Solid-state sup 23 Na and sup 27 Al MAS NMR study of the dehydration of Na sub 2 Oter dot Al sub 2 O sub 3 ter dot 3H sub 2 O

• Published in: Journal of the American Chemical Society 1990-12, Vol.112:25
• Main Authors: Dec, S.F., Maciel, G.E., Fitzgerald, J.J.
• Format: Article
• Language: English
• Subjects: 360202 - Ceramics, Cermets, & Refractories- Structure & Phase Studies; 400201 - Chemical & Physicochemical Properties; ALKALI METAL COMPOUNDS; ALUMINIUM COMPOUNDS; ALUMINIUM OXIDES; ANISOTROPY; CHALCOGENIDES; CHEMICAL SHIFT; DEHYDRATION; HAMILTONIANS; HYDRATES; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; KINETICS; MAGNETIC RESONANCE; MATERIALS SCIENCE; MATHEMATICAL OPERATORS; MOLECULAR STRUCTURE; NUCLEAR MAGNETIC RESONANCE; OXIDES; OXYGEN COMPOUNDS; QUANTUM OPERATORS; REACTION KINETICS; RESONANCE; SODIUM COMPOUNDS; SODIUM OXIDES; TEMPERATURE RANGE; TEMPERATURE RANGE 0400-1000 K
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja00181a006

The dehydration of Na{sub 2}O{center dot}Al{sub 2}O{sub 3}{center dot}3H{sub 2}O was investigated as a function of dehydration temperature (100-600C) and dehydration time, using solid-state {sup 23}Na and {sup 27}Al nuclear magnetic resonance with high-speed magic-angle spinning (MAS). {sup 23}Na and {sup 27}Al MAS NMR spectra were recorded at field strengths of 8.4, 11.7, and 14.0 T. The field dependence of the NMR measurements aid in determining the presence of a number of chemically distinct sodium and aluminum sites. The MAS NMR results indicate that both untreated and dehydrated Na{sub 2}O{center dot}Al{sub 2}O{sub 3}3H{sub 2}O contain three chemically distinct sodium sites and one aluminum site. Simulation of the observed {sup 23}Na and {sup 27}Al spectra yields quadrupole coupling constants and asymmetry parameters for each sodium and aluminum site which, when used in combination with isotropic chemical shift measurements, permit various structures to be assigned to the sodium and aluminum sites. Water weight-loss measurements indicate that all structural changes observed in both the {sup 23}Na and {sup 27}Al NMR spectra are related to the progress of dehydration, although not all the water is removed, even after heating at 598C for extended times.