Beckert, Steffen

Freude, Dieter

Haase, Jürgen

Kärger, Jörg

Stallmach, Frank

English

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The Open-Access Journal for the Basic Principles of Diffusion Theory, Experiment and ApplicationIon and water mobility in hydrated Li-LSX zeolite studied by 1H, 6Li and7Li NMR spectroscopy and diffusometryDieter Freude∗, Steffen Beckert, Frank Stallmach, Jörg Kärger, Jürgen HaaseUniversität Leipzig, Institut für Experimentelle Physik, Leipzig, Germany∗freude@uni-leipzig.deCrystallites of zeolite LSX with a diameter of about 10 µm are shown to allow the simultaneous inves-tigation of intracrystalline mass transfer phenomena of water molecules and lithium ions in hydratedzeolite Li-LSX by NMR diffusometry. By MAS NMR spectroscopy with the 1H and 6Li nuclei, thewater molecules and lithium ions are found to yield two signals, a major and a minor one, which maybe attributed to locations in the sodalite cages and the supercages, respectively. By 1H and 6Li exchangespectroscopy the mean residence times in the sodalite cages at 373 K are found to be about 150 ms forthe water molecules and about 40 ms for the lithium cations [1].As to our knowledge, PFG NMR measurements of cation diffusion in zeolites have never been per-formed. Whilst, under the given experimental conditions, the water diffusivity at 373 K could be deter-mined to be of the order of 2.5 × 10−10 m2s−1 or even larger, the diffusivity of the lithium ions in thesame sample and at the same temperature was found to be (2.0 ± 0.8) × 10−11 m2s−1. This yields to aHaven factor of about 10 for the ion conductivity in the zeolite Li-LSX.The new options provided by the high-intensity device for PFG NMR diffusion measurement appliedin this study for the measurement of the intracrystalline diffusion of both the cations and the guestmolecules in zeolite Li-LSX, in purposeful combination with the information accessible by PFG MASNMR and two-dimensional MAS NMR spectroscopy, have all potentials for opening new routes fora deeper understanding of the dynamic processes in host-guest systems under the involvement of ex-changeable cations.Figure 1: Water and ion diffusion in the package of zeolite crystallites.References[1] D. Freude, S. Beckert, F. Stallmach, R. Kurzhals, D. Täschner, H. Toufar, J. Kärger, J. Haase: Ionand water mobility in hydrated Li-LSX zeolite studied by 1H, 6Li and 7Li NMR spectroscopy anddiffusometry. Microporous Mesoporous Materials 172, 174–181 (2013)

Ion and water mobility in hydrated Li-LSX zeolite studied by 1 H, 6 Li and 7 Li NMR spectroscopy and diffusometry

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Ion and water mobility in hydrated Li-LSX zeolite studied by 1 H, 6 Li and 7 Li NMR spectroscopy and diffusometry

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