H-mordenite deactivation during the SCR of NOx.: Adsorption and diffusion of probe molecules on fresh and deactivated catalysts

H-mordenites with various Si/Al ratios (5.9 - 16.9) have proved to be active for the SCR of NO with CH4 in the 400-600 degrees C temperature range. However, they suffered an irreversible deactivation after an incursion at 650 degrees C for 1 h under reaction stream, due to a dealumination process. While acid dealumination only affects the free exchange of gaseous molecules between the main channels and the side-pockets (as seen by Xe-129 NMR), the aluminum extracted from the lattice of the mordenite during the SCR of NOx at 650 degrees C (without water vapor in the feed) also hinders the diffusive transport along the main channels.