ADSORPTION AND XE-129 NMR OF XENON IN SILVER-EXCHANGED Y-ZEOLITES - APPLICATION TO THE LOCATION OF SILVER CATIONS

The adsorption isotherms and Xe-129 n.m.r. chemical shifts of xenon in silver-exchanged yAgNaY zeolites (y from 5 to 100%) after high-temperature (400-degrees-C) dehydration as well as subsequent oxidation were measured at 26-degrees-C. A three-site sorption model taking into account adsorbate-adsorbate interaction was developed that reproduces simultaneously the adsorption isotherms and the chemical shift vs. concentration curves up to xenon loadings of about 6 atoms/supercage. The upfield displacements of the chemical shifts in the silver-exchanged zeolites with respect to NaY are attributed to the interaction of xenon with a small portion of the supercage silver cations, probably those unlocalized or residing on crystallographic SIII sites.