Operando HERFD-XANES/XES studies reveal differences in the activity of Fe-species in MFI and CHA structures for the standard selective catalytic reduction of NO with NH3
Operando HERFD-XANES/XES studies reveal differences in the activity of Fe-species in MFI and CHA structures for the standard selective catalytic reduction of NO with NH3
复制标题
操作性 HERFD-XANES/XES 研究揭示了 MFI 和 CHA 结构中的铁种在标准选择性催化还原 NO 与 NH3 时的活性差异
DOI：
10.1016/j.apcata.2018.11.026
复制
发表时间：
2019-01-25
影响因子：
5.5
通讯作者：
Beale, Andrew M.
中科院分区：
文献类型：
--
作者：
Agote-Aran, Miren;Lezcano-Gonzalez, Ines;Beale, Andrew M.
研究了含铁沸石作为标准NH3-SCR反应的催化剂，主要目的是了解这些材料的结构-功能关系。以H-ZSM-5、H-SSZ-13和硅石-1为载体，采用湿浸渍法合成了不同Fe核度（即分离种、团簇、大颗粒）的催化剂，并在NH3-SCR条件下采用原位x射线发射光谱（XES）和高能分辨荧光检测x射线吸收近边光谱（HERFDXANES）对催化剂进行了表征。这些技术的结合使我们对反应过程中发生的铁配位、氧化态和几何形状的变化有了详细的了解。结果表明，在研究条件下，H-ZSM-5上分离的八面体Fe3+具有高活性，暴露于NH3或SCR条件下会发生还原。相反，硅石-1中分离的四面体Fe3+位点表现出较低的氧化还原性质，导致NO转化减少。H-SSZ-13上的团簇和FexOy颗粒表现出较低的SCR活性。
Fe-containing zeolites were studied as catalysts for the standard NH3-SCR reaction with the primary aim of gaining insight into the structure-function relationship of these materials. Catalysts with different Fe nuclearity (i.e. isolated species, clusters, large particles) were synthesised by incipient wetness impregnation, using H-ZSM-5, H-SSZ-13 and Silicalite-1 as supports, and characterised by in situ and operando X-ray emission spectroscopy (XES) and high energy resolution fluorescence detected X-ray absorption near-edge spectroscopy (HERFDXANES) under NH3-SCR conditions. The combination of these techniques allowed us to obtain a detailed understanding of the changes in Fe coordination, oxidation state and geometry occurring during reaction. The results obtained suggested that isolated octahedral Fe3+ species on H-ZSM-5 are highly active under the conditions studied, undergoing reduction when exposed to NH3 or under SCR conditions. In contrast, isolated tetrahedral Fe3+ sites present in Silicalite-1 exhibited lower redox properties, leading to a reduced NO conversion. Clusters and FexOy particles on H-SSZ-13 exhibited low SCR activity.