(Liquid + liquid) extraction of methanol from alkanes using dialkylphosphate-based ionic liquids as solvents

In this work, the feasibility of ionic liquids (ILs), 1,3-dimethylimidazolium dimethylphosphate ([MMIM][DMP]), 1-ethyl-3-methylimidazolium diethylphosphate ([EMIM][DEP]), and 1-butyl-3-methylimidazolium dibutylphosphate ([BMIM][DBP]), as solvents for the extraction of methanol from its mixtures with hexane and heptane was analyzed. The knowledge of (liquid + liquid) equilibria (LLE) of these mixtures is necessary for the design of the extraction separation process. Hence, the LLE data for the ternary systems, {methanol + hexane + ([MMIM][DMP], or [EMIM][DEP], or [BMIM][DBP])}, and {methanol + heptane + ([MMIM][DMP], or [EMIM][DEP], or [BMIM][DBP])}, were measured at T = 298.2 K and atmospheric pressure. The experimental results were correlated with the thermodynamic nonrandom two-liquid (NRTL) model. The solute distribution ratios of methanol and methanol/alkane selectivities, derived from the experimental LLE data, were calculated and analyzed to evaluate the capability of the studied ILs to accomplish the separation target. Meanwhile, these capabilities were also compared with that of other ILs obtained from the literature.