Ye Xinwei, Schmidt Joel E, Wang Ru-Pan, van Ravenhorst Ilse K, Oord Ramon, Chen Tiehong, de Groot Frank, Meirer Florian, Weckhuysen Bert M
School of Materials Science and Engineering, Key Laboratory of Advanced Energy Materials Chemistry (MOE), Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Nankai University, Tianjin, 300350, P. R. China.
Inorganic Chemistry and Catalysis Group, Debye Institute for Nanomaterials Science, Utrecht University, Universiteitsweg 99, 3584, CG, Utrecht, Netherlands.
Angew Chem Int Ed Engl. 2020 Sep 1;59(36):15610-15617. doi: 10.1002/anie.201916554. Epub 2020 Feb 28.
To gain insight into the underlying mechanisms of catalyst durability for the selective catalytic reduction (SCR) of NO with an ammonia reductant, we employed scanning transmission X-ray microscopy (STXM) to study Cu-exchanged zeolites with the CHA and MFI framework structures before and after simulated 135 000-mile aging. X-ray absorption near-edge structure (XANES) measurements were performed at the Al K- and Cu L-edges. The local environment of framework Al, the oxidation state of Cu, and geometric changes were analyzed, showing a multi-factor-induced catalytic deactivation. In Cu-exchanged MFI, a transformation of Cu to Cu and Cu O was observed. We also found a spatial correlation between extra-framework Al and deactivated Cu species near the surface of the zeolite as well as a weak positive correlation between the amount of Cu and tri-coordinated Al. By inspecting both Al and Cu in fresh and aged Cu-exchanged zeolites, we conclude that the importance of the preservation of isolated Cu sites trumps that of Brønsted acid sites for NH -SCR activity.
为深入了解以氨为还原剂选择性催化还原（SCR）NO过程中催化剂耐久性的潜在机制，我们采用扫描透射X射线显微镜（STXM）研究了具有CHA和MFI骨架结构的铜交换沸石在模拟135000英里老化前后的情况。在Al K边和Cu L边进行了X射线吸收近边结构（XANES）测量。分析了骨架Al的局部环境、Cu的氧化态和几何变化，结果表明催化失活是由多种因素引起的。在铜交换的MFI中，观察到Cu向Cu和CuO的转变。我们还发现了骨架外Al与沸石表面附近失活的Cu物种之间的空间相关性，以及Cu含量与三配位Al之间的弱正相关性。通过检查新鲜和老化的铜交换沸石中的Al和Cu，我们得出结论，对于NH-SCR活性而言，保持孤立的Cu位点比布朗斯台德酸位点更为重要。
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