| Separation of benzene and cyclohexane is among the most important and difficult processes in the petrochemical industry due to their extremely close boiling points. For intensifying the separation of benzene and cyclohexane, three ionic liquids, namely [Bpy][BF4], [Bmim][BF4], and [Bmim][SCN] were evaluated and explored as the extraction solvents. The corresponding liquid-liquid equilibria were experimentally determined for the mixtures of{cyclohexane+benzene+IL} at 298.15 K and atmospheric pressure. The highly reliability of the tie-line data was confirmed by applying the Othmer-Tobias correlation. The separation capabilities of the ILs were evaluated and analyzed in terms of benzene distribution coeffcient and the solvent selectivity. The results show that the ionic liquids studied are suitable solvents for the extractive separation of benzene and cyclohexane. Their separation efficiency can be generally ranked as:[Bmim][BF4]> [Bpy][BF4]> [Bmim][SCN].The experimental LLE data for the three studied systems were correlated with the NRTL equation and the parameters were fitted. The extraction processes were defined and the operation parameters were analyzed at 298.15 K and 101.3 kPa. For the three studied ionic liquids [Bpy][BF4], [Bmim][BF4], [Bmim][SCN], the optimized number of stages and mole ratio of solvent-to-feed are 8,6,12 and 2.2,2.0,3.3, respectively. With the optimized parameters, high mole purity of the cyclohexane product (0.977) can be reached and the recovery rate of cyclohexane and benzene are 96.9% and 98.1%, respectively. It is proved that the studied ILs are promising solvents for the deep separation of benzene from the cyclohexane mixtures. Moreover, the ionic liquid extraction processes are economically applicable due to the considerably simplified process, pollution-free characteristic and recyclable solvents. Thus it can be potentially used as the alternative of the conventional benzene-cyclohexane extractive separation process. |
PDF Full Text Request