Chemical shift ranges faujasites

B) Various zeolites, namely H-beta, NaA and Faujasite are depicted to scale with the 0.44 nm diameterxenon atoms. Awide range of xenon chemical shifts are observed in these materials. 

Since the initial work of Lippmaa et al. [18], there have been many studies of the Si MAS NMR spectra of low Si/Al ratio zeolites. The general features of these spectra are now well understood, and results from the early studies have been reviewed [1]. In general, the Si MAS NMR spectra of simple zeolites contain a maximum of five reasonably well-resolved peaks, as illustrated in Fig. 5 for the zeolite analcite. It was demonstrated by Lippmaa et al. [18] that these five peaks correspond to the five possible distributions of Si and Al around a silicon nucleus at the center of an Si04 tetrahedron namely, Si[4Al], Si[3Al, lSi], Si[2Al, 2Si], Si[Al, 3Si], and Si[4Si]. In addition, as shown in Fig. 6, the ranges of chemical shift over which the resonances occur are reasonably characteristic of the composition of the first coordination sphere, and the spectra may thus be used to probe the local Si/Al distributions in simple zeolite lattices. A particularly useful feature of these spectra is that the Si/Al ratio of the lattice can be calculated directly. This possibility has been investigated in detail for the previously described zeolite faujasite, which can be obtained by direct synthesis with the same basic structure but over a wide range of compositions (Si/Al = 1 -... 

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