Regioselectivity of Al–O Bond Hydrolysis during Zeolites Dealumination Unified by Brønsted–Evans–Polanyi Relationship

We determine the mechanism of the initiation of Al–O­(H) bond breaking for zeolitic structures mordenite (MOR), faujasite (FAU), MFI, and chabazite (CHA) with high Si/Al ratio occurring during dealumination. Periodic density functional theory calculations demonstrate that water adsorption on the Al...

Full description

Saved in:
Bibliographic Details
Published inACS catalysis Vol. 5; no. 1; pp. 11 - 15
Main Authors Silaghi, Marius-Christian, Chizallet, Céline, Petracovschi, Elena, Kerber, Torsten, Sauer, Joachim, Raybaud, Pascal
Format Journal Article
LanguageEnglish
Published American Chemical Society 02.01.2015
Subjects
water dissociation
pentahedral aluminum
zeolite
dealumination
Al−O bond activation
density functional theory
Online AccessGet full text

Cover

More Information
Summary:We determine the mechanism of the initiation of Al–O­(H) bond breaking for zeolitic structures mordenite (MOR), faujasite (FAU), MFI, and chabazite (CHA) with high Si/Al ratio occurring during dealumination. Periodic density functional theory calculations demonstrate that water adsorption on the Al atom takes place in anti position to the Brønsted acid site, via a penta- or tetra-coordinated Al species. A subsequent 1,2-dissociation of water on adjacent framework oxygen atoms leads to the first Al–O­(H) bond breaking (with activation energies of ∼76–125 kJ/mol). A Brønsted–Evans–Polanyi relationship to estimate transition states (TS) is established and opens the door to predictions of which crystallographic sites are able to initiate dealumination.
ISSN:2155-5435
2155-5435
DOI:10.1021/cs501474u