Ternary LLE measurements for the separation of hex-1-ene/hexane and cyclohexene/cyclohexane compounds with [DCA]-based ionic liquids

Abstract

The objective of this work was to explore the feasibility of separation of hex-1-ene from hexane and cyclohexene from cyclohexane with new ionic liquids (ILs) with [DCA]_ anion. With this aim, the liquid–liquid phase equilibrium (LLE) for three ternary systems of {IL (1) + hex-1-ene (2) + hexane (3)} and two {IL (1) + cyclohexene (2) + cyclohexane (3)} at T = 298.15 K were determined at ambient pressure. Three new ILs have been presented and used in LLE measurements: 3-(2-methoxyethyl)-1-methylimidazolium dicyanamide, [(C2OCH3)MIM][DCA], 1-(4-methoxy-4-oxobutyl)-3-methylimidazolium dicyanamide, [(C3COOMe)MIM][DCA] and choline dicyanamide, [Chol][DCA]. The anion of the ILs was chosen after a literature analysis and measurements of activity coefficient at infinite dilution in many ILs. Chosen ILs revealed large selectivity and very low solute distribution ratio. The results of the chromatography analysis indicated that the ILs used as an entrainers were not detected in the hydrocarbon-rich layer, which is convenient, because eliminates the step needed for the separation of the solvent. The well known NRTL activity coefficient model was used to correlate the LLE data.