The Controllable Preparation Of CeO₂ Nanostructure Materials And Gold Loaded Catalysts For CO Oxidation

The chemical properties of rare earth element Ce is very different from other elements owing to its special electronic structure and larger atomic radius. Easy transformation between Ce3 + and Ce4 + caused to wide applications in polishing materials and catalysts. The preparation of rare earth nano-material has attracted more attention. And CeO₂ catalysts with special morphologies showed more application in nanomaterials due to the exposed special lattice faces. Especially one-dimensional CeO₂ nanostructure with larger BET specific surface area and oxygen storage capacity played more advantages. In present work, the synthesis of one-dimensional nano-structure CeO₂ and the influence of different reaction factors on the CO oxidation were performed, the main research contents are as follows:The precursor was synthesed using the same reactants, and one dimensional CeO₂ nanostructures were obtained by changing the subsequent reaction condition. It was found that the catalyst owing more surface oxygen exhibited better catalytic activity.Hydrothermal synthesis method and precipitation method were used to prepare CeO₂ nanorod and nanoparticles, respectively. The results exhibited that the catalytic activity of CO oxidation over CeO₂ nanorod was better, and calcination temperature showed strong influence on the CO oxidation. The activity of samples calcinated at 350 oC is better. CeO₂ nanoparticles was prepared by precipitation method, and it gradually grew to nanorods aging at 0°C. It is found that aging temperature was very important for morphology of the resulted samples.CeO₂ nanosphere was synthesized by hydrothermal method. Some factors was tested considering the influence of the concentration of reactants on catalytic activity and morphology. The uniform CeO₂ nanosphere is easy to form when the concentration of reactants is 3.125 M. It is found that the catalytic activity of all samples is near at low temperature, but CeO₂ nanosphere of uniform morphology has better catalytic activity when the temperature increase to 300 oC.In recent years, Au/ CeO₂ catalyst has attracted significant attention. The Au could activate surface oxygen of CeO₂, which led to greatly improvement catalytic activity. But the properties, particle size and morphology of support could influence the characters of Au / CeO₂ catalyst. A series of CeO₂ catalyst with different morphology were prepared in Teflon-linde stainless steel avtoclane. The CeO₂ nanorods exhibited the best activity. The conversion of CeO₂ nanorods is 100%, while conversion of CeO₂ nanocubes is 38% at 340 oC. After loading the same quality of Au on supports, all Au/ CeO₂ catalysts showed especially good activity. CeO₂ nanorods showed the best conversion and completely transformed at 340 oC.