不同沸石骨架上 NH3-SCR 过程中 N2O 的形成：骨架结构、铜种类和水的影响,Industrial & Engineering Chemistry Research

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不同沸石骨架上 NH3-SCR 过程中 N2O 的形成：骨架结构、铜种类和水的影响
Industrial & Engineering Chemistry Research ( IF 3.8 ) Pub Date : 2021-11-30 , DOI: 10.1021/acs.iecr.1c02732
Joonsoo Han ₁ , Aiyong Wang ₁ , Ghodsieh Isapour ₁ , Hanna Härelind ₁ , Magnus Skoglundh ₁ , Derek Creaser ₁ , Louise Olsson ₁

Affiliation

研究了铜功能化沸石，即 Cu/SSZ-13 (CHA)、Cu/ZSM-5 (MFI) 和 Cu/BEA (BEA)的 N ₂ O的形成特征，并与相应的沸石进行了比较以 H 形式作为参考，以阐明骨架结构、铜添加和水的影响。氢程序升温还原表明，与 MFI 和 BEA 相比，CHA 骨架具有更高浓度的 Cu ²⁺ (Z2Cu)。表征和催化剂活性结果突出表明，与 MFI 和 BEA 相比，CHA 具有有利于硝酸铵 (AN) 高形成的框架结构。此外，发现在 Cu 物种存在下促进了 AN 的形成和分解。相反，降低 N ₂在标准和快速 SCR 反应期间，从 Cu/CHA 中观察到 O 形成，这被认为是由于沸石笼内高度稳定的 AN。另一方面，由于 AN 分解，在加热过程中会释放大量 N ₂ O，这意味着 Cu/CHA 的 AN 稳定性有利有弊，在瞬态条件下可能会形成不受控制的 N ₂ O。此外，还发现了水的重要影响，其中水阻碍了 AN 的形成并增加了分解为 NO ₂而不是 N ₂ O的选择性。因此，在水存在下观察到较少的可用 AN 形成 N ₂ O。这也在快速 SCR 条件下观察到，其中所有 Cu/沸石都表现出较低的连续 N₂ O 在水的存在下形成。

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N2O Formation during NH3-SCR over Different Zeolite Frameworks: Effect of Framework Structure, Copper Species, and Water

The formation characteristics of N₂O were investigated with respect to copper-functionalized zeolites, i.e., Cu/SSZ-13 (CHA), Cu/ZSM-5 (MFI), and Cu/BEA (BEA) and compared with the corresponding zeolites in the H form as references to elucidate the effect of the framework structure, copper addition, and water. Temperature-programmed reduction with hydrogen showed that the CHA framework has a higher concentration of Cu²⁺ (Z2Cu) compared to MFI and BEA. The characterizations and catalyst activity results highlight that CHA has a framework structure that favors high formation of ammonium nitrate (AN) in comparison with MFI and BEA. Moreover, AN formation and decomposition were found to be promoted in the presence of Cu species. On the contrary, lower N₂O formation was observed from Cu/CHA during standard and fast SCR reactions, which is proposed to be due to highly stabilized AN inside the zeolite cages. On the other hand, significant amounts of N₂O were released during heating due to decomposition of AN, implying pros and cons of AN stability for Cu/CHA with possible uncontrolled N₂O formation during transient conditions. Additionally, important effects of water were found, where water hinders AN formation and increases the selectivity for decomposition to NO₂ instead of N₂O. Thus, less available AN forming N₂O was observed in the presence of water. This was also observed in fast SCR conditions where all Cu/zeolites exhibited lower continuous N₂O formation in the presence of water.

更新日期：2021-12-15

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