The interaction of NO with SO2-poisoned Cu-CHA deNOx catalysts

Cu-exchanged chabazite zeolites (Cu-CHA) are excellent catalysts for NOx removal from the exhaust gas of diesel vehicles, via the selective catalytic reduction of NO by NH3 to N2 and H2O (NH3-SCR). However, these catalysts deactivate upon exposure to SO2, that is formed from the sulfur-containing compounds in the diesel fuel. As we showed in our recent paper using XANES, EXAFS and XES data from BM23 and ID26, SO2 reacts predominantly with the [CuII2(NH3)4O2]2+ complex, and the other Cu-species in the NH3-SCR cycle remain virtually unaffected. To better understand the impact of SO2, it is important to look at the interaction between the catalyst and NO after exposure to SO2. In the proposed experiment we will reveal the influence of SO2 on the interaction between NO and Cu-CHA by monitoring the reaction of the [CuII2(NH3)4O2]2+ complex with NO in situ before and after exposure to SO2.