Ru/Ni/MgAl2O4 catalysts for steam reforming of methane: effects of Ru content on self-activation property

The effects of Ru on the self-reducibility of Ru-doped Ni/MgAl2O4 catalysts, which do not need pre-reduction treatment with H-2, were investigated in the steam reforming of methane (SRM). The Ru-promoted Ni/MgAl2O4 catalysts with various amounts of Ru (0-0.5 wt%) were prepared by stepwise impregnation and co-impregnation methods using hydrotalcite-like MgAl2O4 support. For comparison, Ru/MgAl2O4 catalysts with the same amount of Ru were also prepared by the impregnation method. The catalysts were characterized by the N-2-sorption, XRD, H-2-TPR, H-2-chemisorption, and XPS methods. Ni/MgAl2O4 catalyst in the presence of even the trace amount of Ru (Ru content a parts per thousand yen0.05 wt%) showed higher conversion without pre-reduction as compared to Ru/MgAl2O4 catalysts in SRM under the same conditions. The self-activation of Ru-Ni/MgAl2O4 catalysts is mainly attributed to the spillover of hydrogen, which is produced on Ru at first and then reduces NiO species under reaction conditions. Besides, Ru doping makes the reduction of NiO easier. The stepwise impregnated Ru/Ni/MgAl2O4 catalyst produced superior performance as compared to co-impregnated Ru-Ni/MgAl2O4 catalyst for SRM.