Extraction Separation Benzene From Cyclohexane Using N,N-dimethylacetamide And Ammonium Thiocyanate And Its Electrochemical Performance

Benzene and cyclohexane which share several similarities in chemical structure andproperties will form an azeotrope and cannot be separated by simple distillation. In industry,extractive distillation and azeotropic distillation are two typical methods to separate benzeneand cyclohexane, however high expenses, complex process, high energy consumption andlimit of vapor-liquid equilibrium inspire a novel efficient method to separate the benzene andcyclohexane system.Liquid-liquid extraction method is an alternative way to separate compounds whichcannot be separated by simple distillation. In this subject, we chose this method to separatebenzene and cyclohexane system. We found that DMAc+NH₄SCN showed excellentselectivity in extracting benzene out of the system and the LLE data for quarternary systemsof benzene+cyclohexane+DMAc+NH₄SCN was also measured. By comparing thesefigures, selectivity coefficients of DMAc+NH₄SCN were also calculated. It was found thatas the content of NH₄SCN in extraction grow, the selectivity coefficient grow and with morebenzoate in the system, the selectivity coefficient was fewer. When use DMAc+NH₄SCN asextraction to separate benzene and cyclohexane, the selectivity coefficients were between1.88～15.00and the partition coefficients were between0.23～0.81. After multistageextraction, mole fraction of cyclohexane in raffinate phase was as high as93.9%and mostpart of DMAc+NH₄SCN was in raffinate phase which made post-processing convenient.Considering the high selectivity of DMAc+NH₄SCN, the extraction reagent can separatebenzene and cyclohexane system and is more efficient for the system with large number ofcyclohexane. Cyclic voltammetry, electrochemical impedance and charge-discharge cycle testwas applied to perform the electrochemical properties of the ultracapacitors with10%NH₄SCN+90%DMAc as electrolyte. The specific capacity and equivalent series resistanceof the ultracapacitors were18.82F/g and4respectively and the ultracapacitors performedgood cycle performance.Draw the phase diagram based on the figures. The Othmer-Tobias equation and NRTLequation were used to correlate the experimental results and Correlation coefficient is higher,the maximum is99.9%, the rest of the correlation coefficient were greater than90.5%, therelative standard deviation was0.0066. From the calculate result, the NRTL equation is suitable to correlate the benzene+cyclohexane+DMAc+NH₄SCN quaternary system.ChemCAD was used to simulate how the flow ratio, constituent of mixture and extractionreagent affect the separation effect and the results showed DMAc+NH₄SCN had a goodseparation effect on benzene and cyclohexane especially when mass ratio of DMAc+NH₄SCN was35/65and ratio of benzene and cyclohexane was10/90in the feed solution, theyield coefficient of benzene was as high as89.9%. This also demonstrated DMAc+NH₄SCNwere a technique suitable extraction regent for separation of benzene and cyclohexane.