MULTINUCLEAR SOLID-STATE NMR INVESTIGATION OF ZEOLITE MCM-22

In this paper, the results of the first high-field (B-0 = 17.6 T) Al-2 7 MAS n.m.r. measurement on zeolite MCM-22 are reported. The Si-29 and Al-27 MAS n.m.r, spectra of as-synthesized and dealuminated zeolite M CM-22 were interpreted by signals of framework silicon and aluminum at oms located on at least five crystallographically nonequivalent T site s. After ammonium exchange and calcination of zeolite MCM-22, acidic b ridging OH groups identified by a H-1 MAS n.m.r. signal at 4.2 ppm are formed. Using Si-29 CP/MAS n.m.r, spectroscopy these bridging OH grou ps were attributed to hydroxyl protons bonded via oxygen bridges to Si (1 Al) atoms located on all the at least five crystallographically non equivalent T sites.