A series of SiO2-supported MoO3, V2O5, and Pt catalysts were prepared for the study of model soot oxidation with simulated diesel exhaust gas. Composite samples of Pt with the metal oxides demonstrated higher oxidation activities than the single-component SiO2-supported MoO3, V2O5 or Pt catalysts in the absence of SO2 in the: reactant gas. Based on the effects of NO2 on carbon oxidation, a synergistic reaction mechanism was suggested to explain the effects of combining Pt with the oxides: Pt catalyzes the oxidation of NO with gas phase O-2 to NO2, while MoO3 and V2O5 catalyze the oxidation of carbon with NO2. Finally, the effects of SO2 on the carbon oxidation reaction were examined and discussed. (C) 2001 Elsevier Science B.V. All rights reserved.