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  • 1
    Electronic Resource
    Electronic Resource
    The structure and the dynamics of the ordered solid phase of CBr4, a rigid molecule model (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 1948-1954 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Various known parameters of the atom–atom potential for the bromine atoms interaction have been used to model the experimental structure and the cohesive energy of the ordered phase II of CBr4. The set of parameters corresponding to krypton has turned out to give the best agreement with the experimental observations. The frequencies of the lattice vibrations at the zone center and the elastic constants have then been calculated and shown to be in a good quantitative agreement with the existing experimental data. The validity of the rigid molecule approach has been briefly discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459072
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  • 2
    Electronic Resource
    Electronic Resource
    Electron microscopic characterization of Cr/silica catalyst for ethylene polymerization (1992)
    Springer
    Catalysis letters 15 (1992), S. 145-153 
    Details
    ISSN: 1572-879X
    Keywords: SEM characterization ; TEM characterization ; Cr/silica catalyst ; ethylene polymerization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Ethylene polymerization was carried out over both porous and non-porous 5 wt% Cr/silica catalysts in a slurry reactor. The polymerization was stopped at selected times to obtain samples for SEM and TEM characterization. Despite the different physical characteristics of the two silica-supported catalysts and their different behavior in the early stages of reaction, high resolution SEM micrographs (taken after runs of longer duration) revealed similar, fibrous and very porous polymer layers on both. This accessibility of the ethylene enables transport of monomer to the active sites at the very high reaction rates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00770907
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Identification of Cr oxidation state active in ethylene polymerization on Cr/SiO2 at room temperature (1992)
    Springer
    Catalysis letters 13 (1992), S. 331-339 
    Details
    ISSN: 1572-879X
    Keywords: Ethylene polymerization ; silica-supported chromium catalyst ; IR ; CO adsorption ; oxidation states of active Cr sites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract High temperature treatment under vacuum or in a pure N2 atmosphere can be used instead of a reduction step to activate Cr/SiO2 catalysts used for ethylene polymerization. After this procedure, the Cr species active over a range of temperature has been identified as Cr(III) using CO adsorption (IR triplet bands at 2228, 2214, and 2202 cm−1) and an ethylene polymerization activation energy of 12.1 kcal/mol. The Cr(III) species has also been shown to be present after activation using CO reduction, the more commonly used procedure. Cr(II) sites are always present when activation involves reduction with CO and become increasingly active as the temperature rises above room temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00765035
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    Paper (German National Licenses)
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