Substitution clustering in a non-stoichiometric celsian synthesized by the thermal transformation of barium exchanged zeolite X
✍ Scribed by Nigel J. Clayden; Serena Esposito; Claudio Ferone; Michele Pansini
- Publisher
- Elsevier Science
- Year
- 2006
- Tongue
- English
- Weight
- 206 KB
- Volume
- 179
- Category
- Article
- ISSN
- 0022-4596
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✦ Synopsis
The thermal transformation of Ba exchanged zeolite X to celsian has been studied by 27 Al and 29 Si MAS NMR spectroscopy. Evidence for the degradation of the zeolite framework is present in the 29 Si NMR spectra after thermal treatment at 850 1C. Confirmation is provided by the 29 Si NMR data that synthesis of celsian via the decomposition of Ba exchanged zeolite leads to a single defect phase. Clustering of the isomorphous replacement of aluminium by silicon must occur to explain the observed 29 Si chemical shifts. The 27 Al NMR data show distorted aluminium co-ordination sites upon the thermal transformation of Ba exchanged zeolite X. The distortions present in the amorphous matrix are greater than those present in the monoclinic and hexagonal crystalline phases of celsian.