Collapse and recrystallization processes in zinc-exchanged zeolite-A: A combined x-ray diffraction, XAFS, and NMR study

L. M. Colyer, G. N. Greaves*, S. W. Carr, K. K. Fox

*Corresponding author for this work

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54 Citations (SciVal)

Abstract

The collapse and recrystallization of zinc-exchanged sodium zeolite-A has been observed in situ using combined X-ray spectroscopy and diffraction. The temperature at which this occurs is reduced by the presence of zinc, but the precipitation of NaAlSiO4 (nepheline) is blocked by the nucleation of ZnAl2O4 (gahnite), which persists to at least 1100°C. Within the hydrated zeolite phase zinc occupies disordered octahedral sites that become less disordered with calcination. When zeolite-A collapses, zinc adopts a tetrahedral but strongly disordered geometry, suggesting nonhomogeneity in the amorphous phase from which ZnAl2O4 precipitates. Combined X-ray methods have been complemented by solid-state 27Al and 29Si NMR, which have enabled estimates to be made of the extent of disorder in the starting zinc-exchanged zeolite-A structure as well as the degree of crystallinity in the gahnite aluminosilicate glass ceramic that develops after collapse.

Original languageEnglish
Pages (from-to)10105-10114
Number of pages10
JournalJournal of Physical Chemistry B
Volume101
Issue number48
DOIs
Publication statusPublished - 27 Nov 1997

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