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, hi gh-pressure experiments are described and discussed. Relationships bet ween the occurrence of aggregation-disaggregation reactions of Ir spec ies on a low-surface-area polycrystalline alpha-Al2O3 and the formatio n of gaseous reaction product have been defined. Reactions in which ca rbidic oxidic and carbonyl species are interconverted have been produc ed and their role in CO and CO2 hydrogenation is discussed. The result s are compared with those previously found for Rh on alpha-alumina.