Combination Design Of Imiidazole Ionic Liquids And Extractive Distillation For The Alcohol Ester Separation Process

Ionic liquids,as green solvent,have attracted much attention in the chemical separation process.Because of the variety of ionic liquids and relatively new ones,there are no relevant physical parameters about them in Aspen Plus database.The study on the selection methods and process flow of ionic liquids becomes very important.In this work,the azeotropic mixture of methyl acetate and methanol produced in the production of polyvinyl alcohol was studied.COSMO-SAC model and Material Studio software were used to select the appropriate imidazole ionic liquids solvent for separating the azeotropic system by extractive distillation based on quantum chemical calculation.The internal relationship between the ionic liquids and azeotropes were explored.The steady-state process of extractive distillation of ionic liquids was designed and optimized.The economy of different ionic liquids solvent were investigated.In the work,the extraction distillation process of methyl acetate-methanol system with imidazole ionic liquids was studied.Based on 25 kinds of imidazole ionic liquids randomly composed of five anions and cations,the infinite dilution selectivity of methyl acetate to methanol was calculated using COSMO-SAC model and infinite dilution selectivity formula.Thus,[HMIM][Cl] and [BMIM][Cl] were selected as the most suitable solvent for the separation of methyl acetate and methanol mixtures.The intrinsic hydrogen bonding effect of the ionic liquid for the azeotrope separation was analyzed from the qualitatively ?-profiles and differential charge density distribution,quantitatively bond length and bond energy.At the same time,the experimental data of vapor-liquid equilibrium show that [HMIM][Cl] and [BMIM][Cl] can break the azeotrope.To realize the steady-state design of extractive distillation process for methyl acetate-methanol system containing ionic liquids,the thermodynamic parameters of [HMIM][Cl] and [BMIM][Cl] were regressed by using the thermodynamic experimental data and formulas.The fitting values were in good agreement with the experimental values.By comparing NRTL model with UNIFAC-Lei model,the results show that the NRTL model has less error with the experimental values.The extractive distillation process of methyl acetate-methanol azeotrope system containing ionic liquids was designed by Aspen Plus software.Based on the minimum annual total cost TAC,the optimal operating parameters and corresponding equipment parameters of extractive distillation process were obtained.The results showed that TAC in the separation process using [HMIM][Cl] as solvent was reduced by 16.5% compared with [BMIM][Cl] in the same purity of methyl acetate and methanol reaching 99.91 mol%,which suggested that it had the advantages of energy saving and consumption reducing.