Gold Catalysts Supported On Ceria Based Oxides For CO Catalytic Oxidation

CeO₂,due to the unique physical and chemical properties of its higher oxygen savings capacity,redox ability,cycling easily between reduced and oxidized states?Ce3+ and Ce4+?,has been applied in numerous reactions,such as the combustion of volatile organic compounds,water gas shift reaction,selective hydrogenation,alcohol selective oxidation and so on.Au/CeO₂ has been researched extensively due to its excellent activity for low-temperature CO oxidation.Au particle size,composition and structure as well as structure and property of the supports has a significant effect on the catalytic properties,such as particle size of the supports,morphology,feature of crystal face and so on.In recent years,some research works about the relations between cerium oxide morphology/crystal plane and Au catalyst activity were done in our group,some meaningful results have been obtained.It was found that the morphology of cerium oxidation has great influence on Au/CeO₂ redox ability and catalytic activity.CeO₂-rod and Au/CeO₂-rod showed better redox performance and higher catalytic activity due to its higher oxygen deficiency.It can be found that the introduction of metal impurity atoms have an effect on the feature of crystal plane.The dopping of Zr into ceria increase the proportion of reactive crystal planes {110} of CeO₂3 which can significantly improve the stability and catalytic activity of the supported gold catalyst.In this thesis,the structure,properties and catalytic activity of Au/Ce-M-O₂?M=Cu,Zr,Fe?for CO oxidation were discussed depending on the dopping of metal and morphology of supported.It was suggested that the structure of gold catalyst,chemical state,stability and catalytic activity depend on supports.Some interesting results are got as follows:1.On the basis of successful preparation of cerium oxide nanorods,nanocubes and nanopieces,a small amount of Cu was introduced into ceria lattice.The structure and redox properties of catalysts are studied systematically by XRD,TEM,TPR,solid UV-Vis,XPS,FTIR characterization techniques,it was found that:?1?In the CO catalytic oxidation reaction,gold catalysts supported CeO₂ nanorod shows higher catalytic activity,compared to the samples where CeO₂ pieces and CeO₂ cubes as support,due to exposed higher activite crystal faces?{110} {100}?,more oxygen defects and higher specific surface area.?2?The morphology of cerium oxide nanorods,nanocubes and nanopieces are not changed by the introduction of Cu.The function of Cu is related to the preparation methods,which lead to the difference in redox property and catalytic activity.1 wt%Au/Ce1-x-Cux-O₂ showed higher catalytic activity than corresponding 1 wt%Au?Cux/Ce1-x-O₂.Amount the catalysts,1 wt%Au/Ce1-x-Cux-O₂?x=0.03?showed the highest catalytic activity at room temperature?con%is higher than 50%?.2.A series of 1 wt%Au/Ce-Zr_0.02-O₂,1 wt%Au/Cei-x-Fex-O₂ with different morphology such as short rods,cubes and pieces were prepared,the effect of the material morphology and crystal plane features on their redox properties and catalytic activity were studied,it was found that the catalytic activity is related to the morphology of the support,short rods show the best catalytic activity.