Study On Catalytic Decomposition Of High Concentration Nitrous Oxide

The catalytic decomposition of nitrous oxide has good prospects for spacecraft propulsion applications. The M_xCoi_1-xCo₂O₄ (M=Ni, Zn and Mg) spinel composite metallic oxide catalysts supported on γ-Al₂O₃ particles were prepared by impregnation method. The deoxidized Ru/Mg/Al hydrotalcite-like compounds catalysts supported on γ-Al₂O₃ particles were synthesized by codeposition method. The catalysis ability and the lifetime of the two types of catalysts on the catalytic decomposition of nitrous oxide were investigated. The structure of the two types of catalysts was characterized by means of TPR, XRD, BET and XPS.Spinel composite metallic oxide catalysts have high activity on the decomposition of nitrous oxide. The influence of the preparation conditions on the catalytic activity, such as, the mole ratio between the two metals, calcination temperature, calcination time and loading weight was investigated in this paper. The effect of space velocity and furnace temperature on catalytic activity was also studied. The lifetime of the catalysts was evaluated. The 25% loading-weight catalyst Ni_0.8Co_0.2Co₂O₄/γ-Al₂O₃ that was calcined 3h under 600°C had the best activity. The results showed that the high activity of the catalysts was attributed to the interaction of metallic oxides and the formation of spinel crystal that was dispersed on the catalyst surface. The main reason of catalyst deactivation should be the loss of Co on the surface of the catalyst.The best preparation condition of deoxidized hydrotalcite-like compounds catalysts prepareded by codeposition method is the mole proportion of the Ru/Mg/Al is 15/64/21 and calcined 10h under 650°C. The catalytic characteristics on N₂O decomposition with that catalyst were investigated and the lifetime of the catalyst was also accessed. The characterization of the fresh and deactivated catalysts suggested that the loss of Ru under high temperature should be the main reason of catalyst deactivation.