Toward the aluminum coordination in dealuminated mordenite and amorphous silica-alumina : A high resolution 27Al MAS and MQ mas NMR study
In: Microporous and mesoporous materials, Jg. 86 (2005), Heft 1-3, S. 31-37
academicJournal
- print, 31 ref
Zugriff:
27Al MAS and MQ MAS NMR spectroscopy were used to study the aluminum coordination in dealuminated mordenite. A 27Al MAS NMR signal ascribed to distorted tetrahedrally coordinated Al (DTetrAl) was detected. By comparison with amorphous silica-alumina and alumina materials, in which no such signal was seen, the presence of DTetrAl species could be a typical feature in crystalline zeolites after activation and dealumination. An ammonium-water solution treatment under pressure in an autoclave was introduced; besides realumination of the activated zeolite, this treatment can transform six- and five- coordinate Al species to a tetrahedral coordination state, both in dealuminated zeolites and in amorphous silica-alumina, but not in alumina. From these experimental results we suggest that: (i) amorphous silica-alumina is a better model for the extra-framework material in dealuminated zeolites than alumina; (ii) DTetrAl species, which are absent in thermally treated amorphous silica-alumina, might be regarded as transitional from the crystalline framework lattice state to the amorphous silica-alumina state during the process of dealumination.
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Toward the aluminum coordination in dealuminated mordenite and amorphous silica-alumina : A high resolution 27Al MAS and MQ mas NMR study
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Autor/in / Beteiligte Person: | CHEN, Tie-Hong ; HOUTHOOFD, Kristof ; GROBET, Piet J |
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Zeitschrift: | Microporous and mesoporous materials, Jg. 86 (2005), Heft 1-3, S. 31-37 |
Veröffentlichung: | Amsterdam: Elsevier, 2005 |
Medientyp: | academicJournal |
Umfang: | print, 31 ref |
ISSN: | 1387-1811 (print) |
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