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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 H 2 O/CH 4 ratio of 3 in the 450−650°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 (NiAl 2 O 4 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°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°C and 38 400 cm 3 CH 4 g −1 h −1 ) was achieved by a reduced alumina-supported (17 wt % Ni)NiAl 2 O 4 catalyst and the bulk NiAl 2 O 4 catalysts prepared by coprecipitation.

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An electrodeposition process is used to synthesize nanotubes of a lanthanum-containing phase, employing porous alumina membranes as templates. This method should lead to the formation of La(OH)(3) nanowires, according to the previous results presented by Bocchetta et al (2007 Electrochem. Commun. 9 683-8), which can be decomposed to La(2)O(3), as the latter shows more interest for different applications. The results obtained by means of different electron microscopy techniques indicate that this method leads to the formation of nanotubes of about 200 nm in diameter and 30-40 µm in length, instead of the nanowires proposed in the literature. Additionally, the chemical characterization demonstrates that the material synthesized is composed of lanthanum hydroxycarbonate. The presence of carbonates is found to be crucial in determining the conditions for the preparation of La(2)O(3) from the nanotubes here obtained.

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