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

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.