The impacts of Pd poisoning to the activity, selectivity, and hydrothermal stability of Cu/SSZ-13 selective catalytic reduction (SCR) catalysts are reported. Pd lowers DeNOx efficiency of Cu/SSZ-13 via two mechanisms: (1) displacing SCR active sites in the form of isolated Pd-ions, and (2) catalyzing non-selective NH₃ oxidation in the form of PdO. The first mechanism works by the diffusion of isolated Pd-ions into chabazite cages to displace ZCu^IIOH SCR active species, and it occurs on Cu/SSZ-13 catalysts with and without external surface CuO clusters in similar fashion. In contrast, the second mechanism works differently with and without external surface CuO clusters. For Cu/SSZ-13 catalyst without external CuO clusters (i.e., primarily isolated Cu-ions), PdO leads to significant decrease of DeNOx efficiency at reaction temperatures above ∼400 °C due to its non-selective NH₃ oxidation activity at high temperatures. However, this poisoning effect becomes much less impactful on Cu/SSZ-13 catalyst containing CuO clusters. This is due to the formation of CuO-PdO solid solution via interactions between CuO and PdO, which reduces non-selective NH₃ oxidation potential. Furthermore, this solid solution formation even mitigates adverse effects caused by hydrothermal aging. Hence, the poisoning effects of Pd are closely related to Cu speciation and spatial distribution of a Cu/SSZ-13 catalyst. Finally, this study suggests a strategy in eliminating Pd poisoning, that is, the introduction of an oxide phase that effectively traps PdO but does not adversely influence SCR.

报道了 Pd 中毒对 Cu/SSZ-13 选择性催化还原 (SCR) 催化剂的活性、选择性和水热稳定性的影响。Pd 通过两种机制降低 Cu/SSZ-13 的脱硝效率：(1) 以孤立的 Pd 离子形式置换 SCR 活性位点，和 (2)以 PdO 形式催化非选择性 NH 3 氧化_。第一种机制通过将孤立的 Pd 离子扩散到菱沸石笼中来置换 ZCu ^IIOH SCR 活性物质，它以类似的方式出现在具有和不具有外表面 CuO 簇的 Cu/SSZ-13 催化剂上。相反，第二种机制在有和没有外表面 CuO 簇的情况下工作不同。对于没有外部 CuO 簇（即主要分离的 Cu 离子）的 Cu/SSZ-13 催化剂，PdO 由于其在高温下的非选择性 NH 3 氧化活性，导致反应温度高于～400 °C 时脱硝效率显着_降低. 然而，这种中毒效应对含有 CuO 簇的 Cu/SSZ-13 催化剂的影响要小得多。这是由于 CuO 和 PdO 相互作用形成 CuO-PdO 固溶体，减少了非选择性 NH ₃氧化电位。此外，这种固溶体的形成甚至减轻了由水热老化引起的不利影响。因此，Pd的中毒作用与Cu/SSZ-13催化剂的Cu形态和空间分布密切相关。最后，这项研究提出了一种消除 Pd 中毒的策略，即引入可有效捕获 PdO 但不会对 SCR 产生不利影响的氧化物相。