Various activation conditions such as temperature, time and the concentration of H₂O during hydrothermal aging (HTA) treatment were extensively investigated to identify the proper ion-exchange conditions of Pd/SSZ-13 catalyst for low temperature NO adsorption performance. In addition, we examined how the cation in SSZ-13 (i.e. NH₄-, Na- or K-SSZ-13) affects the low temperature NO adsorption performance of Pd/SSZ-13 after HTA treatment. It is found that NO adsorption ability begins to increase substantially when Pd/SSZ-13 is hydrothermally aged above 650 °C. Pd/SSZ-13 demonstrated the maximum NO adsorption performance after hydrothermal aging treatment in the range of 700–750 °C, followed by the severe decline above 850 °C. Such deactivation is attributed to the agglomeration of Pd species due to the dealumination of SSZ-13, as indicated by XRD and NMR analysis. At least 15 h of HTA treatment at 750 °C is required to provide the optimum activation of Pd/SSZ-13. Water vapor is essential component to activate Pd/SSZ-13 during the hydrothermal aging treatment. Unlike NH₄-SSZ-13, Na- or K-SSZ-13 cannot be activated even if the optimum hydrothermal aging condition (750 °C for 25 h with 10% H₂O) is applied. EXAFS and XRD analysis provides the evidence about the sintering of Pd species of the Pd/Na- or Pd/K-SSZ-13 catalysts rather than Pd ion exchange, indicating that the pre-existing Na or K ion inhibits the ion exchange during hydrothermal aging treatment. It can be concluded that the selection of proper hydrothermal aging conditions and zeolite form is essentially required to obtain the excellent low temperature NO adsorption performance of Pd/SSZ-13 as a passive NOx adsorber.

广泛研究了各种活化条件，如温度，时间和水热老化（HTA）处理过程中H ₂ O的浓度，以确定Pd / SSZ-13催化剂对低温NO吸附性能的合适离子交换条件。此外，我们研究了SSZ-13中的阳离子（即NH ₄-，Na-或K-SSZ-13）影响HTA处理后Pd / SSZ-13的低温NO吸附性能。发现当Pd / SSZ-13在650℃以上水热老化时，NO吸附能力开始显着提高。Pd / SSZ-13在700-750°C的温度下经过水热老化处理后显示出最大的NO吸附性能，随后在850°C以上急剧下降。如XRD和NMR分析所示，这种失活归因于由于SSZ-13的脱铝而导致的Pd物质的团聚。为了使Pd / SSZ-13达到最佳活化状态，至少需要在750°C下进行15小时的HTA处理。在水热老化处理过程中，水蒸气是激活Pd / SSZ-13的必要成分。与NH ₄不同即使应用了最佳的水热老化条件（750°C，10％H ₂ O的条件下25小时），也无法激活-SSZ-13，Na-或K-SSZ-13 。EXAFS和XRD分析提供了有关Pd / Na-或Pd / K-SSZ-13催化剂中Pd物种烧结而不是Pd离子交换的证据，表明预先存在的Na或K离子会在水热过程中抑制离子交换时效处理。可以得出结论，为获得作为被动NOx吸附剂的Pd / SSZ-13优异的低温NO吸附性能，必须选择合适的水热老化条件和沸石形式。