Deactivation of Pd/SSZ-13 by Potassium and Water for Passive NO_x Adsorption

The passive NO_x adsorber (PNA) material has been considered an effective candidate for the control of NO_x from diesel exhaust during the engine cold start stage, and Pd/SSZ-13 attracts peoples’ attention mainly due to its superior hydrothermal stability and sulfur resistance. However, chemical poisoning tolerance of Pd/SSZ-13 is another key parameter to its practical application and future development. Herein, we prepared potassium-loaded Pd/SSZ-13 and evaluated the influence on NO_x adsorption ability. The characterization results revealed that the loading of potassium could not destruct the structure of SSZ-13 but impaired the BET surface area and pore structure through the sintering of Pd species to PdO. Meanwhile, the grown PdO phase restrained the NO_x adsorption ability and promoted the generation of NO₂ at high temperatures. Moreover, the presence of H₂O could also impair the NO_x adsorption ability due to the competitive adsorption between H₂O and NO_x. This work verifies that the design of Pd/SSZ-13 sample with stable Pd species and excellent hydrophobicity is significant for its further application under harsh conditions.