Methane reforming with CO2 over Ni/ZrO2-CeO2 catalysts prepared by sol-gel

Ni/ZrO2 catalysts promoted with different amounts of CeO2 (0, 1, 8 and 20 wt.%) were prepared by the sol-gel method. The catalysts were characterized after calcination at 800 degreesC and after reaction of CH4 reforming with CO2. Rietveld analysis reveals that the tetragonal ZrO2 phase (t-ZrO2) present in the catalysts is stabilized by the CeO2, forming a solid solution, and avoiding transformation to the monoclinic phase (m-ZrO2). Ni2+ also competes with Ce4+ in the incorporation to t-ZrO2. The t-ZrO2 stability increases with CeO2 concentration. The catalyst activity is increased with the CeO2 content, although some degree of deactivation, due mainly to the sintering of the support, was not completely avoided by ceria addition. The deposition of graphitic carbon does not play an important role in the catalysts deactivation. The catalytic performance is related to the Ni surface dispersion and NiO reducibility, both promoted by CeO2 incorporation. CeO2 enhances the reverse water-gas shift reaction during dry reforming of methane over the studied catalysts. (C) 2000 Elsevier Science B.V. All rights reserved.