Structural investigation of zinc oxide clustering in zeolite A and sodalite
| Autor: | M. Wark, Michel Soulard, L. Khouchaf, Henri Kessler, M.H. Tuilier |
|---|---|
| Rok vydání: | 1998 |
| Předmět: |
X-ray absorption spectroscopy
Extended X-ray absorption fine structure chemistry.chemical_element General Chemistry Crystal structure Zinc Condensed Matter Physics law.invention chemistry.chemical_compound Crystallography chemistry Mechanics of Materials law X-ray crystallography Sodalite General Materials Science Calcination Zeolite Nuclear chemistry |
| Zdroj: | Microporous and Mesoporous Materials. 20:27-37 |
| ISSN: | 1387-1811 |
| DOI: | 10.1016/s1387-1811(97)00003-6 |
| Popis: | The formation of small zinc oxide clusters in fully Zn-exchanged LTA zeolite and partially Zn-exchanged sodalite submitted to appropriate thermal treatments was investigated by X-ray absorption spectroscopy at the Zn K-edge. The absence of extraneous ZnO or ZnAl 2 O 4 particles as well as the changes in the zeolite framework produced by thermal treatments was checked by X-ray diffraction as well as 29 Si and 27 Al MAS NMR. In all the samples, the Zn cations are tetracoordinated to oxygen. In fully Zn-exchanged zeolite A, the EXAFS spectra result from the contribution of inequivalent Zn 2+ cations belonging to clusters of different size located in either the sodalite cages or the α-cages. In partially Zn-exchanged sodalite, after calcination, the presence of aluminum belonging to the framework as second neighbors of Zn at 2.86 A is demonstrated, whereas Zn neighbors of Zn are moved away to 3.39 A instead of 3.24 A in crystalline ZnO. The results are consistent with the adsorption on the sodalite framework of clusters involving three Zn cations probably hydrolyzed and belonging cither to the same cage or to three adjacent cages. |
| Databáze: | OpenAIRE |
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