Deactivation of Pd/SSZ-13 passive NO_x adsorber from the perspectives of phosphorus poisoning and hydrothermal aging

Phosphorus is one of the typical derivatives that cause irreversible deactivation of passive NO_x adsorber (PNA). In this work, the deactivation effects of phosphorus on Pd/SSZ-13 were investigated in combination with hydrothermal aging treatment to gain deeper insights into phosphorus-induced deactivation. It was found that phosphorus decreased the porosity and acidity of Pd/SSZ-13 and the deactivation behavior mainly resulted from the decrease of active sites. Specifically, the isolated Pd sites (Pd²⁺ and [Pd(OH)]⁺) were poisoned by phosphorus species, leading to the transformation of isolated Pd sites to bulk PdO. After hydrothermal aging treatment, the phosphorus induced the extensive formation of AlPO₄ that significantly accelerated the dealumination of zeolite framework, thus resulting in the decrease in activity and stability. Our work sheds light on the deactivation mechanism of Pd/SSZ-13 from the perspectives of phosphorus poisoning and hydrothermal aging, expecting to provide guidance on the design of Pd-based zeolites with high tolerance and high stability for cold-start application.