Mechanism analysis and sustainability evaluation of imidazole ionic liquid extraction based on molecular dynamics

Liquid-liquid extraction is often used in industry because of its advantages of low energy consumption and low cost. In this study, ionic liquids were used to separate ethyl acetate / n-hexane system. Molecular dynamics simulation was used to study the extraction mechanism of ionic liquid / n-hexane / ethyl acetate from a microscopic point of view. The results showed that the extraction capacity of ionic liquids for n-hexane-ethyl acetate mixture was [HMIM][PF6] > [HMIM][NTF2] > [HMIM][OTF] > [OMIM][PF6]. Anion plays a more important role in the extraction of ethyl acetate. The results showed that [HMIM][PF6] had better extraction effect. However, [PF6]− is easily hydrolyzed to produce HF, which causing great harm to the environment and equipment. Therefore, [HMIM][NTF2] is more suitable for the separation of ethyl acetate-n-hexane mixed system. In addition, Aspen Plus was used to simulate industrial processes to separate the ethyl acetate-n-hexane azeotropic system and recover the ionic liquid. The recovery rate of ionic liquid is 99.98%, and the mass fraction of purified n-hexane is 99.32%. In addition, the recovery rate, economical evaluation and environmental impact of [HMIM][NTF2] and acetonitrile as extractants were compared.