Facile Synthesis And Studies Of CO Oxidation Over Ordered Ce-Based Catalysts

As we all know, CO oxidation is a very important topic in catalysis due to its important role in fundamental and practical applications. It has been reported in the literature that the synergy effect of support and mental oxide promotes the activity of catalysts for the CO oxidation. With the rise and development of porous materials, we tried to use the feature of porous materials like the high surface areas, large pore volumes, and high-quality pore structure on the traditional catalysts for CO oxidation. To make sure whether it can significantly improve the catalytic activity. At present, the most commonly employed catalysts include noble metal catalysts and non-noble metal catalysts. The CuO-CeO₂ catalysts have attracted much attention due to its excellent performances in CO oxidation. Noble metal catalysts have advantages of high activity, stability and long service life. Therefore, noble metal catalysts like Pd-based and Pt-based catalysts are widely applied in CO oxidation. In this paper,3DOM CuO-CeO₂ with wormhole-like mesoporous walls have been successfully fabricated by adopting highly ordered arrays of poly（methyl methacrylate）（PMMA） microspheres as the hard template and nonionic triblock copolymer （Pluronic P123） as the soft template. At the same time, PdO/meso-CeO₂ and meso-PdO-CeO₂ catalysts have been successfully fabricated by adopting highly ordered arrays of KIT-6 as the hard template. The physico-chemico properties of these catalysts were characterized by means of the techniques, such as X-ray diffraction （XRD）, Brunauer-Emmett-Teller （BET）, temperature-programmed reduction （TPR）, Raman technique and scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, X-ray photoelectron spectroscopy （XPS） and in-situ Fourier-transition infrared spectroscope. Combined with catalytic properties, a relationship between the catalyst structure and CO oxidation activities were established, as well as the porous materials’ effect on the CO oxidation activities. The main contents of the thesis are as follows:1. Three-dimensionally ordered macroporous CuO-CeO₂ catalysts were prepared using polymethyl methacrylate （PMMA） as a hard template and nonionic triblock copolymer （Pluronic P123） as the soft template. The effect of CuO loading and the 3DOM structure on CO oxidation activity were investigated. The results showed that the 20CuO-CeO₂-D has the best catalytic activity. Moreover, the catalytic activity is much better than the catalysts prepared using incipient-wetness impregnation method. This may be due to the better dispersion of CuO on CuO-CeO₂-D catalyst.2. PdO/meso-CeO₂ and meso-PdO-CeO₂ catalysts were prepared using KIT-6 as a hard template, and corresponding catalysts （PdO/CeO₂, PdO-CeO₂） were obtained by a sol-gel method. According to the data of activity, we know that the catalysts with mesoporous structure have the higher activity than the catalysts were prepared by a sol-gel method. The activity of PdO/meso-CeO₂ is higher than the meso-PdO-CeO₂, It shows that the free surface Pd and PdO species play an important role in CO oxidation, is not the Pdn+ in the Ce-Pd-O solid solution.