Study On CuZr/SiO₂ Catalyst For Hydrogenation Of Dimethyl Oxalate To Ethylene Glycol

As an important basic chemical raw material,ethylene glycol can be widely used in antifreeze,polyester,surfactant and other industries.With the rapid development of the world economy,the demand for ethylene glycol is increasing year by year.Combined with the characteristics and China’s situation of energy and resources which is poor oil,little gas and rich in coal,it is of great economic and strategic significance to develop C1 chemical technology for the production of bulk chemicals by utilizing coal-based energy.Among them,the process of producing ethylene glycol（EG）via the hydrogenation of dimethyl oxalate（DMO）from syngas has attracted wide attentions due to its high atomic economy,low resource cost and environmental friendliness.Combined with the advantages of high surface area of Cu/SiO₂ and strong interaction with interfacial property of Cu/ZrO₂ catalysts,the preparation method of CuZr/SiO₂ catalyst was further studied.Three methods of hydrolysis precipitation method,ammonia evaporation method and co-precipitation method were used to prepare the catalysts,and the catalytic performances of different methods in the hydrogenation of dimethyl oxalate to ethylene glycol were explored.Different with the conventional ammonia evaporation and co-precipitation method,the hydrolysis precipitation method is similar to the pseudo homogeneous reaction,which is conducive to disperse the copper and zirconium species evenly in silica support.Thus,the interaction between copper and zirconia is significantly enhanced,resulting in more Cu-ZrO₂ interface species and effectively inhibiting the migration and agglomeration of Cu nanoparticles on the surface of the catalyst.Finally,the catalytic performance of the catalyst was prominently improved.Based on the above achievement that hydrolysis precipitation method can improve the catalytic performance of CuZr/SiO₂ catalyst,a series of CuZrx/SiO₂ catalysts with different amounts of ZrO₂ dopant were prepared by hydrolysis precipitation method.Combined with the characterization results of the catalysts,the structure-activity relationship of CuZr/SiO₂ catalyst in the hydrogenation of dimethyl oxalate to ethylene glycol was studied.The results showed that proper introduction of zirconia is beneficial to improve the copper dispersion on the catalyst surface and specific surface area of copper species（Cu⁰ and Cu⁺）,and effectively regulate the Cu⁺/（Cu⁺+Cu⁰）ratio.In comparison with the surface Cu⁺species formed by the reduction of copper phyllosilicates(Cu_2-xSi₂O₅（OH）₃·x H₂O),the unique Cu⁺sites originated from the Cu-ZrO₂ species have stronger ability in adsorbing the intermediate-methyl glycolate（MG）of DMO hydrogenation.Thus,the synergistic effect between the active sites of Cu⁺and Cu⁰ is significantly enhanced,which is notably conducive to the formation of the target product-EG.Among them,the TOF normalized by Cu⁰ on CuZr1/SiO₂ catalyst is 1.8times of the traditional Cu/SiO₂ catalyst,showing a potential prospect in industrial application.