(216a) so2 Interactions with Pt, Pd, and Pd-Pt/Al2O3 Catalysts

Typical natural gas engine exhaust will contain uncombusted CH₄ that will need to be oxidized. Due to their high catalytic activity for the complete oxidation of methane, Pd-based catalysts are the typical choice for such oxidation systems. These catalysts can be exposed to trace amounts of sulfur compounds present in the engine exhaust. This sulfur exposure can lead to degradation in activity. The focus of this study was how sulfur interacts with Pd-based oxidation catalysts, as well as bimetallic Pt/Pd systems since Pt has been shown to have some resistance to sulfur poisoning. Temperature programmed desorption and oxidation were used to probe these interactions, as was DRIFTS to characterize surface species. The results show that the temperature, at which sulfur species are desorbed from sulfur-treated, mono and bimetallic Pd and Pt/Al₂O₃ catalysts, is dependent on the Pd-to-Pt mole ratio of the catalyst as well as the precious metal-crystallite particle size.