Superior performance in passive NOx adsorption over an Al-rich Beta zeolite supported palladium

Passive NOx adsorption (PNA) has been regarded as a new technology for NOx elimination at low temperatures in heavy diesel vehicles (HDV) during the cold-start period. For this process, it has been reported that zeolite-supported Pd samples are good adsorbents for the PNA, where the large pores and low Si/Al ratios (SAR) in the zeolites are favorable for the PNA. Therefore, we chose Al-rich Beta with both abundant Al species and large 12-membered ring pores as a support to load Pd species for preparation of the PNA adsorbents. As a result, 1 % Pd/Beta-4 showed much higher NO adsorption capacity than 1 % Pd/Beta-13, which is assigned to more Al pairs in the Beta-4 than those in the Beta-13. Even after hydrothermal treatment at 750 degrees C for 16 h, the 1 % Pd/Beta-4 still exhibited high passive NO capacity. These features should be helpful for the control of NOx emissions in the future.