Distribution of Tetrahedral Aluminium Sites in ZSM-5 Type Zeolites:  An 27Al (Multiquantum) Magic Angle Spinning NMR Study

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