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The prominent band in the Raman spectra of a zeolitic framework in the 300-600-cm-~ region is found to be sensitive to the ring structures present in the framework. In the case of zeolites with even-membered rings such as 4,6,8,10, and 12 rings, the band is around 500 cm-l. The presence of five-membered rings leads to a lowering of this frequency to 390-450 cm-I. For the ferrierite family of zeolites with 5-, 6-, 8-, and IO-membered rings, this band is at 430 cm-I. The absence of eight-membered rings in this set increases the frequency to 450 cm-I, as in ZSM-23 and NU-10. The presence of 4-, 5-, 6-, 8-, IO-, or 12-membered rings, as in ZSM-5, mordenite, and ZSM-48 leads to bands at 390 and 460 an-'. This empirical correlation could be of considerable value in determining zeolitic framework structure.

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