Vapor-liquid equilibria for n-heptane + (benzene, toluene, p-xylene, or ethylbenzene) + {[4empy][Tf2N] (0.3) + [emim][DCA] (0.7)} binary ionic liquid mixture

Abstract

Ionic liquids (ILs) have been extensively used as solvents in the liquid–liquid extraction of aromatics from aromatic/aliphatic mixtures. However, scarce studies have been done in order to experimentally evaluate the recovery of the hydrocarbons from the IL in extract-type streams. In this work, we have determined the vapor–liquid equilibria (VLE) for n-heptane + (benzene, toluene, p-xylene, or ethylbenzene) + {1-ethyl-4-methylpyridinium bis(trifluoromethylsulfonyl)imide ([4empy][Tf2N]) (0.3) + 1-ethyl-3-methylimidazolium dicyanamide ([emim][DCA]) (0.7)}. This IL mixture was selected as a result of its high extractive performance. The VLE have been measured using a headspace – gas chromatography (HS-GC) technique at several temperatures (323.2 K, 343.2 K, and 363.2 K) and over the whole composition range in the miscibility region of the systems. The Non-Random Two Liquids (NRTL) model has been applied to fit the VLE data. The n-heptane/aromatic relative volatilities have been calculated to assess the recovery of n-heptane from the four aromatics of the aromatic fraction and the IL-mixture. Results show that the IL mixture induces a high selective n-heptane/aromatic separation over the whole range of compositions in all systems and at all temperatures set in this work.