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  • 2000-2004  (2)
  • 1995-1999  (2)
  • 1980-1984
  • 1965-1969
  • cloud point  (2)
  • oxidative dehydrogenation  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Promoting effect of carbon dioxide on the dehydrogenation and aromatization of ethane over gallium‐loaded catalysts (2000)
    Springer
    Catalysis letters 64 (2000), S. 215-221 
    Details
    ISSN: 1572-879X
    Keywords: gallium oxide ; titanium oxide ; carbon dioxide ; oxidative dehydrogenation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Ga2O3 and Ga2O3/TiO2 catalysts were found to be effective agents for the dehydrogenation of ethane to ethene in the presence of carbon dioxide at 650 °C. The activity of the Ga2O3 and Ga2O3/TiO2 catalysts in the presence of CO2 was 2–4 times higher than that without CO2. Ethene yields reached ca. 20–25% and selectivity was ca. 70–90% at 650°C in the 17% ethane and 83% CO2 feed at an SV of 9,000 ml/(g‐cat h). The presence of CO2 markedly promoted dehydrogenation of ethane over Ga2O3 and Ga2O3/TiO2 catalysts. Furthermore, the promoting effect of CO2 on the aromatization of ethane and ethene over a Ga2O3+H/ZSM‐5 catalyst was also observed above 650 °C. Aromatics yields were higher than those without CO2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019047306179
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Dehydrogenation of isopropylbenzene with vanadium-oxide-loaded activated carbon catalyst in the presence of carbon dioxide (2000)
    Springer
    Catalysis letters 69 (2000), S. 59-64 
    Details
    ISSN: 1572-879X
    Keywords: dehydrogenation ; oxidative dehydrogenation ; cumene ; α-methylstyrene ; vanadium oxide ; activated carbon ; temperature-programmed reduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Dehydrogenation of isopropylbenzene to α-methylstyrene was carried out using various supported metal oxide catalysts in the presence of carbon dioxide. An activated carbon-supported vanadium oxide catalyst afforded a high activity in carbon dioxide atmosphere: the α-methylstyrene yield in carbon dioxide atmosphere was two times greater than that in an argon atmosphere at 723 K. In order to investigate the role of carbon dioxide in this reaction, we carried out temperature-programmed reduction (TPR) studies using both fresh and used catalysts. The TPR profiles clearly indicate that carbon dioxide could keep the surface of vanadium oxide at a high oxidation state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019084915149
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Physical Stability of Ethyl Diatrizoate Nanocrystalline Suspension in Steam Sterilization (1999)
    Springer
    Pharmaceutical research 16 (1999), S. 569-574 
    Details
    ISSN: 1573-904X
    Keywords: nanocrystals ; submicron crystals ; suspensions ; steam sterilization ; physical stability ; surfactants ; cloud point ; ethyl diatrizoate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To study the effects of formulation variables on the physical stability of a submicron crystal (nanocrystal) suspension under steam sterilization conditions. Methods. Suspensions of ethyl diatrizoate nanocrystals were prepared by wet milling in the presence of the surfactant poloxamine 908. Particle size distribution and zeta potential were measured by photon correlation spectroscopy. Results. On heating, the mean particle size of the nanocrystal suspension remained essentially unchanged up to 110°C, the cloud point of the stabilizing surfactant, but increased significantly above that temperature. The increase in particle size was a result of particle aggregation rather than crystal growth. Adding a cloud point booster to the suspension significantly minimized the particle aggregation at high temperatures. The purity of poloxamine 908 and the tonicity agent and buffer salt used also affected the heat stability of the suspension, the latter agents apparently through altering the surfactant cloud point. Conclusions. The aggregation of the ethyl diatrizoate nanocrystalline suspension under steam sterilization conditions was a result of phase separation of the stabilizing surfactant at its cloud point. When formulated with a cloud point booster to prevent the phase-separation, the suspension maintained its physical stability under steam sterilization without any significant change in particle size distribution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018883431970
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Cloud Point of Nonionic Surfactants: Modulation with Pharmaceutical Excipients (1999)
    Springer
    Pharmaceutical research 16 (1999), S. 562-568 
    Details
    ISSN: 1573-904X
    Keywords: nonionic surfactants ; cloud point ; cloud point boosters ; poloxamers ; poloxamines ; liquid formulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To determine the cloud point of a variety of nonionic surfactants and to search for means to raise the surfactant cloud point in liquid formulations. Methods. Cloud points of nonionic surfactants were determined visually in a water bath. Organic compounds, many of which have been used as pharmaceutical excipients, were tested initially for effect on the cloud point of poloxamine 908. Four effective cloud point boosters (CPBs) from different structural classes were further tested on additional surfactants. Results. A number of compounds can raise the cloud point of nonionic surfactants. These cloud point boosters are classified into two categories: nonionic and ionic. The nonionic CPBs include poly(ethylene glycols), propylene glycol, methanol, ethanol, isopropanol, and 2-hydroxypropyl-β-cyclodextrin. They are effective at molar concentrations. The ionic CPBs include anionic and cationic surfactants, charged phospholipids, long chain fatty acids, and bile salts. They are effective at millimolar concentrations. Conclusions. The cloud point of nonionic surfactants used in liquid formulations can be modulated through the proper choice of excipient.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018831415131
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    Paper (German National Licenses)
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