate ([Bmim][HSO4]) and 1-butyl-3-methylimidazolium methyl sulfate ([Bmim][MeSO4]) were chosen as extractants. The liquid – liquid equilibrium data (LLE) for isobutyl alcohol + isobutyl acetate + ([Bmim][H2PO4]/[Bmim][HSO4]/[Bmim][MeSO4]) were determined at 298.15 K and 101.3 kPa. The distribution coefficient and selectivity were calculated to evaluate extraction capability of the selected extractants. Furthermore, the σ-profiles and interaction energies based on conductor-like screening segment activity coefficient model (COSMO-SAC) were calculated to provide theoretical insight to interactions among the components. Also, the measured LLE data was correlated by the NRTL model and binary interaction parameters were regressed which is helpful for the separation process design and optimization.