The unique catalytic and adsorbent properties, crystal structures, ion-exchange and other characteristics of zeolites have been extensively investigated in recent years. The high-resolution solid-state
29Si-and
27Al-nuclear magnetic resonance (NMR) with magic angle spinning (MAS) have proved to be an useful tool for the chemical structural characterization of zeolites.
The article reviews how high-resolution solid-state NMR with MAS reveals unique insights into zeolite structures from recent literatures. Since five distinct Si-Al configurations, Si (OAl)
n (OSi)
4-n (n=0-4), in zeolitic frameworks can be identified by
29Si-MAS NMR, several interesting problems have been enthusiastically discussed on
29Si-NMR analysis. In the present paper, the following topics are introduced and discussed:(1) Assignments of
29Si-chemical shifts and Si-Al configurations for aluminosilicates.(2) Discussion of Loewenstein's rule, the presence of Al-O-Al ordering, in the zeolite A.(3) Characteristic changes of Si/Al ratio in faujasites (zeolites X and Y) and mordenite studied by
29Si-NMR spectra.(4)
29Si-NMR spectral studies on the framework structures of pentasil zeolites such as ZSM-5, ZSM-11 and silicalite.(5) Stuidies of Ga
3+ substitution for Al
3+ in the zeolitic frameworks of faujasites studied by
29Si-NMR spectra.(6) Other
29Si-NMR spectral studies on zeolitic framework. On the other hand,
27Al-NMR has been used to estimate the compositions on tetrahedrally and octahedrally coordinated aluminum states. For instance, the dealumination mechanisms have been investigated by the
27Al-NMR spectral behaviors.
Furthermore the application of high-resolution solid-state
13C-NMR to the characteristic changes of organic compounds, in the zeolitic frameworks has been discussed.
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