This study addresses the impact of SO₂ exposure on the catalytic performance of a Cu-chabazite-based SCR catalyst, as used in diesel exhausts, to reduce the emission of NOx through the NH₃-SCR reaction. The SCR activity is determined by a reaction of NO with the [Cu₂^II(NH₃)₄O₂]²⁺ intermediate. The same intermediate is also the most reactive Cu-species towards SO₂. We demonstrate here that the reaction with NO at 200 °C is limited after exposure of the [Cu₂^II(NH₃)₄O₂]²⁺ complex to SO₂ or SO₂/O₂. Heating the catalyst to 300 °C in NO restores the reaction, albeit at a significantly lower rate. The lower reactivity towards NO indicates that exposure of [Cu₂^II(NH₃)₄O₂]²⁺ to SO₂ induces changes in the chemistry of Cu in the catalyst. This implies that poisoning of Cu-chabazite catalysts by SO₂ is, at least in part, of the chemical nature, and may be not limited to the physical pore blocking.

中文翻译：

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用于脱除柴油机尾气中 NOx 的 Cu-CHA 基 SCR 催化剂 SO2 中毒的化学性质


本研究探讨了SO ₂暴露对柴油机尾气中使用的铜菱沸石基SCR 催化剂的催化性能的影响，以通过NH ₃ -SCR 反应减少NOx 的排放。 SCR活性通过NO与[Cu ₂ ^II (NH ₃ ) ₄ O ₂ ] ²⁺中间体的反应来确定。相同的中间体也是对SO ₂最具反应性的Cu物质。我们在此证明，[Cu ₂ ^II (NH ₃ ) ₄ O ₂ ] ²⁺络合物暴露于 SO ₂或 SO ₂ /O ₂后，在 200 °C 下与 NO 的反应受到限制。将催化剂在 NO 中加热至 300 °C 可以恢复反应，尽管速率明显较低。对NO的较低反应性表明[Cu ₂ ^II (NH ₃ ) ₄ O ₂ ] ²⁺暴露于SO ₂会引起催化剂中Cu化学性质的变化。 这意味着SO ₂对Cu-菱沸石催化剂的中毒至少部分是化学性质的，并且可能不限于物理孔堵塞。