NMR Study of Local and Long Range Dynamics of Adsorbed Water in Zeolite NaY(Br)

Abstract

AbstractThe dynamics of partially deuterated water in zeolite NaY(Br) are investigated by a combination of several NMR methods for two different loadings, 4 water molecules and 18 water molecules per supercage. Information on local dynamics is obtained by1H and2H NMR spin-lattice relaxation,2H NMR solid-echo spectra and2H NMR stimulated echo decay curves. The water long range diffusion has been studied by1H NMR static field gradient experiments. The most important findings are as follows: The mechanism of water dynamics depends strongly on the degree of loading. This is clearly reflected in both, local and long range motion. The intermediate2H NMR spectra might be explained referring to a model proposed by O'Hare et al.: It is based on two different populations of water molecules performing tetrahedral jumps respectively C2-flips of their OH bonds. Alternative models for the local water dynamics, distorted tetrahedral jumps and a distribution of correlation times, are also discussed.