Ethylene hydroformylation on graphite nanofiber supported rhodium catalysts

We have investigated the effect of supporting rhodium on several different types of graphite nanofibers (GNFs) for the ethylene hydroformylation react ion at temperatures over the range 180-300 degreesC. The performance of the se systems was compared with that of a catalyst where the same metal loadin g was dispersed on silica. It was found that in general, while the activity of all the catalyst systems was similar, the GNF supported rhodium catalys ts exhibited a higher selectivity for the formation of propionaldehyde than the corresponding silica supported system. Furthermore, among the various rhodium/GNF catalysts, the ribbon type nanofibers appeared to give the high est selectivity to the desired product. The optimum temperature for the hyd roformylation reaction was found to be 240 degreesC, since at this conditio n one was able to achieve the combination of maximum activity with acceptab le selectivity. Based on many experiments in which the ratio of gaseous rea ctants was systematically varied it was evident that high partial pressures of CO and C2H4, and a concomitant low partial pressure of H-2 gave the opt imum performance. It is believed that the morphological characteristics: ac quired by rhodium when dispersed on the GNF edges is a critical factor rath er than the size of the individual crystallites. (C) 2001 Published by Else vier Science B.V.