Performance evaluation and molecular dynamics simulation in the Liquid–liquid extraction process of low transition temperature mixture + n-hexane + 1,2-Dichloroethane

Abstract

Vinyl sulphate, a new battery additive, can significantly improve battery performance, but its production process generates a large amount of n-hexane + 1,2-dichloroethane (DCE) azeotropic mixtures. In this paper, green and efficient Low Transition Temperature Mixtures (LTTMs) were used as solvents to explore their separation performance and mechanism of the n-hexane + DCE azeotrope system. Firstly, the conductor-like screening model for segment activity coefficient (COSMO-SAC) model was used to investigate the effects of the structure and composition of the hydrogen bond donors and hydrogen bond acceptors on the extraction performance. On this basis, three LTTMs were screened out as solvents for the extraction and separation of n-hexane + DCE by combining experiments, which were trimethylamine hydrochloride-levulinic acid 1:2 (LTTM1), tetraethylammonium chloride-levulinic acid 1:2 (LTTM2), tetraethylammonium chloride-pyruvic acid 1:2 (LTTM3). Afterward, Liquid–liquid equilibrium (LLE) experiments were carried out for the ternary system of n-hexane + DCE + LTTMs, and the results showed that the extraction of DCE was favored by low temperatures in the experimental temperature range. Then, molecular dynamics simulation was used to investigate the microscopic mechanism of the extraction and separation of n-hexane + DCE by LTTMs. The results showed that the interaction between LTTMs and DCE was much larger than that between LTTMs and n-hexane, n-hexane and DCE, which was the fundamental reason for the separation of n-hexane + DCE by LTTMs. Finally, the continuous separation process of n-hexane + DCE was simulated using Aspen Plus, and the results showed that LTTMs had good extraction performance and the purity of n-hexane and DCE products could reach 99.6 mol% and 99.5 mol%, respectively. The feasibility and microscopic mechanism of the extraction and separation of n-hexane + DCE by LTTMs were investigated using a combination of experiments and simulations, which provided a methodological reference for the separation of n-hexane + DCE.