2-DIMENSIONAL TRIPLE-QUANTUM NA-23 MAS NMR-SPECTROSCOPY OF SODIUM-CATIONS IN DEHYDRATED ZEOLITES

Two-dimensional triple-quantum (2D-3Q) Na-23 MAS NMR spectroscopy has been applied for the investigation of sodium cations in dehydrated zeo lites NaY, NaEMT, NaZSM-5 and NaMOR. The experiments have shown that t he new 2D-3Q technique allows the determination of the isotropic chemi cal shifts and quadrupolar couplings of sodium cations with SOQE (seco nd-order quadrupolar effect) parameters of up to ca. 4 MHz. In the pre sent work, SOQE parameters of 1.0-1.2 MHz were found for sodium cation s located at positions SI in the hexagonal prisms of dehydrated zeolit es NaY and NaEMT. The sodium cations located in the 10-ring and 12-rin g channels of dehydrated zeolites NaZSM-5 and NaMOR, respectively, are characterized by a SOQE parameter of 2.0 MHz while a value of 3.1 MHz was determined for sodium cations in the sidepockets of the channels in dehydrated NaMOR. Published by Elsevier Science B.V.