Preparation Of Solid Base Catalysts For Synthesis Of Glycerol Carbonate And Its Performance Research

Biodiesel is a kind of ideal alternative fuel.Its production process is accompanied by a large amount of by-product glycerin,resulting in an oversupply of glycerol.The development of glycerol derivatives is an effective way to deal with excess glycerol.Glycerol carbonate（GC）is a chemical with high added value.It is widely used in many fields such as pharmaceuticals and cosmetics.It could be converted from glycerol.Among the various synthetic routes,the reaction path for preparing GC by transesterification from glycerol and dimethyl carbonate（DMC）is favored due to factors such as mild required conditions and high yield of main products.In this study,composite metal oxide catalysts were synthesized by two simple routes for the reaction of transesterification of glycerol and DMC to produce GC.By investigating the differences between the catalytic effect caused by the composite mode and the reaction conditions,improvements were made.The conclusions obtained are as follows:（1）A series of BaO-Li₂O/CeO₂ catalysts were prepared by impregnating.When the total loading volume is 10%and n（Ba）/n（Li）=1/2,the synthesized 10%（1Ba:2Li）/CeO₂（calcined at 600°C for 5 h）catalyst has the best effect.By adjusting the reaction conditions,at 85°C,n（glycerol）/n（DMC）=1/3,5 wt.%catalyst of glycerol,and the reaction is performed for 6 hours to obtain a maximum conversion rate of glycerin of 96.50%without byproducts.The physicochemical properties and structural composition of the catalyst were analyzed.The results showe that BaO and Li₂O were highly dispersed on the support.Li⁺occupied part of the Ba²⁺position in the BaO lattice,which contributed to the generation of a large number of strongly basic sites with the promoted glycerol conversion.After repeated use for four times,the catalytic activity remained high in the reaction.（2）Mixed bimetal oxide CeO₂-ZnO catalysts with different Ce/Zn ratios were prepared by co-precipitation method.The catalyst Ce_0.5Zn_0.5O（calcined at 550°C for5 h）with equimolar ratios of Ce and Zn have the highest activity.Adjust the reaction temperature and the molar ratio of the reactants to optimize the performance of the catalyst:at 85°C,the glycerol/DMC molar ratio is 1/3,3wt.%Ce_0.5Zn_0.5O Of glycerol,1 h,and the glycerin conversion rate is 96.17%GC selectivity reaches 100%.The physical and chemical properties of the catalyst samples were determined.The results showed that the synthesized catalysts were mesoporous materials with considerable specific surface area.The sample prepared contains both weakly basic sites and strongly basic sites,the latter playing a major catalytic role.Zn²⁺was doped into CeO₂lattice to form surface defects.Thus,strongly basic sites were generated.