科研之友
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摘要
The water-induced formation of cobalt oxides by the re-oxidation of metallic cobalt in pre-reduced 10% Co/CeO(2)-ZrO(2) catalyst was verified by in situ temperature-programmed reduction (TPR) and in situ X-ray Photoelectron Spectroscopy (XPS) studies under various ethanol-steam conditions at 450 degrees C. The formation and transformation of water-induced cobalt oxide species during the reaction were influenced by the pre-reduction conditions as well as the feed stream composition. Our results suggest that the surface composition of the cobalt species (e.g. Co, CoO, and CoO(x)) in the 10% Co/CeO(2)-ZrO(2) catalyst, initially determined by the catalyst pre-treatment conditions, changed toward an equilibrium state governed by the feed stream composition as the reaction proceeded. In addition, the reducibility of the ceria sites may play a significant role in the formation of such water-induced cobalt oxide species, as the redox process involves both cobalt and ceria sites in the ethanol-steam environment. Finally, the effect of the water-induced cobalt oxides in the 10% Co/CeO(2)-ZrO(2) catalyst was investigated under ethanol and ethanol-steam conditions, particularly for the carbon-carbon (C-C) bond cleavage of ethanol. The water-induced formation of cobalt oxides in the catalyst was not observed to affect the cleavage, in either ethanol-rich (e.g. ethanol decomposition) or steam-rich (e.g. ethanol steam reforming) conditions. This result could be explained by our in situ studies, which revealed the redox exchange between reduced cobalt and oxidized cobalt in a feed stream with a changing water-to-ethanol ratio. Published by Elsevier Inc.
- 出版日期2010-7-28
