Title : Kinetics in heterogeneous catalysis for DeNOx reactions : How to relate catalytic to surface properties
Kinetics for DeNOx reactions in three-way or lean conditions has been the subject of a huge number of investigations over mixed metal oxides and supported metallic catalysts, i.e., Platinum Group Metal. The complexity of these studies is usually related to the involvement of the support and especially the metal/support interface. According to the strength of such interactions, between nano-sized particles and the support materials, the size and the morphology of those metallic particles can be significantly altered inducing modifications in the kinetic behavior typically for structure-sensitive reactions. Some illustrations will be given through the kinetics of the reduction of NO to nitrogen in three-way near stoichiometric conditions and in lean conditions on mixed metal oxides showing the participation of different reaction intermediates. Correlations between kinetic parameters and surface properties will be tentatively established and discussed.
The second part will be dedicated to the role played by the metal/support interface visualized through Temporal Analysis of Products. Fresh and aged Natural Gas Vehicle Catalysts were analyzed from single methane and NO. Results will be discussed in order to identify the most prominent elementary steps governing the catalytic properties on fresh and aged samples.