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Structure and Acidity Changes in Ultra-Stable Y Zeolites During Hydrothermal Aging: A Solid-State NMR Spectroscopy Study

Structure and acidity changes of the acid sites in ultra-stable Y zeolites of different cell sizes during the hydrothermal aging process were studied by solid-state nuclear magnetic resonance (NMR) combined with molecular probes. The experimental results demonstrated that, during the initial stage o...

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Bibliographic Details
Published in:Bopuxue zazhi 2020-03, Vol.37 (1), p.95-103
Main Authors: GAO Xiu-zhi, ZHANG Yi, WANG Xiu-mei, ZHANG Zhi-hua, XU Guang-tong
Format: Article
Language:Chinese
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Summary:Structure and acidity changes of the acid sites in ultra-stable Y zeolites of different cell sizes during the hydrothermal aging process were studied by solid-state nuclear magnetic resonance (NMR) combined with molecular probes. The experimental results demonstrated that, during the initial stage of hydrothermal aging, parts of the framework aluminum species were removed from the framework and formed five-coordinate extra-framework aluminum species. In the meanwhile, the five-coordinate extra-framework aluminum species migrated to the surface and formed poly-aluminum species, resulting in decreases of both Brønsted acid sites and Lewis acid sites. The acidity of ultra-stable Y zeolites changed considerably during the first 3 h of the aging process, and the change of Brønsted acid content was proportional to the unit cell dimension of the fresh zeolites agent. With the increase of aging time, the aluminum distribution tended to become stable, with little further changes in the amounts of Brønsted acid and Lew
ISSN:1000-4556
1000-4556
DOI:10.11938/cjmr20192745