No abstract

Using a Neuro ECAT positron tomograph the Positron Emission computed Tomography (PET) has been utilized to image the catalytic oxidation of CO by using CO and CO2, labelled with short lived positron emitting nuclides. Studies were performed over highly dispersed ceria/γ‐alumina supported platinum and rhodium catalysts. With a mathematical model of the reaction kinetics, based on the elementary steps of the catalytic reaction and partially on literature surface science data, the effect of CeO2 promotion and the presence of NO were quantified in terms of the number of adsorption sites and adsorption equilibrium constants. Oxygen atoms of CO2 remain much longer in the catalyst bed than the carbon atoms, which is due to carbonate formation at the ceria surface and exchange of the oxygen atoms of these carbonate groups with the ceria lattice oxygen atoms. The heat of desorption of CO from the noble metal surface at low temperatures was found to be increased due to the presence of NO molecules at the surface. At higher temperatures NO dissociates, the adsorbed N and O atoms have a repulsive interaction with adsorbed CO molecules.