Catalytic Decomposition of N₂O over Co-M(M=La, Ce, Fe, Mn, Cu, Cr) Composite Oxide Catalysts

摘要

A series of Co-M (M=La, Ce, Fe, Mn, Cu, Cr) composite oxide catalysts were prepared by co-precipitation method and tested in catalytic decomposition of N2O. The results showed that Co-Ce composite oxide with Ce/Co molar ratio of 0.05 (CoCe0.05 catalyst) performed best in the N2O decomposition reaction. The presence of NO and O-2 in the feed affected the decomposition rate of N2O over CoCe0.05 by adsorption of nitrate or nitrite species on the active site. The XRD, BET, O-2-TPD, and H-2-TPR methods were used to characterize the Co-M mixed catalysts. The analysis results showed that the redox ability of the active site (Co2+) was very important for the decomposition of N2O over these catalysts. The surface decomposition of N2O was accompanied by the oxidation of Co2+ to Co3+, and the desorption of surface oxygen was accompanied by the reduction of Co3+ to Co2+. The addition of other transition metal oxides except CeO2 lowered the redox ability of Co3+/Co2+, and thus lowered the catalytic activities for the decomposition of N2O. In addition, the rate-determining step of the catalytic N2O decomposition was also influenced by the addition of various metal oxides.