Liquid–Liquid Extraction of Benzene and Cyclohexane Using Sulfolane-Based Low Transition Temperature Mixtures as Solvents: Experiments and Simulation

The separation of benzene and cyclohexane is considered to be one of the most challenging processes in the petrochemical industry. In this paper, low transition temperature mixtures (LTTMs) were used as solvents for the separation of benzene and cyclohexane. The selected LTTMs were sulfolane–tetrabutylammonium bromide 5:1 and ethylene glycol–trimethylamine hydrochloride 5:1, and liquid–liquid equilibrium (LLE) data of benzene–cyclohexane–LTTMs were experimentally determined at 40 °C under a normal atmosphere. Moreover, the effects of the mole ratio of hydrogen bond donor (HBD) sulfolane and hydrogen bond acceptor (HBA) tetrabutylammonium bromide on extraction performance were also observed based on the LLE data. It is found that, when the mole ratio of sulfolane to tetrabutylammonium bromide is 5:1, LTTM has the best extraction performance. In addition, the LLE data of the benzene–cyclohexane–LTTMs ternary system were used to fit parameters of the NRTL activity coefficient model. Based on the NRTL model the continuous extraction process was simulated and the operating parameters were obtained, and high product purity (cyclohexane 0.997) and high recovery efficiency (cyclohexane 93.28% and benzene 98.25%) can be achieved. In conclusion, the LTTM sulfolane–tetrabutylammonium bromide 5:1 is a promising solvent for the extractive separation of benzene–cyclohexane mixtures.