Molecules Design Of Ionic Liquid As Mass Separation Agent In Extractive Distillayion

Ionic liquids (ILs) have many unique attributes, e.g. negligible vapor pressure, highboiling point，good thermal stability and high separation ability, which make them potentialbeing used in chemical reaction and Chemical separation processes. A molecular designmethod based on COSMO-SAC was proposed for the solvent selection in extractivedistillation, and this method was verified by vapor-liquid equilibrium experiments.24kinds of anions and176kinds of cations of ILs was chosen, the-profiles wereobtained based on the charge densities. Adatabase contains-profiles of anions and cationswas established. The infinity activity coefficient of the component in IL were calculated byCOSMO-SAC. Selectivity and solubility were used as screening indexes for the screeningof ILs. VLE data for acetonitrile-water system and cyclohexane-ethanol system weremeasured to verify this method.For acetonitrile-water system，three ILs ([EMIM]OAc、[4MePy]OAc、[HDMIM]OAc)which with high selectivity and high solubility were chosen according this method. VLEdata were measured for the three ternary systems containing acetonitrile, water and ILs at101.3KPa. Results showed that the three ILs were effective to the enhancement of relativevolatility of the acetonitrile-water system. The azeotropic point was eliminated when themass fraction of IL reached30%. The separation ability of ILs were [HDMIM]OAc>[4MePy]OAc>[EMIM]OAc when the mole fraction of acetonitrile in raw material lessthan0.75, while the order were [HDMIM]OAc>[EMIM]OAc>[4MePy]OAc when themole fraction of acetonitrile in raw material greater than0.75. Wilson model parameterswas calculated and predict VLE data of acetonitrile-water-IL systems by activity coefficientmethod with overall average relative deviation of4.92%.For cyclohexane-ethanol system，three ILs ([OMIM]Cl、[BDMIM]Cl、[BMIM]Cl)which with high selectivity and high solubility were chosen according this method. VLEdata were measured for the three ternary systems containing cyclohexane, ethanol and ILsat101.3KPa. Results showed that the three ILs were effective to the enhancement ofrelative volatility of the cyclohexane-ethanol system. The azeotropic point was eliminatedwhen the mass fraction of IL reached30%. The separation ability of ILs were [BMIM]Cl>[OMIM]Cl>[BDMIM]Cl which conform to the molecular design. Wilson modelparameters was calculated and predict VLE data of cyclohexane-ethanol-IL systems byactivity coefficient method with overall average relative deviation of5.45%.In conclusion, the molecular design method based on COSMO-SAC which wasproposed in this paper is a practical, effective and accurate molecular design method for thesolvent selection in extractive distillation. It provided basic data and theory instruction for further industrial application of ionic liquids as mass separating agent.