Extraction of benzene, ethylbenzene, and xylenes from n-heptane using binary mixtures of [4empy][Tf2N] and [emim][DCA] ionic liquids

•Extraction of aromatics from n-heptane employing mixed ILs was studied.•Extractive properties of mixed ILs were between those of pure ILs.•The highest extractive properties were achieved in the separation of benzene.•LLE data of pseudoternary systems were measured and fitted to the NRTL model.•The [4empy][Tf2N] + [emim][DCA] mixture was revealed as a replacement of sulfolane.

Benzene, toluene, ethylbenzene, and xylenes (BTEX) are mainly obtained by liquid–liquid extraction from pyrolisis and reformer gasolines using sulfolane as solvent. The use of ionic liquids (ILs) as replacements of sulfolane has been extensively studied, because an industrial process of aromatic extraction using ILs could have fewer process steps and lower operating costs as a result of the exceptional properties of ILs. Nevertheless, pure ILs studied so far have not simultaneously shown physical and extractive properties comparable to those of sulfolane. In our recent work, we studied the use of 1-ethyl-4-methylpyridinium bis(trifluoromethylsulfonyl)imide ([4empy][Tf2N]) and 1-ethyl-3-methylimidazolium dicyanamide ([emim][DCA]) binary IL mixtures as toluene extraction solvent from its mixtures with n-heptane, 2,3-dimethylpentane, and cyclohexane. The {[4empy][Tf2N] + [emim][DCA]} mixture showed better extractive properties than those of sulfolane, whereas their densities and viscosities were similar to the sulfolane values. In this work, we have studied the performance of {[4empy][Tf2N] + [emim][DCA]} IL mixtures in the liquid–liquid extraction of benzene, ethylbenzene, o-xylene, m-xylene, and p-xylene from n-heptane at 313.2 K. To evaluate the applicability of the IL mixtures as extraction solvent of BTEX, liquid–liquid equilibria (LLE) experiments have also been performed using sulfolane under the same conditions. A {[4empy][Tf2N] + [emim][DCA]} mixture with a [4empy][Tf2N] mole fraction of 0.3 has been revealed as a potential replacement of sulfolane in the liquid–liquid extraction of BTEX, according to its extractive and physical properties.