Phosphoric-based ionic liquids as solvents to separate the azeotropic mixture of ethanol and hexane

Abstract

Ethanol and hexane mixtures are present in industrial processes producing oxygenated additives for unleaded gasoline. The separation of ethanol and hexane is important but challenging due to the formation of an azeotropic mixture. This research focuses on the study of phosphoric-based ionic liquids (ILs) as green solvents for the separation of ethanol from hexane in a liquid extraction process. The knowledge of the (liquid+liquid) equilibrium (LLE) of this mixture is essential for the design of the extraction separation technique. Hence, the experimental determination of the LLE data for the ternary system {ethanol+hexane+1,3-dimethylimidazolium dimethylphosphate ([MMIM][DMP])}, {ethanol+hexane+1-ethyl-3-methylimidazolium diethylphosphate ([EMIM][DEP])} and {ethanol+hexane+1-butyl-3-methylimidazolium dibutylphosphate ([BMIM][DBP])} at T=303.2K and atmospheric pressure was carried out. The reliability of the experimental LLE data was confirmed by applying the Othmer–Tobias and Hand equations, and the NRTL model was used to correlate the experimental results for the studied ternary system. The solute distribution ratio and selectivity, derived from the experimental LLE data, were calculated and analyzed evaluate the capacity of the investigated ILs as solvents in liquid extraction process. This capacity was also compared with that of other ILs. The experimental results show that the studied ILs can be suitable solvents in a (liquid+liquid) extraction for the separation of azeotropic mixtures of ethanol and hexane.