CH4 Dissociation Mechanisms on Aged Three-Way Natural Gas Vehicle Pd/Al2O3 Catalyst

This paper deals with the kinetics of CH4 dissociation on a model Pd/Al2O3 catalyst. The adsorption and conversion of CH4 over reduced or oxidized catalysts were studied by applying a temporal analysis of products (TAP) reactor. The experiments are discussed in the light of a selected mechanism involving CH4 decomposition into carbon and hydrogen that cannot be simplified to a global reaction because of the importance of CH2 ad-species. This mechanism was modified for oxidized catalysts including steps for the formation of water involving the recombination of two neighbor OHads species. TAP experiments over the oxidized catalyst confirm the involvement of the metal/support interface, with a spill-over effect previously characterized on the reduced catalyst. Optimized kinetics parameters were compared to theoretical values showing a relatively good agreement.