The role of the electrostatic potential, electric field and electric field gradient on the acidity of AFI and CHA zeotypes
- 22 December 1999
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Physical Chemistry Chemical Physics
- Vol. 2 (1) , 177-185
- https://doi.org/10.1039/a907464c
Abstract
We consider the role of short- and long-range interactions in determining the acidity of microporous solids. Within the context of an interatomic forcefield approach and a correct treatment of long-range electrostatics we demonstrate the role of the electrostatic potential, electric field and electric field gradient in determining the vibrational frequency of a Brønsted acid centre. We demonstrate the applicability of these concepts for AlPO4-5, AlPO4-34, SSZ-24 and SSZ-13, in whose unit cells a single Brønsted acid site was introduced in the four different oxygens. Furthermore, we show, by using the energy required to elongate the OH bond—essentially the first stage of proton transfer—as a measure of acidity, how the vibrational frequency is related to the acid strength.Keywords
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