title: The influence of adsorbed molecules on Na-sites in NaY zeolite investigated by triple-quantum 23Na MAS NMR spectroscopy.
abstract: The effect of hydration and benzene adsorption on 23Na resonance and the quadrupolar interaction in NaY zeolites is studied by triple-quantum MAS 23Na NMR spectroscopy. In the case of a C6D6/NaY system, the results show that with an increase in benzene loading, there is an up-field trend in isotropic chemical shift (delta CS) and a decreasing second order quadrupolar effect (chi s) for the site II sodium ions. It was found that adsorbed benzene molecules have a slight effect on the environment of sodium ions on site I. All the sodium sites in NaY are influenced upon hydration. The up-field shift of the sodium delta CS reflects the effect of coordination of oxygen atoms on sodium cations due to hydration. The magnitude of chi s for hydrated sodium sites increases and then falls off with water loading. The increase in chi s is due to the initial hydration among SI-, SI'- and SII-sodium ions, while the decrease is the result of approaching the final stage of saturated hydration.
authors.affiliation: Department of Chemistry, National Taiwan University, Taipei.
authors.forename: K N
authors.initials: KN
authors.lastname: Hu
authors.forename: L P
authors.initials: LP
authors.lastname: Hwang
mesh_terms: D000327:Adsorption; D001554:Benzene / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008958:Models, Molecular; D011789:Quantum Theory; D012964:Sodium / Q000737:chemistry*; D012975:Sodium Isotopes; D014867:Water / Q000737:chemistry; D015019:Yttrium / Q000737:chemistry*; D017641:Zeolites / Q000737:chemistry*
chemical_list: D012975:Sodium Isotopes; D014867:Water; D017641:Zeolites; D015019:Yttrium; D012964:Sodium; D001554:Benzene