Study On Preparation And Properties Of Catalysts Used For Selective Catalytic Reduction Of NO_x

NO_x, one of the main atmospheric pollutants, can cause great damages to human beings. In more than ten years, the effective reduction of NO_x has become one of the greatest challenges in the fields of global environmental protection and catalysis. Selective catalytic reduction (SCR) of NO_x by urea has a wide application background. However only a few zeolite based In, Pt, and Pd catalysts have been found to be active for this reaction, which are sensitive to the reduction conditions, meanwhile noble metals are now facing the crisis of resource scarcity. Therefore, in recent years, studies with transition metals have attracted much attention.In this thesis a series of corderite honeycomb supported CuO with different metal oxide were studied for the SCR of NO_x with CO(NH₂)₂ as reductant, and adopted the method of temperature progress to evaluate the SCR activity for all the catalysts conducted in the fixed-bed fluxion reactor. The catalysis samples were characterized by XRD, TPR, XPS and SEM techniques.The result showed that Cu-Ag-Co has higher activity in the range from 150℃to 350℃, and it makes the efficiency of the NO_x reduction exceed up to 80 percent. The research result indicates that catalytic activity relates with not only species of the active component but also the loaded quantity, GHSV and calcinate temperature. The catalytic activity also bears on the quality of carrier, the decentralization extent of active components, harmony performance among the active components. The addition of Ag and Co were advantageous to the reduction of NO_x.In the course of catalytic reductive reaction, Cu is in the form of CuO. Ag and Co can assort with carrier and active component to improve catalytic activity. The structures of Cu, Ag, Co before and after reaction don't change basically.Experimental results showed that Cu, Cu-Ce or Cu-Ag-Co can decrease the activation energy, remove reduction peak to lower temperature, increase the reaction rate, and improve the efficiency of NO_x reduction. Cu-Ag-Co stands out in the series.Mutual function between adsorption and desorption was studied according to N₂ adsorption-desorption isotherm. The data of BET surface area and average pore diameter by BET and BJH were acquired separately. The research result showed that the higher BET surface area and pore diameter, the more favorable for SCR NO_x with CO(NH₂)₂.