A Study Of The Process Of Extractive Distillation Of Azeotropes From Ionic Liquid-based Mixed Solvents In A Dividing-wall Column

Tetrahydrofuran,methanol and sec-butyl alcohol are important chemical raw materials,which are widely used in chemical,energy and medical fields.However,the process of hydrolysis of sec-butyl acetate to produce sec-butanol is prone to form sec-butanol-water azeotropic mixtures,while tetrahydrofuran-methanol-water mixtures are also common azeotropic mixtures in industry.These azeotropic mixtures are usually difficult to be separated by conventional distillation,which will not only cause environmental pollution but also generate waste of resources.Extractive distillation is an effective method for separating azeotropic mixtures,but it is still an energy-intensive process,and the use of efficient extractants combined with process intensification techniques is an effective way to reduce the energy consumption of such processes.The main works are as follows.（1）The selectivity and solubility of 240 ionic liquids for tetrahydrofuran-methanol-water mixtures were compared based on COSMO-RS model calculations;the effects of five organic solvents,including dimethyl sulfoxide,on the vapor-liquid equilibrium of tetrahydrofuran-methanol-water mixtures were compared separately based on the relative volatility.（2）Based on the COSMO-RS model,the molecular polarity of the components to be separated and the ionic liquid was studied by their molecular charge density distribution curves（σ-profile）;the interaction energy between the anion and cation of the ionic liquid and the molecules of each component of the mixture was calculated based on quantum chemical theory,and the interaction type was analyzed from the visualization point of view by the independent gradient model（IGM）.（3）Process simulation of tetrahydrofuran-methanol-water ternary extractive distillation in different configurations was designed and compared based on Aspen Plus software,and process enhancement of the process was carried out by combining ionic liquid-based mixed solvents and splitting the dividing wall column.（4）The selectivity and solubility of ionic liquids for sec-butanol-water mixtures were calculated and compared based on COSMO-RS model;the effects of five organic solvents on the vapor-liquid equilibrium of sec-butanol/water mixtures were calculated separately based on the relative volatility;the simulation of the hydrolysis process of sec-butyl acetate under different configurations was carried out based on Aspen Plus software,and the combination of ionic liquid-based solvent mixture and partitioning of the dividing wall column for The process intensification was carried out by combining ionic liquid-based mixed solvents and a split door tower.Based on the calculation results of COSMO-RS model,and considering the cost and physical and chemical properties,1-ethyl-3-methylimidazole acetate（[EMIM][AC]）was finally selected as the best ionic liquid.According to the vapor-liquid equilibrium analysis,dimethyl sulfoxide was selected as the best organic solvent.According to theσ-profile and IGM analysis,the interactions between[EMIM][AC]and the components to be separated were dominated by hydrogen bonds.For the tetrahydrofuran-methanol-water ternary extractive distillation,the direct extraction dividing wall column process using an ionic liquid-based mixed extractant reduced the total annual average consumption,CO₂ emission and energy consumption by14.22%,17.58%and 17.58%,respectively,compared with the conventional extractive distillation process.For the hydrolysis reaction of sec-butyl acetate,the reactive extractive distillation with ionic liquid-based mixed extractants in a split-door tower process can reduce energy consumption,CO2 emissions and economic costs by 28.81%,28.81%and 28.38%,respectively,compared with the conventional extractive distillation process.The results show that ionic liquid-based hybrid solvents can effectively overcome the limitations of high volatility of organic solvents and high cost of ionic liquids to achieve a more energy-efficient and environmentally friendly chemical process.Combined with the dividing wall column process,the process intensification is enhanced to further reduce the economic cost,energy consumption and environmental impact in the hydrolysis reaction extractive distillation of sec-butyl acetate and tetrahydrofuran-methanol-water ternary extractive distillation processes,which is a guideline for industrial applications.