Elucidation of Adsorbate Structures and Interactions on Brønsted Acid Sites in H-ZSM-5 by Synchrotron X-ray Powder Diffraction

Microporous H‐ZSM‐5 containing one Brønsted acid site per asymmetric unit is deliberately chosen to host pyridine, methanol, and ammonia as guest molecules. By using new‐generation in situ synchrotron X‐ray powder diffraction combined with Rietveld refinement, the slight but significant alteration i...

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Bibliographic Details
Published in:Angewandte Chemie International Edition 2016-05, Vol.55 (20), p.5981-5984
Main Authors: Lo, Benedict T. W., Ye, Lin, Qu, Jin, Sun, Junliang, Zheng, Junlin, Kong, Dejing, Murray, Claire A., Tang, Chiu C., Tsang, Shik Chi Edman
Format: Article
Language:English
Subjects:
Acids
Adsorbates
Ammonia
Angles (geometry)
Brønsted acid sites
Catalysis
Diffraction
Molecular chains
Molecular interactions
Parameter modification
Powder
powder X-ray diffraction
Pyridines
Rietveld refinement
Zeolites
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Summary:Microporous H‐ZSM‐5 containing one Brønsted acid site per asymmetric unit is deliberately chosen to host pyridine, methanol, and ammonia as guest molecules. By using new‐generation in situ synchrotron X‐ray powder diffraction combined with Rietveld refinement, the slight but significant alteration in scattering parameters of framework atoms modified by the guest molecules enables the user to elucidate their adsorption geometries and interactions with the Brønsted acid sites in H‐ZSM‐5 in terms of atomic distances and angles within experimental errors. The conclusion, although demonstrated in the H‐ZSM‐5, is expected to be transferable to other zeolites. This approach provides a stepping stone towards the rational engineering of molecular interaction(s) with acid sites in zeolitic catalysis. Atomic positions and interactions between small adsorbate molecules and zeolite H‐ZSM‐5 are revealed in the confined zeolite channels by in situ synchrotron powder X‐ray diffraction combined with Rietveld refinement. In this study the periodical lattice of H‐ZSM‐5 (one Brønsted acid site per asymmetric unit) was used as a template for trapping molecules (e.g. pyridine; see picture).
ISSN:1433-7851
1521-3773
DOI:10.1002/anie.201600487