The effects of Pt promotion on the oxi-reduction properties of alumina supported nickel catalysts for oxidative steam-reforming of methane: Temperature-resolved XAFS analysis Original Research Article

The effects of Pt trace addition on the oxi-reduction properties of the Ni/Al2O3 and Ni/La–Al2O3 catalysts during partial oxidation of methane (POM) and autothermal reforming of methane (ATR) were investigated. The xPt–Ni/yLa–Al2O3 catalysts containing 15 wt% of Ni, 0 or 12 wt% of La and 0 or 0.05 wt% of Pt were characterized by temperature-resolved X-ray absorption near edge structure (XANES) spectroscopy under various atmospheres. The in situ XANES analysis for Pt–Ni/Al2O3 under H2 and CO revealed that the presence of Pt sites can initiate the NiO reduction process by rapid dissociation of H2 and migration of atomic H to the NiO surface by hydrogen spillover. On the other hand, in situ XANES analysis under CH4 showed that the presence of Pt sites induces the activation of the methane, probably by initial dissociation of methane (CH4 → CH3 + H) followed by migration of atomic H to the NiO surface. In situ XANES experiments under a POM mixture demonstrate that Pt has an important role keeping Ni in the metallic state. The catalytic test results for POM and ATR demonstrate that Pt is an important promoter to maintain Ni in the metallic state at the inlet region of the catalytic bed, where CH4 and O2 coexist.