Catalytic oxidation of cyclohexane with ozone was carried out over alumina-supported manganese oxides at 295 K. The catalytic activities decreased steeply with time on stream, and then reached a steady state. At the steady state, the mole fractions Of CO2 and CO were 90 and 10%, respectively, with the carbon balance of around 50%. The decomposition ratio was estimated to be 8-10, independent of Mn loadings and support materials. Partially oxidized compounds including alcohols, ketones, acid anhydrides and carboxylic acids were formed on the catalyst surface. These compounds were decomposed by ozone feed. On the other hand, highly resistant species containing C=O, COO- and CH groups remained on the catalyst surface, which caused the gradual deactivation of the catalyst. The C=O groups were decomposed at relatively lower temperatures (< 473 K), while higher temperature (> 473 K) was necessary to decompose the COO- and CH groups. (c) 2005 Elsevier B.V. All rights reserved.