Aerosol-Assisted Metal Poisoning of Cu/SSZ-13 during NH3-SCR Operation

Cu/SSZ-13 is a benchmark catalyst for the selective catalytic reduction (SCR) of NOx with NH3 in diesel exhaust aftertreatment, but its activity can be severely impaired by alkali and alkaline-earth metal poisoning. Conventional impregnation of catalysts with such poisons involves introducing metal species prior to catalytic testing. This means that any poisoning that develops concurrently with catalyst operation is not captured. Here, we develop an aerosol-assisted, reaction-coupled poisoning platform that continuously delivers metal-containing aqueous aerosols to SCR catalysts under hydrated NH3-SCR conditions. At nearly identical K loadings, aerosol-assisted poisoning caused substantially greater deactivation of Cu/SSZ-13 than conventional impregnation of the catalyst, with a more pronounced activity loss after poisoning at 400 °C than at 200 °C. The enhanced deactivation was accompanied by a more spatially extensive K distribution, stronger perturbations of the zeolite framework, preferential alteration of 8-membered-ring-associated [Cu(OH)]+-Z species, spectroscopic signatures consistent with CuOx aggregation, and partial neutralization of Brønsted acid sites. Similar pathway- and temperature-dependent deactivation trends were observed for Na-, Mg-, and Ca-poisoned Cu/SSZ-13 and for K-poisoned V2O5-WO3/TiO2. These results establish aerosol-assisted poisoning as a controlled, accelerated approach for evaluating metal-induced deactivation of SCR catalysts under hydrated reaction conditions.