129Xe NMR chemical shifts and linewidths of xenon in zeolites ZnY. Part 1.—The effect of the preparation technique on the distribution of the zinc cations

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Abstract
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 129Xe NMR techniques were used to analyse these samples with respect to the zinc cation concentration and distribution among the supercage sites. In addition, an inhomogeneous distribution of the supercage zinc cations among the zeolite crystallites was deduced from the pressure dependence of the widths of the 129Xe NMR resonance lines. The zeolites prepared via the solid-state exchange and vapour reaction techniques exhibit more homogeneous cation distributions than the zeolites exchanged conventionally.