We have investigated the catalytic properties of size-selected subnanometer Co clusters (Co4Ox and Co27Ox) for oxidative dehydrogenation (ODH) of cyclohexane. The Cobalt cluster catalysts exhibit excellent activity at temperatures significantly lower than observed for conventional Pt and VOx catalysts. In situ X-ray absorption near-edge structure (XANES) and in situ Near Edge X-Ray Absorption Fine Structure (NEXAFS) measurements were performed to attain information on the evolution of oxidation state of cobalt during the reaction. To understand the observed low temperature activity of small Co clusters for cyclohexane oxidative dehydrogenation, we carried out DFT calculations on key steps for the reaction pathway. Combined with density functional studies, this work has shown that the high activity at low temperatures is due to the low binding energy between cyclohexene and the small clusters. Both theory and experiment lead to the conclusion that under-coordinated Co sites in small ConOm clusters are much more active for cyclohexane ODH.

Subnanometer cobalt clusters: Low temperature oxidative dehydrogenation catalysts

247th National Meeting (2014)

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