Dearomatization of pyrolysis gasolines from mild and severe cracking by liquid–liquid extraction using a binary mixture of [4empy][Tf2N] and [emim][DCA] ionic liquids

Abstract

In Europe and Japan, benzene, toluene, and xylenes (BTX) are usually obtained by liquid–liquid extraction from pyrolysis gasolines using organic solvents such as sulfolane. In the last few years, ionic liquids (ILs) have been studied as potential substitutes of conventional solvents in the extraction of BTX from alkanes. In this paper, we have studied the dearomatization of pyrolysis gasolines obtained by mild and severe cracking using the binary IL mixture composed of the 1-ethyl-4-methylpyridinium bis(trifluoromethylsulfonyl)imide ([4empy][Tf2N]) and the 1-ethyl-3-methylimidazolium dicyanamide ([emim][DCA]) and also employing sulfolane to compare the performance of both extraction solvents. To choose the most appropriate conditions of temperature and solvent to feed ratio to perform the extraction of BTX from pyrolysis gasolines, several extractive properties have been estimated from the experimental results employing the IL mixture and sulfolane. Simulations of countercurrent extraction columns in the dearomatization of both pyrolysis gasolines have also been made using the Kremser equation. The dearomatization of pyrolysis gasolines by the {[4empy][Tf2N]+[emim][DCA]} IL mixture would require a higher number of equilibrium stages in the extractor than that employing sulfolane. By contrast, the purity of extracted aromatics would be substantially greater using the IL-based solvent, simplifying the subsequent purification of the BTX.