Absorption of ethylene dichloride with imidazolium-based ionic liquids

Abstract

A series of imidazolium-based ionic liquids (ILs) with good thermal stability, consisting of [Bmim][BF4], [Bmim][OAc], [Bmim][SCN], [Bmim][DCA], [Emim][DCA], and [Hmim][DCA], were synthesized as absorbents for the absorption of ethylene dichloride (EDC). Among them, the ILs with the anion of [DCA]- possess the best absorption performance of EDC, and [Bmim][DCA] has the EDC absorption capacity of 0.3700 g EDC/g IL (313.15 K, atmospheric pressure) for the given inlet EDC concentration, higher than that of the other Bmim-based ILs. It was demonstrated that the absorption of EDC by [Bmim][DCA] is physical absorption, and the chemical structures of [Bmim][DCA] were consistent after five absorption–desorption cycles as well as no obvious decay in absorption capacity. It was demonstrated that anions of ILs play a more significant role in EDC absorption compared with cations through the analysis of interaction energy and weak interaction obtained by quantum chemical calculation, which also confirms the anions and cations act synergistically on EDC by H-bond and van der Waals (vdW) interaction. Besides, the vapor–liquid equilibrium (VLE) data for [Bmim][DCA]-EDC binary system with different compositions were determined at 303.15–353.15 K and compared with the predicted vapor pressure by the UNIFAC-Lei model. The predicted results show a good agreement with the experimental data, with an average relative deviation (ARD) of 3.98 %, indicating the reliability of the UNIFAC-Lei model.