Separation of hex-1-ene/hexane and cyclohexene/cyclohexane compounds with [EMIM]-based ionic liquids

Abstract

In this work we studied the applicability of three imidazolium-based ionic liquids (ILs) with different anions in the separation of hex-1-ene/hexane and cyclohexene/cyclohexane compounds. Experimental data for liquid–liquid equilibrium (LLE) were obtained for various binary and ternary mixtures of {IL (1) + hex-1-ene (2) + hexane (3)} or {IL (1) + cyclohexene (2) + cyclohexane (3)} at T = 298.15 K and ambient pressure. Three ILs have been studied: 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)-imide, [EMIM][NTf2], 1-ethyl-3-methylimidazolium dicyanamide, [EMIM][DCA] and 1-ethyl-3-methylimidazolium tricyanomethanide, [EMIM][TCM]. ILs were chosen after a literature analysis and measurements of activity coefficient at infinite dilution in many ILs. Chosen ILs showed excellent results in terms of selectivity and solute distribution ratio. The chromatography analysis revealed that the ILs used as an entrainers were not present in the hydrocarbon-rich layer. This is convenient for planned technology, because eliminates the step needed for the separation of the solvent. A comparative study of the separation effectiveness of the [EMIM][TCM] in comparison with two other reported ILs was chosen as the better solvent for the intended two separation processes. The non-random two liquid NRTL model was used successfully to correlate the experimental tie-lines and to calculate the phase composition error in mole fraction in the ternary systems.