Department of Chemical and Biomolecular Engineering, Tulane University, 6823 St. Charles Avenue, New Orleans, LA 70118, USA.
The Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA 99164, USA.
Chemphyschem. 2023 Jul 3;24(13):e202300271. doi: 10.1002/cphc.202300271. Epub 2023 May 19.
The influence of the copper ion exchange protocol on SCR activity of SSZ-13 is quantified. Using the same parent SSZ-13 zeolite, four exchange protocols are used to assess how exchange protocol impacts metal uptake and SCR activity. Large differences in the SCR activity, nearly 30 percentage points at 160 °C at constant copper content, are observed for different exchange protocols implying that different exchange protocols lead to different copper species. Hydrogen temperature programmed reduction on selected samples and infrared spectroscopy of CO binding corroborates this conclusion as the reactivity at 160 °C correlates with the intensity of the IR band at 2162 cm . DFT-based calculations show that such an IR assignment is consistent with CO adsorbed on a Cu(I) cation within an eight-membered ring. This work shows that SCR activity can be influenced by the ion exchange process even when different protocols lead to the same metal loading. Perhaps most interesting, a protocol used to generate Cu-MOR for methane to methanol studies led to the most active catalyst both on a unit mass or unit mole copper basis. This points to a yet not recognized means to tailor catalyst activity as the open literature is silent on this issue.
定量研究了铜离子交换方案对 SSZ-13 的 SCR 活性的影响。使用相同的母体 SSZ-13 沸石，采用四种交换方案来评估交换方案如何影响金属摄取和 SCR 活性。不同交换方案得到的铜物种不同，导致 SCR 活性有很大差异，在相同铜含量下，在 160°C 时相差近 30 个百分点。这一结论得到了选定样品的氢气程序升温还原和 CO 结合的红外光谱的证实，因为在 160°C 时的反应性与 2162 cm-1 处的红外带强度相关。基于密度泛函理论的计算表明，这种红外分配与在八元环内的 Cu(I)阳离子上吸附的 CO 一致。这项工作表明，即使不同的方案导致相同的金属负载，离子交换过程也会影响 SCR 活性。也许最有趣的是，一种用于生成 Cu-MOR 以进行甲烷转化为甲醇研究的方案，在单位质量或单位摩尔铜的基础上，产生了最活跃的催化剂。这表明可以通过一种尚未被认识到的方法来调整催化剂的活性，因为公开文献对此问题保持沉默。
