Promotional Role Of Zirconium On Cobaltosic Oxidecatalyst For Low-temperature Co Oxidation

The low-temperature catalytic oxidation of CO has attracted more and more attentions due to its widely used in exhaust purifying and other in practical aspect.The catalysts used in low temperature catalytic oxidation for CO comprise noble metal and transition metal series,in which precious metal catalysts show best performance,but are limited in widespread application because of their high cost,complicated preparation process,the deactivation induced by easy poisoning.Hence,it becomes the research focus to develop transition metal catalysts which are low cost but have the similar catalysts with noble metal catalysts.In the recent years,it has been found that Co3O4 has the high catalytic for CO oxidation,but is easy to deactivate in the presence of trace amount of water.Therefore,it is crucial for Co3O4 catalysts to improve its catalytic activity as well as catalytic stability.In the present work,Co3O4 catalysts promoted by ZrO2 are investigated,in which the catalysts were prepared by different methods to form the different interactions between cobalt component and zirconia.In order to.illustrate the effect of ZrO2 loading as well as the preparation methods of catalysts to CO oxidation,the activity of catalysts were tested at first,furthermore,its structure,physical properties and adsorption to CO and O2 were characterized using low-temperature N2 adsorption/desorption,TPR,O2-TPD,CO-TPD,in-situ DRIFTS,UV-vis and et al.Results show that ZrO2 promoter can increase the specific area of the catalyst,reduce the crystal size of catalyst,remarkably improve the catalytic activity and stability for the CO oxidation,in which-90 ? of the lowest temperature for CO fully conversion(T100)can be achieved.The characterization results of catalyst further show that the ZrO2 introduction not only promotes the adsorption and activation of O2 and CO,but also accelerates the formation and desorption of CO2 over catalyst,thus significantly enhances catalytic activity and stability.The structural characterization results of the catalysts also illustrate that ZrO2 can permeate into the crystal lattice of Co3O4 to form structural defects and crystal lattice distortion,lead to the activation as well as migration of lattice oxygen on the surfaces of catalyst and formation of a certain amount of oxygen vacancies.Furthermore,the formed oxygen species and the oxygen vacancies on the surface of the catalyst is considered as the catalytic active sites,which are depended on the introduction methods of ZrO2 promoter and the pretreatment conditions of catalyst.Compared with the catalytic activity of catalysts with different preparation methods,it can be found that catalysts prepared by the coprecipitation and fractional precipitation exhibit much higher activities than one with impregnation method,which might be ascribed to the higher dispersion of Co3O4 and ZrO2 in them.Among them,Co3O4/ZrO2 with 20 wt%ZrO2 loading prepared with the coprecipitation method shows the best performance for CO oxidation.