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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 7 (1996), S. 79-83 
    ISSN: 1042-7147
    Keywords: hydrogenation ; m-xylene ; polysilazane ; stereochemistry ; platinum complex ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A new kind of inorganic polymer, silica-supported polysilazane (Si-N), and its platinum complex (Si-N-Pt) were prepared and characterized by X-ray photoelectron spectroscopy. It was found that Si-N-Pt can catalyze hydrogenation of m-xylene under mild conditions (30-50°C, 1 atm). The products of the reaction were cis- and trans-1,3-dimethylcyclohexane. The formation of trans-1,3-dimethylcyclohexane may be adequately explained according to the “roll-over” model. The stereoselectivity was influenced by temperature and catalyst concentration, the proportion of the cis isomer decreasing with an increase in each of the two factors. The effects of other reaction parameters, such as the N/Pt mole ratio in the complex, solvents and reaction time, etc., on the hydrogenation of m-xylene were also studied. The Si-N-Pt catalyst is very stable in reaction and turnover numbers amount to 520 in 70 hr.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 451-458 
    ISSN: 0006-3592
    Keywords: immobilized glucose isomerase ; substrate protection ; reactor analysis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effect of substrate protection on enzyme deactivation was studied in a differential bed and a packed bed reactor using a commercial immobilized glucose isomerase (Swetase, Nagase Co.). Experimental data obtained from differential bed reactor were analyzed based on Briggs-Haldane kinetics in which enzyme deactivation accompanying the protection of substrate was considered. The deactivation constant of the enzyme-substrate complex was found to be about half of that of the free enzyme. The mathematical analysis describing the performance of a packed bed reactor under the considerations of the effects of substrate protection, diffusion resistance, and enzyme deactivation was studied. The system equations for the packed bed reactor were solved using an orthogonal collocation method. The presence of substrate protection and the diffusion effect within the enzyme particles resulted in an axial variation of effectiveness factor, ηD, along the length of the packed bed. The axial distribution profile of ηD was found to be dependent on the operation temperature, Based on the effect of substrate protection, a better substrate feed policy could be theoretically found for promoting productivity in long-term operation. © 1993 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Das Kristallisationsverhalten von Polyetheretherketon (PEEK) wurde mit Hilfe der Differentialkalorimetrie (DSC) untersucht. Mit der Erhöhung der Kristallinität verschiebt sich die Glastemperatur zu höheren Temperaturen. Hitzebehandeltes PEEK zeigt Doppelpeaks in der DSC-Kurve, was für PEEK charakteristisch ist. Diese Doppelpeaks werden, je nach den Bedingungen der Hitzebehandlung, durch die Bildung unvollständiger Kristallstrukturen hervorgerufen.
    Notes: The crystallization behavior of polyetheretherketone (PEEK) was investigated by differential scanning calorimetry (DSC). The glass transition temperature of PEEK shifts to higher temperatures with an increase in crystallinity. Heat-treated PEEK showed double peaks in their DSC curves, which is a characteristic phenomenon of PEEK. These double peaks were caused by the formation of incomplete crystal structures according to the conditions of heat-treatment.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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