Properties and behavior of protonated boron-containing zeolites at different hydration degree have been investigated by means of periodic DFT approaches. Geometry optimization and room-temperature Car-Parrinello molecular dynamics results, in line with experimental findings, indicate that the BO3-bound silanolic acid site typical of dry boralites should convert to a solvated H3O+ hydrogen bonded to tetrahedral BO4 at moderate water content. By increasing the water loading, the tetrahedral structure of the B site is stabilized and the physicochemical properties of the water molecules solvating the acid proton gradually approach the liquid-phase ones. A relevant role of structural and vibrational properties of the zeolite framework in the water-induced trigonal-to-tetrahedral transition at the B site is highlighted by simulation results.

Water in acid boralites: Hydration effects on framework B sites

TABACCHI, GLORIA;GAMBA, ALDO;FOIS, ETTORE SILVESTRO
2008-01-01

Abstract

Properties and behavior of protonated boron-containing zeolites at different hydration degree have been investigated by means of periodic DFT approaches. Geometry optimization and room-temperature Car-Parrinello molecular dynamics results, in line with experimental findings, indicate that the BO3-bound silanolic acid site typical of dry boralites should convert to a solvated H3O+ hydrogen bonded to tetrahedral BO4 at moderate water content. By increasing the water loading, the tetrahedral structure of the B site is stabilized and the physicochemical properties of the water molecules solvating the acid proton gradually approach the liquid-phase ones. A relevant role of structural and vibrational properties of the zeolite framework in the water-induced trigonal-to-tetrahedral transition at the B site is highlighted by simulation results.
2008
dft calculations; first principles molecular dynamics; hydration; zeolites; acid sites; boron zeolites; bronsted acidity; acid catalysis
Trudu, F; Tabacchi, Gloria; Gamba, Aldo; Fois, ETTORE SILVESTRO
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11383/1707812
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