N2O decomposition over K-promoted NiAl mixed oxides derived from hydrotalcite-like compounds

NiAl mixed oxides derived from hydrotalcite-like compounds (HLCs) with Ni/Al molar ratio of 4.1 were incipiently impregnated by potassium carbonate solution to prepare K-promoted NiAl mixed oxide catalysts with K/Ni molar ratio in the range of 0.05 to 0.2, and applied in catalytic decomposition of N2O. The catalysts were characterized by ICP-AES, XRD, BET, H2-TPR, XPS techniques, and their catalytic activities for N2O decomposition were tested. The results show that the catalytic activity of NiAl mixed oxide impregnated by K2CO3 solution is much higher than that of NiAl mixed oxide without K species and superior to the catalyst prepared by fresh NiAl-HLC impregnated using K2CO3 solution. The effect of K loadings and calcination temperatures of catalysts on catalytic activity has been investigated. It is found that the catalytic activity of NiAl mixed oxide, especially the one with K/Ni=0.1 and calcinated at 400°C, is largely enhanced by the addition of K species in the presence of oxygen and/or steam. XPS and H2-TPR results show that the electron binding energy of surface active NiO species in K-promoted NiAl mixed oxides shifts to lower value, and the surface Ni-O bond is weakened, thus the reduction peak of surface NiO moves to lower temperature, and the catalytic activity is improved.