Separation of benzene and cyclohexane azeotrope mixture using 1-ethyl-3-methylimidazolium ethyl sulfate ionic liquid using extractive distillation

Most of the cyclohexane used for various industrial applications is largely produced through catalytic hydrogenation of benzene and the separation of cyclohexane from the unreacted benzene is industrially significant. However, it is tough to separate cyclohexane from benzene by conventional distillation processes since these components have close boiling points and form an azeotrope mixture. Currently, extractive distillation is commercially used for the separation of cyclohexane from benzene using conventional solvents (entrainers) such as sulfolane, dimethyl sulfoxide, N-formylmorpholine, and N-methylpyrrolidone. However, separating benzene and cyclohexane with extractive distillation with these solvents makes the process complex and consumes high energy. On the other hand, ionic liquids are considered green and potentially environmentally friendly, hence have been attracting attention in replacing conventional solvents (entrainers) in extractive distillation because of their unique properties. In this work, 1-ethyl-3-methylimidazolium ethylsulfate ([EMIM][EtSO4]) was used for the separation of cyclohexane from benzene using extractive distillation. The performance of [EMIM][EtSO4] was evaluated by measuring the isothermal vapour-liquid equilibrium (VLE) for benzene, cyclohexane, and [EMIM][EtSO4] ternary mixture at 353.15 K. The isothermal VLE was measured using Head Space Gas Chromatography (HS-GC). Moreover, the VLE data was also predicted using COSMO-RS and compared with the experimental values. The addition of [EMIM][EtSO4] eliminated the azeotrope and increased the relative volatilities of benzene and cyclohexane resulting in their separation. The performance of [EMIM][EtSO4] on the benzene and cyclohexane system was compared with dimethyl sulfoxide. The current ionic liquid shows higher relative volatility compared to dimethyl sulfoxide showing this ionic liquid can be used for the separation of benzene and cyclohexane using extractive distillation.