Vapor–liquid equilibria of {n-heptane + toluene + [emim][DCA]} system by headspace gas chromatography

Abstract

The potential use of ionic liquids (ILs) in the extraction of aromatics from aromatic/aliphatic mixtures has been widely evaluated in the last decade. In addition to the good results obtained in the extraction step, the non-volatile character of ILs could simplify the aromatic recovery unit. However, the scarce vapor–liquid equilibria (VLE) data for {aliphatic+aromatic+IL} systems demand additional experimental VLE data for such systems to correctly define the aromatic recovery from the extract stream. Only then, it will be possible to assess as a whole if the application of ILs as replacement to conventional organic solvents could represent a real improvement of the present aromatic extraction industrial methods. Thus, the aim of this work has been to measure the VLE for the {n-heptane+toluene+1-ethyl-3-methylimidazolium dicyanamide ([emim][DCA])} system. This mixture includes one of the most promising IL-based solvents reported previously for aromatic extraction. Static headspace gas chromatography (HS-GC) was employed to measure isothermal VLE at 323.2K, 343.2K, and 363.2K over the whole range of compositions within the rich-IL miscibility region. Also, the correlation of the VLE data to non-random two liquids (NRTL) thermodynamic model was successfully done. A high increase in the n-heptane relative volatility from toluene was achieved under the presence of [emim][DCA].