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Brønsted Acid Sites in Zeolites Characterized by Multinuclear Solid-State NMR Spectroscopy

 

作者: MICHAEL HUNGER,  

 

期刊: Catalysis Reviews  (Taylor Available online 1997)
卷期: Volume 39, issue 4  

页码: 345-393

 

ISSN:0161-4940

 

年代: 1997

 

DOI:10.1080/01614949708007100

 

出版商: Taylor & Francis Group

 

关键词: Zeolites;Brønsted acid sites;Bridging OH groups;Local structure;Solid-state NMR spectroscopy.

 

数据来源: Taylor

 

摘要:

Nearly all atoms contributing to the local structure of Brønsted acid sites in zeolites exhibit isotopes accessible for multinuclear solid-state nuclear magnetic resonance (NMR) investigations. Therefore, in the last 15 years, NMR spectroscopy has found numerous applications for the determination of the types of hydroxyl proton in zeolites, of their concentration, accessibility, and mobility, and for the characterization of their acid strength and local structure. It allows the study of the role of hydroxyl groups in the formation of adsorbate complexes and in heterogeneously catalyzed reactions. Meanwhile, NMR spectroscopy belongs to the most powerful techniques for the characterization of Brønsted acid sites in zeolites and related materials. The basis of this success is the invention of new sample preparation techniques, external magnetic fields with high-flux densities, effective line-narrowing methods, and new two-dimensional experiments, making the detection of highly resolved solid-state NMR spectra and the separation of spectral parameters possible. This article gives a review of these techniques and a summary of the most important applications of multinuclear solid-state NMR spectroscopy for the characterization of Brønsted acid sites in dehydrated zeolites.

 

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