Selective Separation of Benzene/n-Hexane with Ester-Functionalized Ionic Liquids

The designer nature of ionic liquids (ILs) has driven their exploration and application in countless fields because of their unique phiscochemical properties. In this work, two ester-functionalized ionic liquids (ILs), N-ethyl acetate-N-methylimidazole bis(trifluoromethylsulfonyl)imide ([Eamim][NTf2]) and N-ethyl acetate-N-methylimidazole sulfocyanide([Eamim][SCN]), were prepared. Two ternary systems, benzene-hexane-[Eamim][NTf2] and benzene-hexane-[Eamim][SCN], were investigated in terms of both quantum chemical calculation and liquid–liquid extraction experiments. Quantum chemical calculation results showed that the interaction between ILs and benzene was larger than that between ILs with n-hexane. The liquid–liquid extraction results showed that the selectivity reached 29.55 with [Eamim][NTf2], while the selectivity reached 61.44 with [Eamim][SCN] at 25 °C. The vapor permeation process was conducted through a supported membrane with ILs. The influences of operating temperature and the feed concentration of benzene were investigated. With the increase of temperature, the selectivity of benzene increased at first and then decreased. When the concentration of benzene was 0.5 and the temperature was 35 °C, the selectivity of benzene reached 16.05, while the flux was 22.14 g·h–1·m–2. The stability of the membrane in the vapor permeation was also tested and could remain steady for 60 h.