Journal of physical chemistry vol:97 issue:19 pages:5132-5135
In the Si-29 MAS NMR spectra of Na-exchanged FAU/EMT zeolite intergrowths, 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 resonance 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 method is applicable to EMT/FAU samples containing Si(4Al) environments and is illustrated for ZSM-2 and ZSM-3.