Effect Of Different Molding Methods On Carbonate Transesterification In Gas-liquid-solid States

Dimethyl carbonate（DMC）is an important organic synthesis intermediate and a green organic solvent with excellent performance.Dimethyl carbonate is now commonly produced in industry by the transesterification of ethylene carbonate（EC）with methanol.The use of easily separable and recyclable heterogeneous catalysts can avoid the problems of homogeneous catalysts,which are easily deactivated by water,cannot be recycled and are difficult to separate.However,in the real reaction condition,the temperature in the reaction-rectification process is below 70℃.EC and EG exist in liquid form and are less mobile and tend to adhere to the catalyst surface,limiting the efficiency of mass transfer between the catalyst and the raw material.The catalysts prepared by suitable molding methods have a appropriate morphological structure and give full play to their catalytic properties.Based on this,the effect of different molding methods on the transesterification reaction between ethylene carbonate and methanol was investigated.The choice of a better molding method to increase the external surface area of the catalyst is more favourable to mass transfer,allowing the catalyst to perform more effectively.The order of catalytic activity follows natural sieving>extruding strips>rolling balls>>tableting.The effect of additives on catalyst activity and strength was investigated by adding different additives.It was found that the order of the ability of different types of pore-molding agents to improve catalyst activity was methyl cellulose>citric acid>starch>carbamide>none-agent>ammonium bicarbonate,while the optimum addition of the pore-molding agent citric acid was 20%.The optimum addition of sesbania powder as extruder was 1%,and the strength increased by 34.0 N/cm compared to the catalyst without sesbania powder;the optimum addition as a pore-molding agent was 0.5%,and the DMC yield increased by 11.1%compared to the catalyst without sesbania powder by adding 0.5 wt%of sesbania powder at a mass space velocity of 0.625 h^-1.Characterization showed that the specific surface area,pore diameter and pore volume of the catalyst prepared by extrusion were large,and the alkalinity of the catalyst increased slightly after adding sesbania powder.The relationship between the infiltration volume and the catalyst activity was investigated by experimentally determining the infiltration thickness between the catalyst and the raw material and mathematically modelling the infiltration volume for different shapes of catalysts.This research was found that the larger the catalyst infiltration volume of the raw material,the higher the catalyst activity,and the pattern was consistent with the relationship between surface area and catalyst activity.