Size-Dependent Activity and Selectivity of Fe/MCF-17 in the Catalytic Hydrogenation of Carbon Monoxide Using Fe(0) Nanoparticles as Precursors

Monodisperse Fe(0) nanoparticles with diameters between 1.8 and 9.0 nm were prepared from organometallic (Fe[N(SiMe3)(2)](2))(2) and intercalated into mesoporous MCF-17 silica. We observed high turnover frequencies of the catalytic CO hydrogenation; they increased with Fe particle size. Methane and short-chain olefin selectivities were highest for small particles, while the opposite trend applied to long-chain terminal olefins and oxygenates. The Anderson Schulz-Flory chain lengthening probabilities were found to increase with Fe particle size for both paraffins and terminal olefins. Reaction-induced sintering of the metal particles was limited and could be explained by the transformation of Fe(0) precursors into (mainly) Fe-carbides. The results cast new light on the structure sensitivity of the catalytic CO hydrogenation.