Preparation Of Cu, Fe-based Catalysts And Catalytic Decomposition Of N₂O

In recent years, the emissions of nitrous oxide (N2O) from industry processes increased year by year. N2O has a global warming potential (GWP) of310relative to that of CO2and a lifetime of120years. Therefore, it is strongly required to destruct the exhausted N2O. Catalytic decomposition of N2O to nitrogen and oxygen is an economical and practical method. Due to the co-presence of oxygen and water, the performance of catalysts resisting to oxidant and steam must be taken into consideration.In this thesis, a series of Cu and Fe composite oxides were prepared by co-precipitation method, and their catalytic activity for N2O decomposition under oxygen condition was investigated. The effect of catalyst preparation parameters such as composite oxide composition, calcination temperatures and surface additives on the activity was screened, and the catalysts were characterized by BET, XRD, H2-TPR, and XPS techniques. The conclusions are drawn as follows:(1) CuAl mixed oxides derived from hydrotalcite-like compounds exhibited high activity for N2O decomposition. In the case of K/CuAl catalyst, the optimal catalyst can be prepared by impregnation of K2CO3solution over CuAl mixed oxide with K/Cu of0.1and calcined at400℃. The K addition improved the activity, stability, and water resistance of catalysts.(2) MgFe mixed oxides derived from hydrotalcite-like compounds showed some activity for N2O decomposition reaction, and the optimal sample is the one with Mg/Fe atomic ratio of0.57.(3) In MxFei-xFe2O4(M=Mg, Zn) spinel mixed oxides, Mgo.6Feo.4Fe204-500and Zn0.8Fe0.2Fe2O4-400catalysts showed better catalytic performance than others; both the activity and stability of catalysts decreased in steam, which need further improvement. Catalytic activity of K modified MxFe1-xFe2O4(M=Mg, Zn) spinel compound oxides was reduced, and it is found a negative correlation between K loadings and catalytic activity, possibly because the additives covered the FeOx on the surface, inhibiting the reduction of FeOx and making the surface oxygen difficult to desorb, and also because the surface concentration of FeOx reduced, thereby reducing the activity of K modified catalyst.