A DFT Study of the Acidity of Ultrastable Y Zeolite: Where Is the Brønsted/Lewis Acid Synergism?

The effect of extra‐framework aluminum (EFAL) species on the acidity of a HT6 cluster (T=Si, Al) was studied by density functional calculations. A higher acid strength, compared to an isolated site, was only found with Al(OH)2+. The increase in acid strength was not due to Brønsted/Lewis acid synerg...

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Bibliographic Details
Published in:Angewandte Chemie International Edition 2004-06, Vol.43 (23), p.3050-3053
Main Authors: Mota, Claudio J. A., Bhering, Daniel L., Rosenbach Jr, Nilton
Format: Article
Language:English
Subjects:
ab initio calculations
acidity
aluminum
Lewis acids
zeolites
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Summary:The effect of extra‐framework aluminum (EFAL) species on the acidity of a HT6 cluster (T=Si, Al) was studied by density functional calculations. A higher acid strength, compared to an isolated site, was only found with Al(OH)2+. The increase in acid strength was not due to Brønsted/Lewis acid synergism, as previously reported, but to the stabilization of the conjugated base through hydrogen bonding with the EFAL hydroxy groups (see picture).
ISSN:1433-7851
1521-3773
DOI:10.1002/anie.200353049