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Influence of cation exchange on the Al-27-NMR spectra of zeolites

Masierak, W. and Emmler, T. and Buntkowsky, G. and Gutsze, A. (2003):
Influence of cation exchange on the Al-27-NMR spectra of zeolites.
In: Zeitschrift Fur Physikalische Chemie-International Journal of Research in Physical Chemistry & Chemical Physics, 217 (12), pp. 1613-1626. [Article]

Abstract

The influence of cation exchange on the Al-27-NMR spectra of NaA-zeolites has been studied by Al-27-MAS- and MQ-MAS-Solid State-NMR. From the Al-27-spectra a characterization of the different At sites in the A zeolites according to their chemical environment and the structural changes on the aluminosilicate network caused by the cation exchange are obtained. It is found that the exchange with cations with smaller ion-radius cause stronger distortions of the Al-27-NMR-spectra than exchange with larger cations like Ba2+. Employing MQ-MAS spectroscopy these distortions are revealed as second order quadrupolar effects for the smaller cations and as a combination of chemical shift and second order quadrupolar interaction for the Ba cation. These changes of the quadrupolar coupling are interpreted numerically via calculations of the lowering of the symmetry of the EFG tensor. Finally it is found that the exchange with divalent cations leads to distortions of the zeolitic framework and the formation of an extra-framework aluminum. To the best of our knowledge this is for the first time that evidence for the production of extra frame work aluminum by pure cation exchange without any thermal treatment has been found in type A zeolites.

Item Type: Article
Erschienen: 2003
Creators: Masierak, W. and Emmler, T. and Buntkowsky, G. and Gutsze, A.
Title: Influence of cation exchange on the Al-27-NMR spectra of zeolites
Language: English
Abstract:

The influence of cation exchange on the Al-27-NMR spectra of NaA-zeolites has been studied by Al-27-MAS- and MQ-MAS-Solid State-NMR. From the Al-27-spectra a characterization of the different At sites in the A zeolites according to their chemical environment and the structural changes on the aluminosilicate network caused by the cation exchange are obtained. It is found that the exchange with cations with smaller ion-radius cause stronger distortions of the Al-27-NMR-spectra than exchange with larger cations like Ba2+. Employing MQ-MAS spectroscopy these distortions are revealed as second order quadrupolar effects for the smaller cations and as a combination of chemical shift and second order quadrupolar interaction for the Ba cation. These changes of the quadrupolar coupling are interpreted numerically via calculations of the lowering of the symmetry of the EFG tensor. Finally it is found that the exchange with divalent cations leads to distortions of the zeolitic framework and the formation of an extra-framework aluminum. To the best of our knowledge this is for the first time that evidence for the production of extra frame work aluminum by pure cation exchange without any thermal treatment has been found in type A zeolites.

Journal or Publication Title: Zeitschrift Fur Physikalische Chemie-International Journal of Research in Physical Chemistry & Chemical Physics
Journal volume: 217
Number: 12
Uncontrolled Keywords: naa-zeolite al-27-mas-nmr quadrupol coupling constants nuclear magnetic-resonance solid-state nmr crystal-structure site preferences al complex li,na-chabazite aluminum absence forms naa
Divisions: 07 Department of Chemistry
07 Department of Chemistry > Physical Chemistry
Date Deposited: 27 Oct 2014 20:46
Official URL: http://apps.webofknowledge.com/full_record.do?product=WOS&se...
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756MX Times Cited:7 Cited References Count:32

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