Preparation Of Cerium-based Catalyst And Its Catalytic Performance For CO Oxidation

Carbon monoxide（CO）is a toxic gaseous pollutant that is produced by the incomplete combustion of carbon-containing fuels.Most carbon monoxide emissions come from modern cars,especially as much as 80%of carbon monoxide is still emitted during the cold start phase of a car.Catalytic oxidation of carbon monoxide（CO）with energy-saving and environment-friendly characteristics has been the most widely used technology for CO emission control.Although noble metal catalysts have excellent catalytic properties,their high cost and low reserves limit their applications.The development of non-noble metal catalysts with high activity and low cost has become one of the current research hotspots.Ce in lanthanide rare earth elements has good valence-changing property,and its oxide CeO₂ has the function of storing and releasing oxygen,and also has excellent redox property,so it is easy to form oxygen vacancy,it has great application potential in catalysis and other fields.It is difficult to realize catalytic oxidation of CO in pure CeO₂ at low temperature.In this paper,CeO₂ was modified and prepared（loaded with CuO and doped with Co O_x）,and the effects of exposed crystal face,phase composition and specific surface area of the catalyst on the catalytic oxidation performance of CO were investigated by XRD,N₂ physical adsorption,SEM,TEM,HRTEM,XPS and H₂-TPR.The main research contents of this paper are as follows:（1）CeO₂ supports with different morphologies were prepared by hydrothermal method.Rod CeO₂,spherical CeO₂ and layered CeO₂ were prepared by controlling hydrothermal synthesis conditions.Then CuO was loaded by wet impregnation method,and the effect of the morphology of CeO₂ support in CuO/CeO₂ catalyst on the catalytic oxidation performance of CO was investigated.The results showed that the catalytic activity of the catalyst was significantly improved after loading CuO,and the specific surface area,reducibility,content of surface active species,and exposed main crystal planes of catalysts with different morphologies were different.It was found that the（200）and（220）crystal planes of CeO₂ support exhibit stronger catalytic activity for CO oxidation than the（111）crystal planes.（2）CuO/CeO₂ catalyst with large specific surface area was synthesized by CTAB-assisted hydrothermal method combined with the control method of catalyst crystal plane in Chapter one.The addition of additives not only exposes different crystal faces of the catalyst,but also increases the specific surface area of the catalyst.Through characterization and activity evaluation,the effects of CuO loading on the properties of the catalyst and its catalytic CO activity were systematically investigated.It was found that when the loading was9wt%,the catalyst could produce more lattice oxygen and provide more Cu⁺as the active site of CO adsorption,showing the best catalytic performance for CO.（3）On the basis of the above research,Co^x+-doped CeCo composite oxide support was prepared by CTAB-assisted hydrothermal method,and 9wt%CuO was loaded by wet impregnation method.The influence of doping element cobalt on the physical and chemical properties and catalytic performance of the catalyst was studied by different characterization methods,and the relationship between the properties of doping element and the interaction between the active component CuO and the support CeO₂ in the catalyst was established.In addition,when n（Ce）:n（Co）=10:2,the catalyst has the best catalytic activity for CO.At this time,the interaction between cobalt and cerium in the support is the strongest,and the redox synergy with the active component CuO is also the strongest.It promotes the formation of oxygen vacancies and provides more Cu⁺adsorption sites for CO,thus enhancing the low-temperature activity of catalytic CO oxidation.