| Catalytic CO oxidation is important for both industrial application and fundamental research. It is currently a hot research topic to prepare low cost and high-performance catalysts for this reaction. In this thesis, the preparation and properties of non-noble metal catalysts with high activity, good stability and water resistance have been studied for low temperature CO oxidation. The physicochemical properties of the prepared catalysts were characterized by means of N2 adsorption-desorption, XRD, H2-TPR, SEM, XPS, TEM, ICP and FTIR, whose effects on the reaction performance of the catalysts were also investigated. The main results are summarized here:First, with a facile co-precipitation method, a series of high surface area mesoporous CuxSn1-xOy solid solution catalysts have been synthesized and applied to CO oxidation. The highest activity is achieved on Cu0.5Sn0.5Oy with Caramel-Treats-like morphology, which is also resistant to water vapour deactivation. As testified by N2 adsorption-desorption and SEM results, these CuxSn1-xOy catalysts contain well-defined mesopores and possess high surface areas and improved pore volumes. It is revealed by XRD that Cu2+ cations have been incorporated into the crystal lattice of rutile Sn O2 to form uniform solid solution structure. More active and loosely bounded oxygen species has been formed on the surface of these catalysts. It is believed that these are the predominant reasons leading to the superior CO oxidation activity over the CuxSn1-xOy catalysts. In addition, the influences of calcination temperatures, precipitation sequences and calcination atmospheres on the activity of the best catalyst were investigated, with the optimal conditions listed here: precipitated with inversed sequence; calcined in N2 atmosphere at 200 oC.Second, the mesoporous Cu-Sn nanorods were successfully fabricated with a KIT-6 hard template. The sample calcined in air atmosphere at 400 oC showed the highest activity for CO oxidation, which can oxidize CO completely at 130 oC. It is noted that this Cu-Sn nanorods’ activity is relatively higher than the above-mentioned nanosheets calcined at the same temperature. The nanorods have an average length of 500 nm and a diameter about 20 nm. Due to the presence of a large amount of mesopores around 4 nm, the surface area of this nanorods is high than that of the Cu-Sn nanosheets. It is revealed by XRD that Cu2+ cations have been incorporated into the crystal lattice of rutile SnO2 to form uniform solid solution. As a result, more active and loosely bounded oxygen species has been formed on the surface of the catalysts, thus improving the CO oxidation activity of the catalysts.Third, 15% Ag-Sn catalysts were prepared by different methods and calcined at 500 oC in air atmosphere. It is founded that the catalysts prepared by co-precipitation and hydrothermal methods show the highest activity, on which CO can be completely oxidized at 170 oC. Interestingly, for 15% Ag-Sn catalysts calcined at 300 oC, the one prepared with co-precipitation method shows evidently improved low temperature activity. Therefore, the Ag/Sn ratio effects on the CO oxidation activity of the catalysts prepared by co-precipitation methods were further studied. It is found that when the Ag content is less than 33%, it is present in the catalysts as Ag2 O. As a consequence, these catalysts have better low temperature activity, but the CO conversion increases with the reaction temperature slowly. In comparison, when the Ag content is above 33%, an additional Ag2O2 phase can be detected. Although these catalysts have relatively lower activity at low tempeatures, the CO conversion can light-off quickly to 100% in a very narrow temperature region, which is similar to the reaction behaviors of noble metals. |
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