Research On Removal Of Propene And Carbon Monoxide Over Transition-metal-doped Ceria Catalysts

The automobile exhaust contains a lot of CO, CH, especially when the car is in the cold-start period. Cold-start emission problem can be resolved by lowering the ignition temperature of catalysts, reducing the ignition time and using pollutants capture-conversion technology. This paper focus on the catalytic activity of doping ceria with transition metals for C₃H₆ and CO oxidation, trying to get a low light-off temperature catalyst.Two series of Cu-Co-Ce-Zr and Mn-Co-Ce catalysts were prepared by co-precipitation and impregnation methods. The prepared catalysts were characterized by BET, BJH, XRD, H₂-TPR and Raman. The catalytic activities of the catalysts for low-temperature C₃H₆ and CO oxidation were evaluated through a microreactor-GC system.Diffractions presenting the cubic, fluorite type of CeO₂ are observed for most catalysts. This result may be due to the fine dispersion of transition metal oxides species or the formation of a solid solution. In Mn_0.8Co_0.2Ce₁, H₂-TPR results indicate that the synergetic interaction between copper and cobalt species would promote the reducibility of the catalyst. Doping ceria with transition metals Cu, Co, Mn by co-precipitation method have significantly improved physical and chemical properties, such as reducing the pore diameter, increasing the specific surface area and pore volume.Investigating the catalytic activity of transition metal oxides on the catalytic oxidation of C₃H₆ and CO, it comes to the conclusion: Co₃O₄>MnO_x>CuO. The activity and stability of complex oxide are usually better than that of single metal oxides, so we dope ceria with transition metals to improve the activities.In order to investigate the effect of CuO content on the performances of Cu-Ce-Zr catalysts, the activities of the Cu-Ce-Zr catalysts for low temperature C₃H₆ and CO oxidation were studied. The catalyst with the Cu/(Ce+Zr) atomic ratio of 1/4 is the most active among the studied catalysts. On this basis, partially substituting Cu with Co, Cu1-xCoxCZ catalyst were obtained. Results indicate that with the Co content gradually increasing, a gradual increase in the activity of C₃H₆ oxidation, but decrease in CO oxidation.The catalytic properties of the prepared Mn-Ce and Mn-Co-Ce catalysts with different atomic ratios were tested. Among Mn_xCe₁(x=0.33,1,3), Mn₁Ce₁ have the best activity. In series Mn_1-xCo_xCe₁(x=0,0.2,0.4,0.6,0.8,1), Mn_0.8Co_0.2Ce₁ is the best,temperature of 50% and 90% C₃H₆ conversion are 211℃and 260℃, and that of CO conversion are 128℃and 170℃, respectively。...