Kinetic Modeling of the Metal/Support Interaction for CH₄ Reaction over Oxidized Pd/Al₂O₃

This paper deals with the kinetics of CH₄ dissociation on model Pd/Al₂O₃ catalysts. The adsorption and conversion of CH₄ over oxidized catalysts, fresh or aged, were studied with a temporal analysis of products (TAP) reactor. Single CH₄ pulse TAP experiments were performed on a stabilized surface. The experiments are discussed in the light of a selected mechanism involving CH₄ decomposition into CO₂ taking into account an interaction between the metallic active sites and the support. TAP experiments over the oxidized catalysts confirm the involvement of the metal/support interface, with a spill-over effect. Optimized kinetics parameters validate this interaction of OH species adsorbed on Pd sites with alumina, showing a relatively good agreement between experimental and calculated outlet gas composition. Both fresh and aged catalysts follow the chosen mechanism with the same kinetic constants at 400 °C only an alteration of the catalytic surface areas explain the loss of activity.