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

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.

► 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.