Pt/ZrO2 and Pt/Ce0.14Zr0.86O2 catalysts containing 0.5 and 1.5 wt.% Pt were studied in order to evaluate the effect of the support reducibility and metal dispersion on the catalyst stability for the partial oxidation and the combined partial oxidation and CO2 reforming of methane. The Pt/Ce0.14Zr0.86O2 catalysts proved to be more active, stable and selective than Pt/ZrO2 catalysts during the partial oxidation reaction. No increase in deactivation was observed when the CH4:O-2 feed ratio was increased from 2:1 to 4:1. In addition, no water formation was observed at the high CH4:O-2 ratios. The activity of the catalyst is dependent upon both the dispersion and the ability of the catalyst to resist carbon deposition. The addition of CO2 resulted in a decrease in the methane conversion and a decrease in the H-2/CO ratio for the Ce0.14Zr0.86O2 and ZrO2 supported catalysts. Small increases in the temperature of the bed have been recorded during the partial oxidation reaction. However, within a few minutes the temperature stabilizes below the furnace temperature providing indirect evidence for the combined combustion and reforming mechanisms previously proposed. The 1.5 wt.% Pt/CeZrO2 catalyst shows promise for the autothermal reforming reaction based on the stability during transient operation. (C) 2004 Elsevier B.V. All rights reserved.