Reaction of ethanol on oxidized and metallic cobalt surfaces

The reaction of ethanol on metallic and oxidized cobalt surfaces was studied using temperature programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS) in order to determine the dependence of the reaction pathways on the cobalt oxidation state. The primary reaction for ethoxide species on metallic cobalt surfaces was decarbonylation producing CO, H-2 and carbon. This reaction was facile and occurred below 400 K. In contrast. CoOx surfaces which predominantly contained Co2+ were selective for the dehydrogenation of ethoxide groups to produce acetaldehyde at 400 K. A fraction of the acetaldehyde molecules produced by this pathway were further oxidized to acetate which decomposed to produce CO2 at 495 K. More highly oxidized Co surfaces that contained both CO2+ and Co3+ were active for the complete oxidation of ethanol producing CO, CO2, and H2O as the primary products. The insights that these results provide for understanding the mechanism of the steam reforming of ethanol on cobalt catalysts is discussed. (C) 2010 Elsevier B.V. All rights reserved.