Unravelling the mechanism of lanthanum-enhanced Pd-SSZ-13 zeolite against phosphorus-poisoning for passive NOx adsorber

The integration of lubricant oil additives or biofuels compels the Passive NO x Adsorber (PNA) within automotive exhaust after-treatment systems to withstand chemical poisoning from contaminants such as phosphorus (P). For the first time, lanthanum (La) has been employed to enhance the operational efficacy of Pd-loaded small-pore SSZ-13 zeolite (i.e., Pd-SSZ-13) in the presence of phosphorus species. Our findings reveal that La modification significantly bolsters the resilience of Pd-SSZ-13 against P-induced deactivation during the cold-start phase. Furthermore, we have elucidated a pronounced reduction in the degradation of active cationic Pd 2 + ions and Brønsted acid sites within the Pd-SSZ-13 framework upon the introduction of La. Notably, La not only exerts a stabilizing influence on the framework aluminum at the Brønsted acid sites but also effectively mitigates the interaction between the active Pd 2+ species and phosphorus, thereby preventing the formation of metaphosphate and its subsequent conversion into bulk PdO x aggregates. This research offers profound insights, particularly concerning the utilization of La to augment the resistance of Pd-SSZ-13 zeolite catalysts against poisoning by various chemical poisons (such as alkali metals or sulfur) and to enhance their high-temperature hydrothermal stability.