Novel nickel catalysts based on spinel-type mixed oxides for methane and propane steam reforming

Novel nickel catalysts based on magnesium aluminate spinel-type mixed oxides are developed as hydrocarbon reforming catalysts for hydrogen supply to polymer electrolyte fuel cells. The spinel catalysts were prepared by co-precipitation and the Pechini method, and the spinels prepared by the former method exhibited higher activity for methane steam reforming. The effect of spinel composition, Mg_1-xNi_xAl₂O₄ (x=0.17, 0.35, 0.50, 0.70, 1) was investigated on the activity and resistance to carbon deposition in steam reforming reaction. The turnover frequency for methane steam reforming at a steam-to-carbon (S/C) ratio of 2 increased with increase in the x value from 0.17 to 0.35, and then gradually decreased with further increase in the nickel content. The carbon deposition tolerance of the spinel catalysts was examined in propane steam reforming at S/C=1 and 600°C. The propane conversion during the reaction was ca. 98% over all catalysts tested, and the amount of deposited carbon, determined as carbon dioxide by temperature programmed oxidation, was least at x=0.17, which is 1/8 of that deposited on a conventional Ni/γ-Al₂O₃ catalyst. The spinels with x≤0.5 exhibited smaller amounts of carbon deposition, and thus superior tolerance to deactivation.