Separation of benzene and cyclohexane is one of the most important processes in the petrochemical industry. However, due to their close boiling points and azeotrope formation, it is difficult to separate cyclohexane and benzene by conventional distillation processes. In this work, five thiocynate-based ionic liquids were investigated as solvent for separation of benzene and cyclohexane using extractvie distillation. The separation performances of the ionic liquids were evaluated in terms of their selectivity for benzene and relative volatility of the components the presence of the ionic liquids. The relative volatility and selectivity values were obtained from the experimental vapour-liquid equilibrium measured using head space gas chromatography.The effect of the structural variations of the ionic liquids on the separation performance was explained by COSMO-RS model. The result shows the ionic liquids studied can break the azeotropic mixture and increase the relative volatility of the cyclohexane to benzene. Copyright © 2013, AIDIC Servizi S.r.l.