Deactivation of Cu‐Exchanged Automotive‐Emission NH3‐SCR Catalysts Elucidated with Nanoscale Resolution Using Scanning Transmission X‐ray Microscopy. Issue 36 (28th February 2020)

• Record Type: Journal Article
• Authors: Ye, Xinwei; Schmidt, Joel E.; Wang, Ru‐Pan; van Ravenhorst, Ilse K.; Oord, Ramon; Chen, Tiehong; de Groot, Frank; Meirer, Florian; Weckhuysen, Bert M.
• Is Part Of: Angewandte Chemie international edition. Volume 59:Issue 36(2020)
• Page Start: 15610
• Page End: 15617
• Publication Date: 2020-02-28
• Subjects: automotive catalysis -- catalyst deactivation -- copper -- X-ray microscopy -- zeolites; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.201916554
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: To gain insight into the underlying mechanisms of catalyst durability for the selective catalytic reduction (SCR) of NO x 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 II to Cu I and Cu x O y 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 I 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 II sites trumps that of Brønsted acid sites for NH3 ‐SCR activity. Abstract : A look at the exhaust : The deactivation of NO x ‐reduction catalysts based on Cu‐exchanged SSZ‐13 and ZSM‐5 zeolites was studied by scanning transmissionX‐ray microscopy, which enables a spatial analysis of the local environment of both Al and Cu species at nanoscale resolution. The importance of isolated Cu species was shown and a correlation between zeolite lattice destruction and an inactive Cu phase was established.