Deactivation mechanism of Cu active sites in Cu/SSZ-13-Phosphorus poisoning and the effect of hydrothermal aging

Non-poisoned and P-poisoned Cu/SSZ-13 catalysts with different types of Cu sites, i.e., [Cu(OH)](+) and Cu2+, were investigated for NH3SCR. Phosphorus was found to interact more with [Cu(OH)](+) than Cu2+. Moreover, less phosphorus was required per Cu for poisoning in the samples with a high content of [Cu(OH)](+). We propose a phosphorus poisoning mechanism based on H-2-TPR and XPS: poisoning of one Cu2+ involved two P atoms, i.e., P2O5, but for [Cu(OH)](+) contamination, only one P atom (PO3- or PO43-) is needed. Furthermore, phosphorus poisoning resulted in a decline in NH3/NO oxidation and an improvement in SCR activity at high temperatures. Upon hydrothermal aging, [Cu(OH)](+) - phosphate/metaphosphate complexes were likely easier detached from the framework than the Cu2+-P2O5 species. This resulted in that the P-poisoned catalyst with high content [Cu(OH)](+) experienced more severe deactivation and dealumination than the non-poisoned catalyst. Additionally, Al-27-NMR suggested that the formation of AlPO4 has a linear relationship with [Cu(OH)](+)/Cu2+ ratios.