Intracrystalline Transport Resistances in Nanoporous Zeolite X |
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Authors: | Armin Feldhoff Dr Jürgen Caro Prof Hervé Jobic Dr Jacques Ollivier Dr Cordula B Krause Petrik Galvosas Dr Jörg Kärger Prof |
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Institution: | 1. Institute of Physical Chemistry and Electrochemistry, Leibniz Universit?t Hannover, Callinstra?e 3‐3 A, 30167 Hannover (Germany), Fax: (+49) 511‐762‐19121;2. Institut de Recherches sur la Catalyse et l'Environnement de LYON, CNRS, Université de Lyon, 2 avenue Albert Einstein, 69626 Villeurbanne (France);3. Institut Laue‐Langevin, BP 156, 38042 Grenoble (France);4. Universit?t Leipzig, Fakult?t für Physik und Geowissenschaften, Linnéstra?e 5, 04103 Leipzig (Germany);5. Current address: School of Chemical and Physical Sciences, Victoria University of Wellington, P.O. Box 600, Wellington 6140 (New Zealand) |
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Abstract: | By applying pulsed‐field gradient nuclear magnetic resonance (PFG NMR) in comparison to quasi‐elastic neutron scattering (QENS), we sense by measurement of the diffusion of n‐octane on different length scales, transport resistances in faujasite type X (which is isostructural with type Y and differs by the lower Si/Al ratio only) with mutual distances of less than 300 nm. Direct observation of the real structure of zeolite X by transmission electron microscopy identifies them as stacking faults of mirror‐twin type on (111)‐type planes of the cubic framework. Thus, direct experimental proof is given that, in general, nanoporous host systems such as zeolite crystals cannot be considered as a mere arrangement of cavities. It is rather the presence of structural defects that dominates their properties as soon as transport phenomena with practical relevance, including chemical conversion by heterogeneous catalysis and chemical separation by molecular sieving and selective adsorption, become relevant. |
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Keywords: | diffusion electron microscopy neutron scattering NMR spectrocopy zeolites |
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