Oxidative steam reforming of methane over Ni/α-Al₂O₃ modified with trace noble metals

Ni catalysts supported on α-Al₂O₃ modified with small amounts of noble metals (Pd, Pt, Au, Ir, Rh and Ru) were prepared by a co-impregnation method to investigate catalytic performance and catalyst bed temperature profile in oxidative steam reforming of methane. Modification of the Ni catalyst with noble metals was effective to decreasing the bed temperature near the catalyst bed inlet, and it is found that Pd is the most effective modifier among the noble metals. Additive effect of Pd has some aspects: the increase of the metal dispersion, suppression of oxidation and enhancement of reducibility judging from characterization results of H₂ adsorption and evaluation by pulse reaction technique using O₂ and H₂. The extended X-ray absorption fine structure (EXAFS) analysis suggests that the excellent properties can be due to small Pd metallic cluster interacted with Ni particles.