MCM-22 is a new molecular sieve which is expected to be widely used in chemical industry. In this paper we study the ²⁷Al species of different acid sites in the MCM-22. ²⁷Al spectra of samples rehydrated in differently extent have been acquired. It is difficult to get high resolution ²⁷Al spectrum of the dehydration powder sample directly because of the existence of strong quadrupole interaction which comes from asymmetric local chemical environment. In order to overcome the strong quadrupole interaction of ²⁷Al, the double resonance NMR method ¹H/²⁷Al TRAPDOR is used in this study. Quadrupole coupling constants (QCC) for aluminum species are abtained. By calculation of the second order quandrupole line width of these aluminum species , it can be concluded that 4-, 3-coordinate framework aluminum and extra-framework alumium are all the source of the “NMR invisible aluminum”.

MCM-22, TRAPDOR, Acid sites, Quadrupole coupling con