CO HYDROGENATION ON MO-PROMOTED RH/SIO2 AND RH/ZRO2 DERIVED FROM METAL-CARBONYL CLUSTERS

Support and promoter effects on molybdenum-containing Rh/SiO2 and Rh/ZrO2 catalytsts, derived from the carbonyl precursors Rh4(CO)12 and Mo(CO)6, have been studied in carbon monoxide hydrogenation at 1.1 MPa. Mo increases the total activity of the catalysts. ZrO2 favours the formation of oxygenates, particularly ethanol. In situ FT-IR spectroscopic experiments, temperature-programmed reaction of adsorbed CO, H-2 and CO chemisorption, CO disproportionation as well as ethylene hydroformylation have been used to characterize the catalysts. Whereas the activity-promoting effect of Mo has been found to be due to the specific promotion of CO dissociation by Mo, the effect Of ZrO2 on the selectivity can be related to an increased CO insertion ability on zirconia-supported catalysts owing to the presence of activated surface carbonyl complexes, such as [GRAPHICS](~)under reaction conditions.