Catalytic activity of alkali metal doped Cu-Al mixed oxides for N₂O decomposition in the presence of oxygen

Three CuAl hydrotalcite-like compounds (CuAl-HLc) with Cu/Al atomic ratio of 2.0, 3.1 and 4.1 were prepared by a co-precipitation method and calcined to convert into CuAl mixed oxides. The CuAl mixed oxide with Cu/Al atomic ratio of 3.1 was incipiently impregnated by alkali metal (Na, K, Cs) salt solution to prepare the modified CuAl mixed oxide catalysts. The properties of the catalysts were characterized by AES, XRD, FT-IR, BET, H₂-TPR and XPS techniques. The effect of CuAl mixed oxide compositions, alkali metal types and potassium precursors on catalytic activity for N₂O decomposition in the presence of oxygen were investigated. It is revealed that the catalytic activity of CuAl mixed oxides impregnated by K₂CO₃ solution is higher than that of Na₂CO₃ and Cs₂CO₃ doped catalysts. In addition,the catalytic activity of CuAl mixed oxides can be largely enhanced by the addition of K species from the precursors of K₂CO₃ and K₂C₂O₄, whereas KNO₃- and CH₃COOK-doped catalysts show a lower activity than sole CuAl oxide. The optimal K-doped catalyst exhibits a good activity for N₂O decomposition in the presence of oxygen and steam.