Pd-based small-pore zeolites with different framework structures (AEI, CHA and RTH) were synthesized by a facile incipient wetness impregnation method. The zeolites were utilized as low-temperature passive NO_x adsorbers (PNA) for NO_x storage before and after hydrothermal aging. It was found that 1 wt% Pd/AEI showed better PNA behavior than the 1 wt% Pd/CHA and Pd/RTH samples, regardless of hydrothermal aging at 750 and 800 ℃. The AEI zeolite has a three-dimensional but tortuous pore channel structure, which accelerated Pd dispersion at 750 ℃ but inhibited Pd aggregation at 800 ℃ when subjected to hydrothermal aging. Pd/CHA showed a slight increase in Pd dispersion at 750 ℃, but extensive Pd aggregation at 800 ℃ due to its straight and unhindered three-dimensional pore structure. The Pd species in Pd/RTH zeolite were prone to accumulation during hydrothermal aging due to the two-dimensional pore structure. Therefore, Pd/AEI can be utilized as an efficient and stable PNA after activation by mild hydrothermal aging treatment.

通过简便的初湿浸渍法合成了具有不同骨架结构（AEI，CHA和RTH）的Pd基小孔沸石。沸石被用作低温被动NO _X吸附器（PNA），用于NO _X水热老化前后的储存。结果表明，无论在750和800℃下的水热老化如何，1 wt％的Pd / AEI均表现出比1 wt％的Pd / CHA和Pd / RTH更好的PNA行为。AEI沸石具有三维曲折的孔道结构，在水热老化条件下，加速了750℃下Pd的分散，但抑制了800℃下Pd的聚集。Pd / CHA在750℃时Pd分散度略有增加，但在800℃时Pd / CHA由于其平直无阻的三维孔结构而广泛聚集。由于二维孔隙结构，Pd / RTH沸石中的Pd物种在水热老化过程中易于积累。因此，通过温和的水热老化处理活化后，Pd / AEI可以用作有效和稳定的PNA。