Catalytic combustion of methane over Pt and PdO-supported CeO2–ZrO2–Bi2O3/γ-Al2O3 catalysts

Catalytic combustion of methane was investigated on Pt and PdO-supported CeO2–ZrO2–Bi2O3/γ-Al2O3 catalysts prepared by a wet impregnation method in the presence of polyvinylpyrrolidone. The catalysts were characterized by X-ray fluorescence analysis, X-ray powder diffraction, X-ray photoelectron spectra, transmission electron microscopy, and BET specific surface area measurements. The Pt/CeO2–ZrO2–Bi2O3/γ-Al2O3 and PdO/CeO2–ZrO2–Bi2O3/γ-Al2O3 catalysts were selective for the total oxidation of methane into carbon dioxide and steam, and no by-products such as HCHO, CO, and H2 were obtained. The catalytic activities of the PdO/CeO2–ZrO2–Bi2O3/γ-Al2O3 catalysts were relatively higher than those of the Pt-supported catalysts, due to the facile re-oxidation of metallic Pd into PdO based on lattice oxygen supplied from the CeO2–ZrO2–Bi2O3 bulk. A decrease in the calcination temperature during the preparation process was found to be effective in enhancing the specific surface area of the catalysts, whereby particle agglomeration was inhibited. Optimization of the PdO amount and calcination temperature enabled complete oxidation of methane at temperatures as low as 320 °C on the 11.6 wt% PdO/CeO2–ZrO2–Bi2O3/γ-Al2O3 catalyst prepared at 400 °C.