Dry reforming of methane over Ni supported on doped CeO2: New insight on the role of dopants for CO2 activation

Abstract The role of dopants on the catalytic activity for the dry reforming of methane (DRM) was investigated on nickel supported on metal doped ceria (Me-DC) catalysts, Ni/Me 0.15 Ce 0.85 O 2-δ with Me = Zr 4+ , La 3+ or Sm 3+ , prepared by citric acid synthetic route. The catalytic activity was in the order Ni/Zr-DC 2 . After 50 h under stream at 800 °C, samples showed different amounts of filamentous carbon and the most promising catalysts in terms of low coke formation were Ni/Sm-DC and Ni/La-DC. The catalysts coking was not straightforward related to the Ni° particles size. Therefore, we analysed the role of dopants type in activating CO 2 , a step for coke oxidation. Redox and acid-basic properties of the supports surface have been studied by combining CO 2 splitting and CO 2 -TPD measurements. The amount of oxygen defects increased in the order into: La-DC≈Sm-DC > Zr-DC > CeO 2 . The extra oxygen vacancies introduced by La 3+ and Sm 3+ were not capable to split CO 2 . La-DC and Sm-DC showed significant differences in the numbers and strength of surface basic sites. Therefore, other phenomena rule the formation/removal of carbon on these catalysts. The nature of dopants influenced the Ni-supports interaction and the electronic state of the metal catalyst.