XE-129 NMR CHEMICAL-SHIFTS AND LINEWIDTHS OF XENON IN ZEOLITES ZNY .1. THE EFFECT OF THE PREPARATION TECHNIQUE ON THE DISTRIBUTION OF THE ZINC CATIONS

Zinc-containing zeolites of type Y have been prepared from NaY via ion exchange with zinc salt solutions, from NH4Y via the solid-state ion exchange with zinc chloride, and from HY by reaction with zinc vapour. Xenon and carbon monoxide adsorption as well as Xe-129 NMR techniques were used to analyse these samples with respect to the zinc cation co ncentration and distribution among the supercage sites. In addition, a n inhomogeneous distribution of the supercage zinc cations among the z eolite crystallites was deduced from the pressure dependence of the wi dths of the Xe-129 NMR resonance lines. The zeolites prepared via the solid-state exchange and vapour reaction techniques exhibit more homog eneous cation distributions than the zeolites exchanged conventionally .