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  • Artikel: DFG Deutsche Nationallizenzen  (2)
  • acidic properties  (1)
  • silica  (1)
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  • Artikel: DFG Deutsche Nationallizenzen  (2)
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  • 1
    Digitale Medien
    Digitale Medien
    Synthesis and characterization of niobia-containing aerogels (1992)
    Springer
    Catalysis letters 12 (1992), S. 231-237 
    Details
    ISSN: 1572-879X
    Schlagwort(e): Aerogels ; niobia ; silica ; acidic oxides
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Niobium ethoxide was used as a precursor either by itself to impregnate a silica aerogel or in conjunction with tetraethyl orthosilicate to produce a mixed oxide aerogel. In contrast with bulk niobia, niobia in these samples did not crystallize into the high-temperature form even after calcination at 1273 K. Niobia-silica interactions, which apparently stabilized niobia from crystallization, also introduced acidity as shown by n-butylamine titration and infrared study of pyridine adsorption. Furthermore, niobia on silica was found to have stronger Brönsted acid sites than niobia in silica, in agreement with previous observations on samples prepared with more conventional methods. All these samples were also active in the isomerization of 1-butene.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00767205
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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    Artikel (Nationallizenzen)
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  • 2
    Digitale Medien
    Digitale Medien
    Characterization and selective poisoning of acid sites on sulfated zirconia (1995)
    Springer
    Catalysis letters 32 (1995), S. 241-251 
    Details
    ISSN: 1572-879X
    Schlagwort(e): infrared spectroscopy ; microcalorimetric measurements ; ammonia adsorption ; acidic properties ; sulfated zirconia catalysts
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Microcalorimetric measurements and infrared spectroscopy of ammonia adsorption were used to characterize the acidic properties of sulfated zirconia catalysts. Reaction kinetic measurements forn-butane isomerization were conducted over catalysts that were selectively poisoned with controlled amounts of ammonia. Initial heats of ammonia adsorption on the strong acid sites of sulfated zirconia were 150–165 kJ/mol, and these sites contain Brønsted acid and possibly Lewis acid centers. Sulfated zirconia samples that show high activity for the isomerization ofn-butane possess Bransted acid sites of intermediate strength, with differential heats of ammonia adsorption between 125 and 140 kJ/mol. The results of selective poisoning of sulfated zirconia with ammonia confirm that Bransted acid sites of intermediate strength are active forn-butane isomerization at 423 K while not discounting a possible role of the stronger acid sites.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00813218
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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    Artikel (Nationallizenzen)
    Volltext
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