SODIUM-CATION LOCATIONS IN ZEOLITE-OMEGA STUDIED BY NA-23 VASS NMR

Overlapping Na-23 NMR signals of zeolite Na-omega are observed by a 2D MAS quadrupolar nutation NMR spectrum and VASS NMR spectra. The low-field Lorentzian shape component centered at -3 ppm is assigned to the signal of mobile Na+ cations located in twelve-membered ring channels. The high-field component, varying considerably with the spinning angles of VASS NMR spectra, is assigned to the signal of less mobile Na+ cations located in gmelinite cages. The partition between two categories of Na+ cations is determined by the simulation of VASS NMR spectra with the theoretical consideration extended to more general case that both the quadrupolar and chemical shift anisotropic interactions coexist.Chemistry, PhysicalPhysics, Atomic, Molecular & ChemicalSCI(E)5ARTICLE1-382-8723