Key points are not available for this paper at this time.
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.
Silaghi et al. (Mon,) studied this question.