Liquid–liquid equilibria for ternary systems ethanol + heptane + phosphoric-based ionic liquids

This work demonstrates the capabilities of three phosphoric-based ionic liquids (ILs) as solvents for the extraction of ethanol from its mixture with heptane. The knowledge of liquid–liquid equilibria (LLE) of this mixture is essential for the design of the extraction separation process. For this reason, the experimental LLE data were measured for the ternary systems, {ethanol   +   heptane   +   1,3-dimethylimidazolium dimethylphosphate ([MMIM][DMP]), or 1-ethyl-3-methylimidazolium diethylphosphate ([EMIM][DEP]), or 1-butyl-3-methylimidazolium dibutylphosphate ([BMIM][DBP])}, at T   =   298.2   K and atmospheric pressure. The thermodynamic nonrandom two-liquid (NRTL) model was used to correlate the experimental results for the studied ternary systems. The extraction capabilities for the studied ILs were evaluated by solute distribution ratios of ethanol and ethanol/heptane selectivities. Moreover, this extraction capability was also compared with other ILs obtained from the literature. The experimental results show that the studied ILs can be suitable to act as solvents for the separation of the ethanol and heptane in the extraction process. The extraction capabilities for the studied ILs decrease in the following order [MMIM][DMP]   >   [EMIM][DEP]   >   [BMIM][DBP].