Comparison of the dynamics of n-hexane in ZSM-5 and 5A zeolite structures
Boreskov Institute of Catalysis, Siberian Branch of the Russian Academy of Sciences, Prospekt Akademika Lavrentieva 5, 630090, Novosibirsk, Russia
2 Institut de Recherches sur la Catalyse, CNRS, 2 av. Albert Einstein, 69626, Villeurbanne, France
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The translational and rotational dynamics of n-hexane adsorbed in ZSM-5 and 5A zeolites has been studied by neutron scattering and deuterium solid-state NMR, at various temperatures. The dynamics of n-hexane is quite different in the two zeolites. In the ZSM-5 structure, the molecule sits in channel segments, the energy barrier between adjacent adsorption sites is small and fast anisotropic motions are observed. In the 5A zeolite, the molecule is adsorbed in -cages; the barrier between adjacent cages is larger so that the molecule spends a longer time exploring the volume of an -cage, leading to a more isotropic motion. The diffusion coefficient of the molecule is reduced by more than 4 orders of magnitude in 5A zeolite compared with ZSM-5.
© EDP Sciences, Società Italiana di Fisica, and Springer-Verlag, 2003