Extraction of Toluene from a Toluene/n-Heptane Mixture Using Protonated Imidazolium-Based Ionic Liquids

Abstract

The liquid–liquid equilibria (LLE) of the ternary system consisting of toluene, n-heptane, and ethylimidazolium bis(trifluoromethyl)sulfonylimide ([EtIM][NTf2]) were measured over the temperature range 298.2–313.2 K at ambient pressure. A binary mixture of [EtIM][NTf2] and methylimidazolium bis(trifluoromethyl)sulfonylimide ([MeIM][NTf2]) was used instead of [EtIM][NTf2] to investigate the effect of an additional ionic liquid on toluene separation from a toluene/n-heptane mixture. The LLE of a different ternary system of toluene, n-heptane, and [MeIM][NTf2] was also measured at 313.2 K and ambient pressure. Ionic liquids were not detected in the raffinate phase and thus no further separation unit for ionic liquids was required in the toluene separation process. The values of the distribution coefficient of toluene with the ionic liquids used in this study are higher than those with sulfolane at 313.2 K. This should provide a significant benefit because a higher distribution coefficient for toluene yields a more economic feed-to-solvent ratio in aromatic separations.