Extractive Distillation of Ethanol-Cyclohexane Azeotrope Using Ionic Liquid as Extractant

The effect of different ionic liquids on relative volatility of ethanol-cyclohexane system was examined at 0.101 MPa.The effects of solvent ratio on relative volatility of ethanol-cyclohexane system,and flow rate of ionic liquid and reflux ratio on purity and output of overhead fraction of the extractive distillation column with ionic liquid were studied.Repeated experiments were carried out under the optimum experimental conditions.The results show that the azeotropic point of ethanol-cyclohexane system is eliminated in extractive distillation with ionic liquid and relative volatility of cyclohexane to ethanol increases.The purity of cyclohexane is over 99.8% when [bmim]PF6 is used as extractant,solvent ratio 0.5,flow rate of ionic liquid 6 mL/min and reflux ratio 3.By flash distillation of residue,ethanol and ionic liquid can be separated.The recovery rate of ethanol is over 99.9% and the recycled usage of ionic liquid does not impair the separation performance.