Comparative study of H2 production by ethanol steam reforming on Ce2Zr1.5Co0.5O8-δ and Ce2Zr1.5Co0.47Rh0.07O8-δ:: Evidence of the Rh role on the deactivation process

The catalytic performance of Ce2Zr1.5Co0.5O8-delta and Ce2Zr1.5Co0.47Rh0.07O8-delta mixed oxides was evaluated comparing the influence of Rh insertion for hydrogen production in ethanol steam reforming. Rh doped and not doped catalysts were prepared by the pseudo sol-gel like method and were characterized using DRX, TPR, SEM, and TPO. For the Rh-doped catalyst, it was found an easier structure reducibility allowing to avoid a reducing activation treatment. The reactivity results show that lifetime of Ce2Zr1.5Co0.47Rh0.07O8-delta mixed oxide is more than 30 times higher, compared to the Ce2Zr1.5Co0.5O8-delta mixed oxide. Catalytic tests under various water/ethanol ratios and ethylene and acetaldehyde steam reforming evidence that the deactivation process for the catalytic systems is not only related to carbon deposits but also to carbonate species, which can be form from an acetaldehyde reaction sequence. The benefic effect of rhodium would ascribe to its ability to avoid carbonates formation under reaction, preventing the blocking of the active oxygen vacancies of the mixed oxide support. (C) 2008 Elsevier B.V. All rights reserved.