PHASE DISCRIMINATION WITH SI-29 MAS NMR IN EMT FAU ZEOLITE INTERGROWTHS

In the Si-29 MAS NMR spectra of Na-exchanged FAU/EMT zeolite intergrow ths, the signals from the FAU and EMT phases coincide. However, after Li ion exchange of such zeolites, an upfield shift of the FAU signals by 2-3 ppm occurs and, consequently, partial resolution of the resonan ce signals is possible. Thus the combination of Si-29 MAS NMR spectra of the Na- and Li-exchanged forms of an EMT/FAU zeolite allows one to determine the Si,Al distribution in the FAU and EMT phases separately as well as the relative amounts of each phase in the sample. The metho d is applicable to EMT/FAU samples containing Si(4Al) environments and is illustrated for ZSM-2 and ZSM-3.