DISTRIBUTION OF TETRAHEDRAL ALUMINUM SITES IN ZSM-5 TYPE ZEOLITES - AN AL-27 (MULTIQUANTUM) MAGIC-ANGLE-SPINNING NMR-STUDY

Up to now the distribution of Al atoms in the zeolite lattice could be monitored mainly by Si-29 MAS NMR. The data about the nonequivalent a luminium T sites, present in the Al-27 MAS NMR spectra, was obscured b y second-order effects of quadrupolar interaction. By applying the fiv e-quantum Al-27 MQMAS NMR method to ZSM-5 type zeolites, we were able to distinguish at least two nonequivalent aluminium T sites in the H-Z SM-5 and establish the relation between Al-27, Si-29, and H-1 NMR data . Comparison with Si-29 MAS NMR spectra gives information about the di stribution and siting of aluminium in the zeolite framework.