DRIFT AND MASS-SPECTROMETRIC EXPERIMENTS ON THE CHEMISTRY AND CATALYTIC PROPERTIES OF SMALL IR CLUSTERS AT THE SURFACES OF POLYCRYSTALLINE ALPHA-AL2O3

The DRIFT and mass spectra collected during eight high-temperature, high-pressure experiments are described and discussed. Relationships between the occurrence of aggregation-disaggregation reactions of Ir species on a low-surface-area polycrystalline alpha-Al2O3 and the formation of gaseous reaction product have been defined. Reactions in which carbidic oxidic and carbonyl species are interconverted have been produced and their role in CO and CO2 hydrogenation is discussed. The results are compared with those previously found for Rh on alpha-alumina.