Separation of toluene from n-heptane using monocationic and dicationic ionic liquids

Liquid–liquid equilibrium data for the system consisting of toluene, n-heptane, and monocationic and dicationic ionic liquids were obtained at 303.15 K and atmospheric pressure. Monocationic ionic liquids 1-butyl-3-methylimidazolium hydrogen sulphate ([BMIM][HSO4]) and 3-methylimidazolium hydrogen sulphate ([HMIM][HSO4]) were used. Dicationic ionic liquids bis-(3-methyl-1-imidazole)-propylene hydrogen sulphate ([C3(MIM)2][(HSO4)2]) and bis-(3-methyl-1-imidazole)-hexylene hydrogen sulphate ([C6(MIM)2][(HSO4)2]) were used. The values of the partition coefficient and the selectivity were evaluated. The experimental data obtained were correlated using the non random two liquid (NRTL) model. The relatively high value of selectivity, in comparison with the conventional solvent sulpholane, suggests that the studied monocationic and dicationic ionic liquids can be used as alternative solvents for the separation of aromatics from aliphatics.

► Extraction of toluene from heptane using ionic liquids (ILs) was studied.
► ILs [HMIM]HSO4, [BMIM]HSO4, [C3(MIM)2][(HSO4)2] and [C6(MIM)2][(HSO4)2] were used.
► Experimental liquid–liquid equilibrium data were obtained at 303.15 K.
► The toluene/heptane selectivity values were higher with ILs than with sulpholane.
► The experimental data were well correlated with the NRTL model.