Study On The Preparation Of Copper Based Catalyst With High Dispersion And High Stability And Its Performance In The Hydrogenation Of Dimethyl Oxalate To Ethylene Glycol

Ethylene glycol is a versatile platform compound that is widely used in the polyester industry and in the production of refrigerants and additives.With the continuous development of the industrial chain and the continuous development of downstream products,the demand for ethylene glycol in China is increasing year by year.Ethylene oxide hydration is the most mature ethylene glycol production process,the raw material of this process depends heavily on petrochemical industry.However,the energy distribution characteristics of"rich coal,poor oil and less gas"in our country make it impossible for our country to continuously produce ethylene glycol in large quantities.Therefore,the C1 chemical route with rich raw materials has attracted the attention of scholars and enterprises.At present,the process of"coal→syngas→dimethyl oxalate（DMO）→ethylene glycol"is fully integrated,while the deactivation of DMO hydrogenation catalyst has not been solved properly.In this paper,Cu/SiO₂ catalysts with larger specific surface area and higher dispersion of active species were prepared by optimized preparation conditions.The characterization results show that the pretreatment of catalyst precursor can effectively increase the specific surface area of the catalyst.The specific surface area of the catalyst is directly affected by the change of copper content.Cu Si₃ catalyst has a suitable copper content,and its specific surface area is reach up to 619.5 m²·g^-1.The results of N₂O,H₂-TPR,TEM,XPS and XAES showed that the copper particles on the pretreated catalyst were smaller and the dispersion was higher.After reduction,the catalyst showed high catalytic activity with a proper ratio of Cu⁺/Cu⁰ on the surface.Cu Si₃ catalyst achieve 93.03%ethylene glycol yield at a relatively mild temperature（200℃）and a very high liquid hour space velocity(1.6h^-1).For the sake of elevating the life-span of the catalysts,Based on Cu/SiO₂catalyst with high dispersion,a certain amount of nickel was doped into the catalyst.The characterization results showed that the nickel species could not be completely precipitated due to the limitation of the preparation system.,but the introduced nickel still played a role in stabilizing the copper species to a certain extent,and the catalyst life increased from less than 150h to more than 250h by doping appropriate amount of nickel on the catalyst.In view of the fact that nickel doping did not significantly improve the stability of the catalyst,the Cu/SiO₂ catalyst was modified with Co which share the similar cell parameters with copper.The characterization results showed that cobalt doping increased the pore volume,and the copper species on the catalyst had smaller particle size and higher dispersion.The highest EG yield of 94.12%was obtained by cobalt-doped catalyst under optimized reaction conditions.The introduction of cobalt improves the stability of the catalyst:the yield of 94%ethylene glycol can still be obtained after the catalyst 3%Co-Cu/SiO₂ operation at 180℃ for 600 h.