Liquid-liquid Equilibrium For Extraction Separation Benzene And Cycloheane Using N, N-Dimethylformamide And Potassium Thiocyanate

Separation of benzene and cyclohexane is among the most important and difficult processes in the petrochemical industry. Cyclohexane is produced by catalytic hydrogenation of benzene. The unreacted benzene remain in the reactor's effluent stream and must be removed for pure cyclohexane recovery. Separation of benzene and cyclohexane is difficult by a conventional distillation process because these components form close boiling point mixtures at the entire range of their compositions. Presently, azeotropic distillation and extractive distillation are used for this separation. These two processes, however, suffer from complexity and high energy consumption. For all these reasons, the industry has always been eager to look for a viable alternative to the conventional benzene/cyclohexane separation processes.Extraction is a viable alternative to the conventional techniques both from economical and technical points of view. In this work, the complex solvent system, potassium thiocyanate dissolved in DMF, is found to be a good extractant for the separation of benzene from cyclohexane because the solvent is high selective and very cheap. The properties of complex solvent were investigation. Phase equilibrium data are required for the evaluation of solvent combinations and design of extraction equipment, so the Experimental liquid-liquid equilibrium data were measured for benzene+ cyclohexane + DMF + KSCN at 303.15 K and atmospheric pressure. The selectivity coefficients of DMF+KSCN for benzene are 2 to 12. Distribution coefficients of DMF+KSCN for benzene are 0.2 to 0.8. The results revealed that the selectivity coefficients increased with the decreasing of the concentration of benzene in the raffinate, and increased with the increasing of the mass fraction of KSCN in DMF+KSCN mixture. Considering the high selectivity for benzene, DMF+KSCN may be used as a potential extracting solvent for the separation of benzene and cyclohexane.The experimental data was correlated using the Othmer-Tobias correlation, and triangular phase diagrams was drawing according to the liquid-liquid equilibria data(LLE). The LLE data were analyzed using NRTL model with temperature-dependent binary parameters determined from the experimental LLE data, both as programmed by the CHEMCAD6.0.1 simulator. Based on the analysis of these data, the NRTL model represented the experimental data with sufficient accuracy as revealed from the very small values of the root mean square error(0.00-0.05) and the average absolute deviation(0.00-0.05) in composition. The feasibility of extraction benzene from cyclohexane used DMF+KSCN was investigation by ChemCAD6.0.1 simulator. The emulation results indicated that DMF+KSCN were able to use extraction benzene from cyclohexane. Considering the high selectivity for benzene, DMF+KSCN may be used as a potential extracting solvent for the separation of benzene and cyclohexane.