Preparation and Activity of Small Rhodium Metal Particles on Fishbone Carbon Nanofibres

A number of different impregnation and ion-exchange procedures have been employed to synthesize very small rhodium metal particles on HNO3/H2SO4-oxidized fishbone carbon nanofibres. The surface-oxidation of the nanofibres with HNO3/H2SO4 is a prerequisite for a good interaction between aqueous catalyst precursor solutions and the fibres. Depending upon the preparation technique applied and using 1 wt% rhodium metal loadings average particle sizes ranging from 1.1 to 2.1 nm were detected with XAFS spectroscopy. The rhodium metal particles are so small that metal–support interactions on carbon nanofibres can be investigated with XAFS spectroscopy. All catalysts are highly active in the liquid-phase hydrogenation of cyclohexene. No significant effect of particle size on the catalytic activity is observed, suggesting that other factors, such as clustering of the support particles in the liquid phase, are much more important.