3D Raman Spectroscopy of Large Zeolite ZSM‐5 Crystals. Issue 29 (2nd May 2019)

• Record Type: Journal Article
• Authors: Attila, Özgün; King, Helen E.; Meirer, Florian; Weckhuysen, Bert M.
• Is Part Of: Chemistry. Volume 25:Issue 29(2019)
• Page Start: 7158
• Page End: 7167
• Publication Date: 2019-05-02
• Subjects: aluminum zoning -- Raman spectroscopy -- steaming -- zeolite; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201805664
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: Hydrothermal treatment is a common method used to modify the physicochemical properties of zeolite‐based catalyst materials. It alters the number and type of acid sites through dealumination and increases molecular diffusion by mesopore formation. Steaming also reduces the structural integrity of zeolite frameworks. In this study, Raman microscopy has been used to map large zeolite ZSM‐5 crystals before and after steaming. 3D elemental maps of T−O (T: Al or Si) sites of the zeolite were obtained. The Raman active vibrational bands were determined, which are indicative of (non‐) framework Al, as well as of structural integrity. Zeolite steaming caused the introduction of additional heterogeneities within the zeolite framework. Al migration and the formation of extra‐framework Al species were observed. The described experiments demonstrate the capability of 3D Raman spectroscopy as a valuable tool to obtain information on the spatial distributions of framework elements as well as defects within a zeolite‐based material. Abstract : On the map : Raman spectroscopy has been used to visualize the elemental distribution of large zeolite ZSM‐5 crystals to gain insights in the modifications caused by a hydrothermal treatment. The 3D distribution of Al and Si inside the zeolite ZSM‐5 framework has been revealed before and after steaming. It was found that the steaming pretreatment promoted the formation of heterogeneities in the near‐surface zeolite regions, most probably via the extraction of framework Al.