Ab initio calculations of NMR parameters of highly coordinated oxygen sites in aluminosilicates

Article Abstract:

Delta(sub iso), C(sub Q), and n calculations are presented using the density functional theory-based GIPAW method for all silicon, aluminum and oxygen sites and for the 14 O[3] atoms, which are bonded to three Al or Si atoms in the andalusite, sillimanite, and kyanite polymorphs of SiAl2O5. Due to relatively similar electric field gradient and chemical shift values, it is difficult to distinguish the different tricoordinated oxygen atoms present in the structures (OSiAl2 and OAL3) from X-O-X (X=Si, Al) sites by (super 17)) NMR.

Density functionals, Density functional theory, Structure, Chemical properties

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Characterization of the acidic properties of mesoporous aluminosilicates synthesized from leached saponite with additional aluminum incorporation

Article Abstract:

An investigation on the acidic properties of hexagonal mesoporous aluminosilicates synthesized via a new successful short time synthesis route was carried out using leached saponite and low concentration of surfactant. The effect of an additional Al incorporation, utilizing different aluminum sources, on the acidic properties of the folded sheet materials derived from saponite is studied.

Chemical synthesis, Properties

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Proton transfer in hydrated microporous aluminosilicates: A (super 1)H NMR study of zeolite chabazite

Article Abstract:

The proton exchange in the hydrated zeolite chabazite and in its cation-substituted forms is studied by applying a NMR approach to in situ precise determination. This exchange is interpreted as the reversible proton-transfer reaction between water molecules and small amounts of the excess protons (de)localized on the bridging oxygen atoms of the zeolite framework.

Nuclear magnetic resonance spectroscopy, Charge transfer, NMR spectroscopy

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