MULTINUCLEAR MAS NMR SPECTROSCOPIC STUDY OF THE ZEOLITE, MCM-22

The sodium form of the novel silica-rich zeolite MCM-22 of moderate Si/Al ratio (44) has been synthesized hydrothermally and studied by multinuclear (H-1, Al-27 and Si-29) magic-angle spinning (MAS) NMR spectroscopy. Al-27 spectra indicate that, in the as-synthesized (CN) and calcined materials, all the aluminium atoms are in the tetrahedral framework positions. The silicon resonance at delta = -105.1 in the calcined material is found to correspond to Q(4)(1Al) and tetrahedral-sites (T-sites), T-2 + T-6[Q(4)(0Al)] of the orthorhombic structure. Silanol, Q(4)(1Al) and crystallographically non-equivalent Q(4)(0Al) lattice sites are identified and information has been gathered on the interaction between the template protons and the lattice T-sites through H-1-Si-29 cross-polarization dynamics experiments. Our results also indicate that in the as-synthesized material, the Si-29 resonances at delta = -104.3 and -120.9 correspond to distant T-sites that are located away from the template molecules in the zeolite pores.