Partial oxidation of methane over Rh/supported-ceria catalysts: Effect of catalyst reducibility and redox cycles

Partial oxidation of methane (POM) was studied over Rh/(Ce_0.56Zr_0.44)O_2−x, Rh/(Ce_0.91Gd_0.09)O_2−x, Rh/(Ce_0.71Gd_0.29)O_2−x and Rh/(Ce_0.88La_0.12)O_2−x. The effect of catalyst reducibility and redox cycles was investigated. It was found that the type of doped-ceria support and its reducibility played an important role in catalyst activity. It was also observed that redox cycles had a positive influence on H₂ production, which was enhanced as the number of redox cycle increased. Results of carbon formation are discussed as a function of ionic conductivity. Temperature programmed reduction (TPR) profiles, BET surface area, ionic conductivity and XRD patterns were determined to characterize catalysts. Catalytic tests revealed that of the materials tested, Rh/(Ce_0.56Zr_0.44)O_2−x was the most active material for the production of syngas, which correlates with its TPR profile. It was observed that doping CeO₂ with Zr, rather than with La or Gd caused an enhanced reducibility of Rh/supported-ceria catalysts.