Synthesis Of Reactive Distillation And Separation Process For Production Of Dimethyl Carbonate By Transesterification

As an important green solvent,dimethyl carbonate has attracted much attention due to its low toxicity and excellent environmental performance.The process of preparing dimethyl and carbonate by transesterification is mature and the raw material conversion is high,but the dimethyl carbonate-methanol azeotrope will be produced in the synthesis process.In this work,in order to solve the problem of difficult separation of azeotropes,the better extractant was selected by molecular simulation,and the energy-saving and consumption reducing separation process was designed to realize the green and efficient separation of dimethyl carbonate and methanol.The research contents and conclusions of this work are as follows:First,the interaction energy between organic solvents,ionic liquids and deep eutectic solvents and dimethyl carbonate-methanol azeotropic system was investigated by molecular simulation.The results showed that the extraction capacity of dimethyl carbonate-methanol azeotrope separated by different organic solvents was furfural>ethylene glycol>dimethyl oxalate>N,N-dimethylformamide.The extraction capacity of ionic liquids for separating dimethyl carbonate-methanol azeotrope was 1-n-butyl-3-methylimidazole trifluoromethane sulfonate>1-ethyl-3-methylimidazole diethyl phosphate>1-butyl-3-Methylimidazole dibutyl phosphate>1-ethyl-3-methylimidazoline bis（trifluoromethylsulfonyl）imine.The extraction capacity of different DESs for separating dimethyl carbonate-methanol azeotrope was choline chloride:urea（1:2）>choline chloride:glycerol（1:2）>choline chloride:malonic acid（1:2）>choline chloride:ethylene glycol（1:2）.Then,based on the selected better extractant,different energy-saving processes were designed to realize the efficient separation of dimethyl carbonate-methanol azeotrope.Firstly,the reactive distillation,reactive extractive distillation and reactive dividing-wall extractive distillation processes were designed with furfural as extractant.The total annual cost of reactive dividing-wall extractive distillation process was 1.48×10~6$/Y compared with reactive distillation process,the economic cost was reduced by21%and the carbon emission was reduced by 10%.A common extractive distillation process coupled with pervaporation technology with[BMIM][OTF]as extractant was designed to separate dimethyl carbonate-methanol azeotrope.The research results showed that the economic and environmental performance analysis results of this process were better than those of common extractive distillation,the total annual cost was reduced by 17%compared with common extractive distillation,and the emission of acid gases（carbon dioxide,sulfur dioxide and nitrogen oxides）was reduced by 49%.In this study,based on molecular simulation,the better extractant was selected,and the process design and process intensification of the synthesis of dimethyl carbonate by transesterification were carried out.This study has important guiding significance for the synthesis of dimethyl carbonate by transesterification and the green and efficient separation of dimethyl carbonate-methanol azeotrope in practical industry.