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Wet oxidation of ammonia was carried out in the presence of Ce-based composite oxide catalysts. Reaction proceeded rapidly in the high pH region, indicating that ammonia was more reactive than ammonium ion. The Co/Ce and /Ce composite oxides were remarkably active. The maximum percentage decrease in ammonia was attained at a Ce content around 20 mol % for Co/Ce and 20-50 mol % for /Ce, respectively. They exhibited high activity in the decomposition of hydrogen peroxide, which suggested that the high activity of these composite oxides in the oxidation of ammonia was due partly to their high redox property. It was found that their strong affinity toward ammonia also contributed to their high activity in the oxidation of ammonia. The ESR spectral analysis indicated that interactions between Co and Ce, and Mn and Ce, were present in these composite oxides. The activity of the /Ce catalysts was higher than that of water-soluble copper compounds which are known as the most active catalyst in the wet oxidation.

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The role of the V=O bond in V2O5 in the adsorption of several gases was studied by measuring the electron spin resonance (ESR) and the infrared (IR) spectra. The ESR spectra of V2O5 supported on γ-Al2O3 were similar to those of VOSO4 on γ-Al2O3. When such electron-donating gases as CO, SO2 and C2H4 were adsorbed on this V2O5-γ-Al2O3, the signal intensity of ESR increased and the splitting of the h.f.s. became clear. Upon treatment with an electron-accepting gas such as O2, a reverse change was observed. In the case of V2O5 supported on SiO2, similar ESR spectra were observed by the adsorption of CO after a mild reduction. The IR spectra of V2O5 have a sharp absorption peak at 1023 cm−1 due to the stretching vibration of the (V=O)3+ bond; this peak became broader by adsorption of such gases as CO and SO2. Simultaneously, the center of the peak shifted to the red region and a weak hump appeared at 980–990 cm−1, probably due to (V=O)2+. These results of the ESR and IR measurements reveal that these electron-donating gases are adsorbed on the (V=O)3+ bonds on the surface of V2O5, and that the increase in electron densities in the adsorption sites results from adsorption of these gases. Furthermore, the role of this (V=O)3+ bond in oxidation reaction was also discussed.

The catalytic activity of /Ce composite oxide in the wet oxidation of polyethylene glycol) and other organic compounds was investigated. The /Ce composite oxide had higher activity than either Co/Bi composite oxide or homogeneous copper catalyst. The catalyst had high redox property, and participation of a radical mechanism was suggested. The ESR and ESCA analyses indicated that the effect of Ce was to produce manganese species with lower valence states (Mn3+, Mn2+), and the combination of Mn4+ with Mn3+ or Mn2+ was assumed to be the cause of the high activity of the catalyst.