Study of the suitability of two ammonium-based ionic liquids for the extraction of benzene from its mixtures with aliphatic hydrocarbons

Abstract

The ammonium-based ionic liquids butyltrimethylammonium bis(trifluoromethylsulfonyl)imide, [N4111][NTf2] and tributylmethylammonium bis(trifluoromethylsulfonyl)imide, [N4441][NTf2] have been studied as separation agents on the extraction of benzene from its mixtures with the long chain aliphatic hydrocarbons octane, decane and dodecane. The liquid–liquid equilibria of the ternary systems {octane (1) + benzene (2) + [N4111][NTf2] (3)}, {decane (1) + benzene (2) + [N4111][NTf2] (3)}, {dodecane (1) + benzene (2) + [N4111][NTf2] (3)} and {dodecane (1) + benzene (2) + [N4441][NTf2] (3)} at T = 298.15 K and {octane (1) + benzene (2) + [N4441][NTf2] (3)} at T = (298.15, 308.15 and 318.15) K and atmospheric pressure were determined. From the experimental results, an analysis of the influence of the cation of the ammonium-based ionic liquids and the alkyl chain length of the aliphatic hydrocarbons was performed; together with a study of the effect of the temperature on the liquid-liquid extraction of benzene. The extraction effectiveness was evaluated by the calculation of solute distribution ratio and selectivity derived from the tie-lines compositions. Besides, a comparison of the obtained results with those found in literature for systems with sulfolane, which is the most industrially used solvent, was performed. Finally, the experimental tie-lines were correlated using the NRTL thermodynamic model.