Details
| Original language | English |
|---|---|
| Pages (from-to) | 98-103 |
| Number of pages | 6 |
| Journal | Microporous and Mesoporous Materials |
| Volume | 120 |
| Issue number | 1-2 |
| Early online date | 3 Jul 2008 |
| Publication status | Published - 1 Apr 2009 |
Abstract
The pulsed field gradient (PFG) NMR technique has been applied for studying molecular diffusion of a series of aromatics in zeolite NaX. For a loading of one molecule per supercage and a measuring temperature of 105 °C, the diffusivities of benzene and the diisopropylbenzene isomers are found to differ by one order of magnitude. Complementary measurements with zeolite specimens of different origin and comparison with literature data illustrate the scattering in the diffusivity data which may result from measurements with different measuring techniques and/or different zeolite material. Benzene is identified as a reliable probe molecule for comparison of the diffusion properties of different zeolite specimens. In this way, after more than 20 years, the diffusivity data in identical specimens could be reproduced and thus be confirmed to exceed the diffusivity in a specimen of apparently identical type, but of different origin, by a factor of about two, indicating the existence of additional intracrystalline resistances. Simultaneously with examples demonstrating the self-consistency of the attained data, a critical assessment of the limitations and possible pitfalls of the application of PFG NMR to diffusion measurements in zeolites are presented.
Keywords
- Aromatics, Benzene, Pulsed field gradient NMR, Self-diffusion, Zeolite NaX
ASJC Scopus subject areas
- Chemistry(all)
- Materials Science(all)
- Physics and Astronomy(all)
- Condensed Matter Physics
- Engineering(all)
- Mechanics of Materials
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In: Microporous and Mesoporous Materials, Vol. 120, No. 1-2, 01.04.2009, p. 98-103.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Diffusion of aromatic guest molecules in zeolite NaX studied by pulsed field gradient NMR
AU - Ulrich, Konstantin
AU - Freude, Dieter
AU - Galvosas, Petrik
AU - Krause, Cordula
AU - Kärger, Jörg
AU - Caro, Jürgen
AU - Poladli, Polad
AU - Papp, Helmut
PY - 2009/4/1
Y1 - 2009/4/1
N2 - The pulsed field gradient (PFG) NMR technique has been applied for studying molecular diffusion of a series of aromatics in zeolite NaX. For a loading of one molecule per supercage and a measuring temperature of 105 °C, the diffusivities of benzene and the diisopropylbenzene isomers are found to differ by one order of magnitude. Complementary measurements with zeolite specimens of different origin and comparison with literature data illustrate the scattering in the diffusivity data which may result from measurements with different measuring techniques and/or different zeolite material. Benzene is identified as a reliable probe molecule for comparison of the diffusion properties of different zeolite specimens. In this way, after more than 20 years, the diffusivity data in identical specimens could be reproduced and thus be confirmed to exceed the diffusivity in a specimen of apparently identical type, but of different origin, by a factor of about two, indicating the existence of additional intracrystalline resistances. Simultaneously with examples demonstrating the self-consistency of the attained data, a critical assessment of the limitations and possible pitfalls of the application of PFG NMR to diffusion measurements in zeolites are presented.
AB - The pulsed field gradient (PFG) NMR technique has been applied for studying molecular diffusion of a series of aromatics in zeolite NaX. For a loading of one molecule per supercage and a measuring temperature of 105 °C, the diffusivities of benzene and the diisopropylbenzene isomers are found to differ by one order of magnitude. Complementary measurements with zeolite specimens of different origin and comparison with literature data illustrate the scattering in the diffusivity data which may result from measurements with different measuring techniques and/or different zeolite material. Benzene is identified as a reliable probe molecule for comparison of the diffusion properties of different zeolite specimens. In this way, after more than 20 years, the diffusivity data in identical specimens could be reproduced and thus be confirmed to exceed the diffusivity in a specimen of apparently identical type, but of different origin, by a factor of about two, indicating the existence of additional intracrystalline resistances. Simultaneously with examples demonstrating the self-consistency of the attained data, a critical assessment of the limitations and possible pitfalls of the application of PFG NMR to diffusion measurements in zeolites are presented.
KW - Aromatics
KW - Benzene
KW - Pulsed field gradient NMR
KW - Self-diffusion
KW - Zeolite NaX
UR - http://www.scopus.com/inward/record.url?scp=60649087130&partnerID=8YFLogxK
U2 - 10.1016/j.micromeso.2008.06.031
DO - 10.1016/j.micromeso.2008.06.031
M3 - Article
AN - SCOPUS:60649087130
VL - 120
SP - 98
EP - 103
JO - Microporous and Mesoporous Materials
JF - Microporous and Mesoporous Materials
SN - 1387-1811
IS - 1-2
ER -