Oxygen Isotopic Exchange On Three-Way Catalysts: A Dynamic Kinetic Model

A time-resolved kinetic analysis has been developed for modeling experimental results of 18O/16O isotopic exchange over oxide-supported metal catalysts. Model is based on two very important points: 1) the parallel calculation of surface and bulk diffusion and 2) the implication of certain O species such as superoxides. This model is based on rate equations and includes several elementary processes: adsorption on the metal nanoclusters, reactions on the metal nanoclusters, desorption from the metal nanoclusters, surface and bulk diffusion on/in the oxide support and direct exchange with the gas phase. On the basis of this model a computer code was developed to determine the kinetic and thermodynamic parameters of the oxygen isotopic exchange reactions. The characteristics of a Rh/CeO2 and Pt/CexZr1-xO2 catalysts were examined in the temperature range between 200 °C and 450 °C