Some surface chemical features of Pt catalysts supported on Al2O3 and CeO2/Al2O3

Pt catalysts supported on alumina and ceria-alumina have been investigated by the adsorption/coadsorption of CO, H2O, and H-2. Gas-volumetric and FTIR spectroscopic data indicate that, on pure alumina-supported systems, multiple-vacancy sites exist that tend to be eliminated in the presence of ceria; this is attributed to a strong Pt/CeO2 interaction. In the presence of large amounts of CeO2, the catalysts are active in oxidation processes also in reducing conditions. If the alumina component of the support of Pt-containing catalysts undergoes the thermal gamma --> delta,theta-Al2O3 phase transition, all the adsorptive capacity of Pt is lost.