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  • 1
    Electronic Resource
    Electronic Resource
    Kinetic-transport models and the design of catalysts and reactors for the oxidative coupling of methane (1993)
    Springer
    Catalysis letters 19 (1993), S. 167-180 
    Details
    ISSN: 1572-879X
    Keywords: Reaction-transport ; catalyst design ; reactor design ; methane coupling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The design of catalytic pellets and reactors using detailed kinetic-transport models is illustrated for the oxidative coupling of methane to form ethane and ethylene. Oxygen sieving within diffusion-limited pellets and staged oxygen injection reactors increase C2 selectivity by inhibiting full oxidation homogeneous pathways that lead to CO and CO2 products. Our simulations suggest that high densities of surface sites with kinetics that depend weakly on oxygen concentration are required to benefit from oxygen-sieving catalyst and reactor schemes. These sites favor beneficial surface activation processes even at the low oxygen concentrations present within staged injection reactors and diffusion-limited pellets. Controlled introduction of stoichiometric oxygen reactants leads to C2 yields as high as 50%; the reactions, however, occur at much slower rates and require much greater reactor volumes than in conventional cofeed reactors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00771752
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  • 2
    Electronic Resource
    Electronic Resource
    A simple correlation for predicting effective diffusivities in immobilized cell systems (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 49 (1996), S. 223-227 
    Details
    ISSN: 0006-3592
    Keywords: immobilized cells ; diffusivity measurement ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A simple correlation method has been developed to predict effective diffusivities of small molecules in heterogeneous materials such as immobilized cell systems. This correlation uses a single diffusivity measurement at one cell volume fraction to predict diffusivities for any other volume fraction of cell. The method has been applied to 20 sets of published diffusivity measurements in immobilized cell systems and accurately predicts affective diffusivities of molecules for the full range of cell fractions. It may also be used to predict effective diffusivities in heterogeneous materials in which the diffusivity of a molecule in each phase and the volume fraction of each phase are known. © 1996 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260490202
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  • 3
    Electronic Resource
    Electronic Resource
    Diffusion in heterogeneous media: Application to immobilized cell systems (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 691-700 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Transport of small molecules in heterogeneous materials can be an important factor in many engineering and biological applications. This study focuses on the diffusion of cellular nutrients in an immobilized cell system. A Monte Carlo simulation technique is used to describe the diffusion of small molecules in a variety of simulated cellular structures. Diffusivity predictions are in close agreement with experimental values as well as with theoretical bounds reported in the literature. It is revealed that effective diffusivities are highly dependent on the diffusivities of the species in the various phases and on the volume fraction of cells. The spatial arrangement of the cells, however, has no apparent effect on the predicted diffusivity for the range of conditions investigated.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410326
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