Study On Cu/SiO₂Catalyst Of Dimethyl Oxalate Hydrogenation

Ethylene glycol, an important chemical material, is widely used in all walks oflife. There are many ways to obtain it and better than other approaches, sythesisethylene glycol through C1ways is of great interest. The researches on the catalystsfor hydrogenation of dimethyl oxalate to ethylene glycol are mostly focused on thekinds of catalyst carriers, the comparison of catalysts preparation methods, theeffection of doping metal ions, the optimization of react conditions and so on.There are little papers about some certain method preparing catalysts. In thisdissertation, Cu/SiO2catalysts were prepared by ammonia-evaporation method, theparameters and conditions of which were investigated detailedly. Besides,considering the deactivation behavior of copper-based catalysts at the hightemperature, the catalysts were modified by Ce to improve the thermostability. Thefollowing results were obtained.(1) The higher the ammonia evaporation rate is, the faster and more uniformdistribution of copper precursors upon the SiO2support, and the coagulationand growth of the Cu particles could be reduced. More than99.9%DMOconversion and94.4%EG selectivity could be obtained under the optimizedreaction conditions of T=200℃, P=3.0MPa, LHSV=0.4h-1, molar ratio ofhydrogen to DMO (H:DMO)=80:1;(2) As to copper-based catalysts, the contents of Cu have a great influence on thecatalytic performance of catalysts. The effection would be weakened if thecontent of Cu is low; but if the content of Cu is in large doses, the copper ionwill gather together and the copper particles will grow up, which wouldinactivate the catalysts. Therefore the proper content of Cu is good forimproving the catalytic ability of Cu/SiO2catalysts. It was found that highDMO conversion and EG selectivity could be obtained when copper accountedfor20percent of the catalyst;(3) Given that the ammonium hydroxide forming the aqueous cuprammoninacomplex with copper is one of the materials to prepare the Cu/SiO2catalystswhen choosing ammonia-evaporation method, its content also affects thecatalytic activity of catalysts. And the proper content of ammonium hydroxidewas7mL after investigating.(4) To improve the thermostability of copper-based catalysts because of the lowmelting point of copper, a series of Cu/SiO2catalysts modified by Ce were prepared by three different methods. It turned out that the catalysts exhited thegood thermostability after introducing Ce whichever method to choose. Theright Ce content was0.6%or0.8%when adding Ce before the catalystprecursors forming. And0.4%or0.6%Ce would be good when adding Ce afterthe catalyst precursors forming.