Study On Silver Based Catalysts For Hydrogenation Of Dimethyl Oxalate To Methyl Glycolate

Methyl glycolate?MG?is an important chemical intermediate products and chemical raw materials,which is widely used in the synthesis of medicine,fine chemicals and so on.With the rapid development of Chinese economy,the demand of MG is also increasing.Currently,the main industrial approach to producing MG is petrochemical method and exists heavy corrosion and pollution.Besides,being affected by crude oil resource shrinks and oil crisis,and combining with the energy structure in China,the MG producing route via syngas is a more economical and environmentally-friendly way.First,the Cu/SiO₂ catalysts prepared by ammonia evaporation method were used to investigate the technological conditions for the dimethyl oxalate?DMO?hydrogenation to MG.The study shows that when the reaction temperature is 200 oC,reaction pressure is 2.5 MPa,H2/DMO is 50 and liquid hourly space velocity?LHSV?is 1.5 h-1,the yield of MG is the highest?65.5%?,the DMO conversion is 91% and the MG selectivity is 72%.It demonstrated that copper based catalyst is hard to control the reaction stage in the hydrogenation of DMO,so the yield of MG is not easy to be improved.Then,a series of silver based catalysts were developed to study the relationship between catalytic performance and the support structure,and the influence of silver surface chemical state on the hydrogenation of DMO to MG.This dissertation provides instructive research for the development of new and efficient silver based catalysts.Hydrothermal crystallization method was adopted to synthesis the hierarchical pore structure of KCC-1 material.The Ag/KCC-1 catalysts prepared by incipient-wetness impregnation method with different silver loadings for DMO hydrogenation to MG were investigated.The 15wt% Ag/KCC-1 exhibited better catalytic performance due to larger surface area of Ag.The best performance was achieved when LHSV is 1.5 h-1,the DMO conversion is 97.8%,the MG selectivity is 92.2% and the yield of MG is 90.2%.Moreover,KCC-1,SBA-15 and MCM-41 supported silver catalysts were compared.The Ag/KCC-1 catalyst showed better catalytic performance because silver particles were not easy to block the pores of the catalyst,so the catalysts had better silver dispersion,and the hierarchical pore structure is beneficial for the accessibility of active sites.Ti-KCC-1 support and the catalysts were prepared to investigate the effect of Ti on the catalytic performance of the DMO hydrogenation to MG.The characterization showed that the interaction between Ti and Ag suppress the aggregation of Ag,thus improve the dispersion of the catalyst.The electron transfer from Ti to Ag decreased the reduction temperature of the catalyst,accelerated the adsorption of hydrogen molecule on Ag nanoparticles,but also weakened the adsorption of carbonyl.10Ag/Ti-KCC-1-0.02 catalyst with the highest dispersion showed better performance?...