| A computer-aid molecular design method based on COSMO-RS was proposed for the solvent selection in extraction, and this method was verified by liquid-liquid equilibrium experiments.According to the mixture to be separated, Materials Studio was utilized to calculate the screening charge densitiesσ*, theσ-profiles were obtained based on the charge densities. A database containsσ-profiles of 25 kinds of anions and 190 kinds of cations was established. The infinity activity coefficient of the component in ionic liquid were calculated by COSMO-SAC. The distribution coefficient, solvent loss, selectivity and solvent power were used as evaluation function for the molecular design solvent for extraction.Due to the lack of melting points of ionic liquids, A prediction equation of ionic liquid was obtained by nonlinear fit of 163 melting points of ionic liquids, based on the thermodynamic energy-like parameter, screening cavity area parameter, which are produced from COSMO calculation.The solvents for separation of methyl acetate-methanol system by extraction were selected by the molecular design method. The liquid-liquid equilibrium of methyl acetate-methanol-1-ethyl-3-methyllimidazolium acetate([EMIM][Ac]) was measured, and the experimental results show that the molecular design method is effective.The parameter of NRTL equation for methyl acetate -methanol-[EMIM][Ac] were correlated by the liquid-liquid equilibrium data. The extraction process for the separation of methyl acetate–methanol by ionic liquid [EMIM][Ac] was simulated by the software ChemCAD, and the effects of theoretical plate number and solvent flowrate to extraction process were investigate by the simulation results. |
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