Study of the Co–Pt Synergism for the Selective Catalytic Reduction of NOx with CH4

The selective catalytic reduction of NOx with CH4 in excess oxygen with or without added water was conducted over a series of ion-exchanged mordenites. The fresh catalysts contained both Pt and Co cations in varying proportions. Different treatments of the solid either after or between exchanges were performed in order to learn about the beneficial effect of Pt added to Co-mordenite. Temperature-programmed reduction of the solids together with photoelectron spectroscopy provided information concerning the interaction, migration, and oxidation states of Co and Pt. These studies were performed over the fresh, reduced, and used catalysts. The best formulations have Co/Pt atomic ratios between 15 and 24 and they exhibit better water resistance than Co-mordenites.