INFLUENCE OF SUBSTRATE STRUCTURE ON ACTIVITY OF ALUMINA-SUPPORTED PD PARTICLES - CO ADSORPTION AND OXIDATION

Recently the unexpected effects of partial CO dissociation were report ed for small Pd particles deposited on gamma-alumina, prepared by ther mal oxidation of aluminium whilst this behaviour was not observed on P d/alpha-alumina model catalysts. In this study we compared the CO adso rption and oxidation properties of Pd particles deposited on cc-alumin a substrates of different surface stoichiometry with those of Pd on ga mma-alumina. It was shown that the oxygen adsorption capacity as well as the reactivity of ct-alumina supported catalysts was lower than tho se of gamma-alumina supported catalysts. The CO and oxygen sticking pr obability measurements indicated the CO and O diffusion over the suppo rt that in the case of CO decreased with T. The temperature dependent CO oxidation rate was explained in terms of its limitation by the CO d iffusion process which is less important in the case of the aluminium rich alumina surface.