Separation of BTEX from a naphtha feed to ethylene crackers using a binary mixture of [4empy][Tf2N] and [emim][DCA] ionic liquids

摘要

The separation of BTEX from petroleum streams with aromatic contents between 20 and 65 wt.% is usually made by liquid-liquid extraction. Nevertheless, there are no technologies currently available to perform the separation of aromatics from streams with an aromatic content lower than 20 wt.%. In this work, we have studied the separation of BTEX from a naphtha feed to ethylene crackers with a total aromatic content equal to 10 wt.%. Aromatics are not converted to olefins in ethylene crackers and their presence increases operating costs and the size of furnaces. Because of this, the separation of BTEX from this stream has been studied using the binary IL mixture formed by the 1-ethyl-4-methylpyridinium bis(trifluoromethylsulfonyl)imide ([4empy][Tf2N] and the 1-ethyl-3-methylimidazolium dicyanamide ([emim][DCA]), since this IL mixture previously showed adequate extractive properties in the BTEX extraction from reformer gasoline. The separation of BTEX from the naphtha has also been studied using sulfolane, the most used solvent in aromatic extraction at industrial scale. The influence of temperature and solvent to feed ratio on several extractive properties has been carried out from the experimental results employing both extraction solvents. The Kremser equation has been used to simulate the countercurrent extraction columns in the separation of BTEX from the naphtha, studying the effect of the number of equilibrium stages in the extraction yield of BTEX and in the purity of the aromatics obtained. (C) 2015 Elsevier B.V. All rights reserved.