Behavior of Coprecipitated NiAl2P4/Al2O3 Catalysts for Low-Temperature Methane Steam Reforming

The suitability of the nickel aluminate phase as an effective precursor for producing highly active and stable Ni/alumina catalysts was investigated in the steam reforming of methane with a H2O/CH4 ratio of 3 in the 450-650 degrees C temperature range. Particularly, the effect of the preparation route, including dissolution followed by crystallization, coimpregnation, and coprecipitation, for obtaining either bulk or alumina-supported samples was analyzed. A special attention was paid to correlating the characteristics of the calcined catalytic precursors with a Ni content varying between 17 and 33 wt %, namely, textural properties, composition, nature, and relative abundance of the existing nickel phases (NiAl2O4 and NiO), as well as reducibility, with the Ni crystallite size, dispersion, and metallic surface area obtained after a severe high-temperature reduction step (850 degrees C). A high intrinsic activity was found for the coprecipitated catalysts. This route was also effective for increasing the available metallic surface area. The best reforming performance (with a methane conversion of 78-80% and yield of hydrogen close to 1.63 at 650 degrees C and 38 400 cm(3) CH4 g(-1) h(-1)) was achieved by a reduced alumina-supported (17 wt % Ni)NiAl2O4 catalyst and the bulk NiAl2O4 catalysts prepared by coprecipitation.