Characterization of Metakaolinite with Multiple Quantum MAS NMR

Metakaolinite produced by thermal transformation from kaolinite was studied by 27Al multiple quantum magic angel spinning (MQMAS) NMR technique in addition to 1-dimensional 27Al and 29Si MAS NMR. Our results confirm that 4-, 5-, 6- coordinated aluminum sites co-exit with some distribution of isotropic chemical shifts. This is consistent with amorphous character of metakaolinite observed with X-ray diffraction. In addition, characterization with MQMAS is briefly discussed in comparison with other NMR techniques to identify different aluminum sites especially when peaks are severely overlapped in 1-dimensional 27Al MAS NMR spectra.