Journal of Physical Chemistry, Vol.98, No.28, 7056-7062, 1994
New Assignment of the Signals in Na-23 Dor NMR to Sodium Sites in Dehydrated NaY Zeolite
A new assignment of the signals in the Na-23 DOR NMR spectra to the different sodium sites in dehydrated NaY zeolite is presented. Na-23 DOR and MAS NMR measurements of dehydrated NaY, Ca2+-exchanged NaY samples, and NaY samples in which Mo(CO)6 is adsorbed are used for this purpose. Four distinct signals in the Na-23 DOR NMR spectra of dehydrated NaY are found : the first signal with an isotropic chemical shift of -6 ppm and a quadrupolar coupling constant of 0.4 MHz is assigned to the Na+ cations at site I. The second signal, with an isotropic chemical shift of -12 ppm and a quadrupolar coupling constant of 2.3 MHz, is assigned to the Na+ cations at sites I’/II’. The third and the fourth signals, with isotropic chemical shifts of -4 and 5 ppm and quadrupolar coupling constants of 4.2 and 4.7 MHz, respectively, are assigned to the Na+ cations at sites II and III.
Keywords:DOUBLE-ROTATION NMR;FAR-INFRARED SPECTROSCOPY;Y-ZEOLITES;NUTATION NMR;MAS NMR;ADSORPTION;IONS