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  • 1
    Electronic Resource
    Electronic Resource
    129Xe-NMR study of coke distribution in dealuminated HY zeolites (1990)
    Springer
    Catalysis letters 5 (1990), S. 143-154 
    Details
    ISSN: 1572-879X
    Keywords: NMR ; xenon ; coke ; zeolite ; extra-framework aluminium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Zeolites coking has been studied by129Xe-NMR technique. The distribution of the coke is heterogeneous on the supercage surface at low cokage level. When coking increases up to 10% the supercages are lined with coke and the residual internal volume consists of narrow channels. Beyond 10% the coke also affects the external surface of the zeolites, with the formation of coke microcavities between the crystallites. This technique has also enabled us to show the role of extra-framework Al in the cracking activity of zeolites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00763946
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  • 2
    Electronic Resource
    Electronic Resource
    Laser-Induced Fluorescence of Base Adsorbed on Surface Sites in Solid Catalysts (2000)
    Springer
    Journal of fluorescence 10 (2000), S. 261-261 
    Details
    ISSN: 1573-4994
    Keywords: Solid catalyst surfaces ; laser-induced luminescence ; acid sites ; quinoline
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The interaction of quinoline with the surface of Nafion-H and Nafion-H (13 wt%)/silica gel composites, silica gel itself, HY zeolite, dealuminated or not, and two types of alumina is studied by laser-induced fluorescence. Strong Brønsted acid sites interact with quinoline to form the quinolinum, that ion being revealed by a band peaking at 390 nm. When Lewis acid sites are present, a complex formed between these sites and quinoline is observed. A dimeric species and the diffusion of the adsorbates on the surface of the Nafion-H polymer are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009449127193
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Analysis of Solid Catalysts Surfaces Using Laser-Induced Luminescence Diagnosis (1997)
    Springer
    Journal of fluorescence 7 (1997), S. 377-380 
    Details
    ISSN: 1573-4994
    Keywords: Solid catalyst surfaces ; laser-induced luminescence ; Y zeolites ; copper ions ; acid sites ; quinoline
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Two applications of laser-induced luminescence spectroscopy for characterizing species at low concentrations in Y zeolites are reported. In reduced copper-exchanged NaY zeolites, time-resolved laser-induced phosphorescence of Cu+ ions allows the determination of the density of different Cu+ sites, while in acidic Y zeolites, adsorption sites of an aromatic base, quinoline, are identified by laser-induced fluorescence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022502731418
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Determination of the quadrupole coupling from featureless line shapes (1994)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 32 (1994), S. 24-28 
    Details
    ISSN: 0749-1581
    Keywords: Solid-state ; 87Rb ; NMR ; Quadrupole frequency ; Featureless lineshapes ; RbCaF3 ; Point defects ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: NMR nutation and quadrupole echo experiments were used to determine the quadrupole frequency (ωQ) of 87Rb (I = 3/2) in a single crystal of RbCaF3. Since RbCaF3 has a cubic unit cell above 195 K, there is no second-order quadrupole shift and the spectrum is rather featureless. By fitting the response of 87Rb, as a function of pulse duration, to the predicted response we were able to determine that the average ωQ/2π = 4.5 kHz in this sample. Discrepancies in the agreement between the theory and the experiment for the echo response were attributed to differential relaxation of the central and satellite transitions.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260320106
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    Paper (German National Licenses)
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