Carbon monoxide dissociation is the first step of cobalt-catalyzed Fischer-Tropsch synthesis, which converts syngas into high-purity hydrocarbons. It is thus of paramount importance to improve our understanding of this step for catalyst optimization.Here, monodisperse cobalt nanoparticles of 4, 10 and 15 nm diameters were exposed to CO and/or dihydrogen. The formation of new surface species and the changes in the surface oxidation state were investigated in-situ using a home-designed gas-cell operating under 1 bar and at temperatures up to 300C. X-ray absorption spectroscopy revealed a strong dependence of the dissociation kinetics on the nanoparticles diameter. Larger nanoparticles were shown to dissociate CO even at low temperature while smaller ones required heating and exposure to hydrogen.By showing unambiguously that �smaller is not necessarily better� in this size regime and by providing insights into the reaction mechanism, this work opens an avenue for a designing new catalysts for Fischer-Tropsch synthesis.

Size-effect of carbon monoxide dissociation with cobalt nanoparticles: An in-situ high-pressure XAS study

245th National Meeting (2013)

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