Journal of Applied Science Issue (1) September (2018) 10 TERNARY LIQUID-LIQUID EQUILIBRIA FOR {BENZENE + CYCLOHEXANE + DIFFERENT IONIC LIQUIDS } at T= 298.2 K and P=1 atm: EFFECT OF CATION AND ANION ON SEPARATION PERFORMANCE. Salem A. Sakal College of Engineering, Chemical Engineering Department , Sabratha University, Libya Corresponding author: salemsakal@yahoo.com,Tel: +218918201257 Abstract Ionic liquids (ILs) based on imidazolium and pyridinium cations and different types of anions containing transition metals were investigated for extraction of benzene from cyclohexane. The Liquid-liquid equilibrium (LLE) data are presented for six ternary systems of (Cyclohexane + Benzene + an ionic Liquid) at 298.15 K and atmospheric pressure. The ILs used in these systems are [Bmim][FeCl 4 ], [Bmim][AlCl 4 ], [Bmim][CuCl 2 ], [BuPy][FeCl 4 ]), [BuPy][AlCl 4 ], and [C 6 Py][FeCl 4 ] were all prepared in the lab. The influence of cation and anion structure of ILs on the separation selectivity and capacity for aliphatic/aromatic mixtures was analyzed. The results indicate that most ILs investigated shows both higher extractive selectivity and capacity for the aromatic components for the systems studied herein, suggesting they can be used as promising extracts for the separation of aliphatic/aromatic mixtures. The LLE data were well correlated by the non-random two-liquid (NRTL) model of non-electrolyte solutions with overall ARD deviation being about 0.0001 in term of the mole fraction based activity. Keywords: Liquid-liquid equilibria; ionic liquids; NTRL; aromatic compound; aliphatic compound. Introduction The separation of aromatic from aliphatic compounds is of great importance for the petrochemical industry, especially when to meet the high demand of aromatic compounds by the chemical industry, and the strict legal restrictions on the content of aromatics in gasoline. The aromatic hydrocarbons are separated from naphtha using a typical liquid-liquid extraction process (Hamid and Ali, 1996). Some conventional organic chemicals, such as sulfolane, (Rappel, Nelson and Mattedi, 2002) N-formylmorpholine, (Dong Chu, Hong and Hao, 2007), Nmethylimidazolor N- ethylimidazole, (Wang, et al., 2008), glycols, (Al-Sahhaf and Kapetanovic, 1996) [5-7] propylene carbonate, (Ali, et al. 2003) [8] or combinations of solvents, are used for the extraction of aromatics. However, these organic extracting solvents are generally toxic, volatile, flammable, and hard to be recycled facially due to their mutual solubility with the naphtha to be separated. In separations, a distillation step is