Preparation Of Mesoporous CeO₂and Co₃O₄and Their Application In CO Catalytic Oxidation Reaction

CO is one of the major air pollutants and it is a colorless, odorless gas which can be emitted from a large number of sources. Its presence even in traces can cause the serious environmental and health problems. Thus, control of CO in the air has been an important area of research. Catalytic CO oxidation is a well established and commercially exploited technology for the abatement of CO. In this paper, mesoporous CeO2and Co3O4were prepared and their application in CO catalytic oxidation reaction was studied. The detailed contents were as follows:1. The effects of cerium precursors, impregnation times, the ratio between cerium precursor and SBA-15as well as the calcination temperature in the synthetic process of mesoporous CeO2using hard-template method on the structure and catalytic performance of the final catalyst were investigated. It could be concluded that CeO2prepared using Ce(NO3)3·6H2O as cerium precursors, with double impregnation, with the ratio of1.1:1and calcination temperature of550℃showed the best structure and catalytic activity for CO oxidation.2. Structure and catalytic properties for CO oxidation of Ag catalysts supported on mesoporous CeO2prepared by hard-template method (CeO2-HP) and surfactant-template method (CeO2-SP) were investigated. The experimental results revealed that mesoporous CeO2-HP was the preferable support as compared to mesoporous CeO2-SP for Ag/CeO2catalysts in CO oxidation. A100%CO conversion was achieved at65℃for Ag/CeO2-HP, while that for Ag/CeO2-SP was at150℃. The difference in the catalytic performance of the two Ag/CeO2catalysts was thought to be due to the combination of several factors:the structure of support, the dispersibility of silver species, Ag0/Ag+ratio and the interaction strength between Ag and mesoporous CeO2.3. In order to further develop the new catalyst for CO oxidation at low temperature, mesoporous Co3O4and Ag/Co3O4catalysts were prepared. Compared with the Ag/Co3O4catalyst prepared using impregnation method, the one prepared using one-pot method showed the better catalytic performance. The CO conversion at20℃on the former was only4.9%while that on the latter was100%. The Ag/Co3O4catalyst prepared using one-pot method also showed better catalytic performance for formaldehyde oxidation at low temperature (the formaldehyde conversion at90℃was95%). In addition, the different catalytic behaviors of mesoporous Co3O4and Ag/Co3O4catalysts for CO and formaldehyde oxidation reaction were also investigated. It was found that the surface area, the structure of Co3O4and the silver particle size could be responsible for the room-temperature CO oxidation activity. But for formaldehyde oxidation reaction, the addition of Ag could promote the ability of catalyst for formaldehyde adsorption and oxidation at low temperature and the difference in activity for the two Ag/Co3O4catalysts should be mainly related to silver particle size and the reducibility of Co3O4.