Application of [HMim][NTf2], [HMim][TfO] and [BMim][TfO] ionic liquids on the extraction of toluene from alkanes: Effect of the anion and the alkyl chain length of the cation on the LLE

Highlights: ► Several ionic liquids were studied as solvent to extract toluene from heptane and cyclohexane. ► (Liquid + liquid) equilibrium data were measured at 298.15 K and atmospheric pressure. ► Selectivity and solute distribution ratio were calculated and compared with those found in literature for sulfolane. ► Experimental data were correlated using NRTL and UNIQUAC thermodynamic models. - Abstract: In this paper, the separation of toluene from the aliphatic hydrocarbons heptane and cyclohexane employing the ionic liquids 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [HMim][NTf2], 1-hexyl-3-methylimidazolium trifluoromethanesulfonate, [HMim][TfO] and 1-butyl-3-methylimidazolium trifluoromethanesulfonate, [BMim][TfO], as solvents was studied and discussed. Liquid–liquid equilibrium data for the ternary systems {heptane, or cyclohexane + toluene + [HMim][NTf2], or [HMim][TfO], or [BMim][TfO]} and {heptane + cyclohexane + [HMim][NTf2], or [HMim][TfO], or [BMim][TfO]} were measured at T = 298.15 K and atmospheric pressure. The degree of consistency of the tie-lines was tested using the Othmer–Tobias equation. The solute distribution ratio and selectivity, derived from the experimental tie-lines, were used to determine if these ionic liquids can be used as potential solvents on the extraction of toluene from aliphatic hydrocarbons; a comparison with literature data where sulfolane is used as solvent was also included. Finally, the experimental data were correlated with the NRTL and UNIQUAC thermodynamic models.