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Combining macroscopic and microscopic diffusion studies in zeolites using NMR techniques |
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| Authors: | Banas Krzysztof Brandani Federico Ruthven Douglas M Stallmach Frank Kärger Jörg |
| Institution: | 1. Fakultät für Physik und Geowissenschaften, Universität Leipzig, D-04103 Linnestrasse 5, Germany;2. Department of Chemical Engineering, University of Maine, Orono, Maine 04469-5737;1. Biogen Idec Corporation, Bioprocess Development, 14 Cambridge Center, MA 02142, USA;2. Swedish Orphan Biovitrum, Purification Process Development, SE-112 76 Stockholm, Sweden;1. Department of CSE, VITAM, Berhampur-761008, Odisha, INDIA;2. Department of CS, Government College, Koraput-764021, Odisha, INDIA;3. Sysnet Global Tech Pvt. Ltd., Sambalpur-768002, Odisha, INDIA;1. Department of Chemical Engineering, University of California Davis, Davis, CA 95616, United States;2. Department of Materials Science and Engineering, University of California Davis, Davis, CA 95616, United States;3. Lawrence Livermore National Laboratory, Livermore, CA, United States;1. Center for Materials Science and Nanotechnology (SMN), Department of Chemistry, University of Oslo, P.O. Box 1033, Blindern, N-0315 Oslo, Norway;2. Haldor Topsøe A/S, Haldor Topsøes Allé 1, 2800 Kgs. Lyngby, Denmark;3. Department of Chemistry, NIS and INSTM Reference Centre, University of Turin, Via G. Quarello 15, I-10135 and Via P. Giuria 7, I-10125 Turin, Italy |
| Abstract: | In this study the zero length column (ZLC) technique is extended to the case where the decay of the adsorbed phase concentration is observed directly by nuclear magnetic resonance (NMR). An adsorption-desorption apparatus compatible with a 400-MHz NMR spectrometer was developed. It operates with nitrogen or helium as the inert purge gas. The column of the adsorbent material is placed in the sensitive region of the superconducting magnet and the rf coil of the NMR spectrometer. The time scales of the adsorption and desorption processes depend on concentration, temperature and crystal shape and are found to be in the range of 1-10 min. From the desorption branch, the non-equilibrium ZLC-NMR measurements yield intracrystalline diffusion coefficients in the range of 10(-13) to 10(-11) m2/s for different alkanes in silicalite-1. These values are always found to be smaller than the values measured by pulsed field gradient NMR under equilibrium condition indicating that there must be additional transport resistance at the external surface of these silicalite-1 zeolite crystals. |
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