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  • 1
    Electronic Resource
    Electronic Resource
    Temporal and spatial self-organisation in catalysis at single crystal surfaces (1991)
    Springer
    Catalysis letters 9 (1991), S. 219-230 
    Details
    ISSN: 1572-879X
    Keywords: Oscillatory catalytic reactions ; spatial differences in surface concentrations of reactants ; carbon monoxide oxidation on Pt(110)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The elementary steps underlying the mechanism of a catalytic reaction are also responsible for its rate under steady-state conditions. In special cases the rate will no longer be stationary, but may become oscillatory or even chaotic. These phenomena have to be ascribed to the nonlinear character of the coupled differential equations modelling the temporal behavior of the surface concentrations of the reacting species. As a consequence, these concentrations may also exhibit spatial differences, even on ana priori uniform single crystal surface, leading to spatiotemporal patterns such as propagating and standing waves as well as ‘chemical’ turbulence. Experimental evidence for these effects is presented for a particular system, the oxidation of CO on a Pt(110) surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00773180
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Microstructure of the activated industrial ammonia synthesis catalyst (1991)
    Springer
    Catalysis letters 11 (1991), S. 19-31 
    Details
    ISSN: 1572-879X
    Keywords: Ammonia synthesis ; iron catalyst ; surface characterization ; promoter effects ; nitrides ; ion scattering spectroscopy ; XPS ; HRTEM
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Industrial doubly-promoted iron catalysts and model systems of singly-promoted K- and Al-iron catalysts were characterised by their catalytic performance at 1 bar pressure. The relevance of bulk nitrogen for catalytic performance is shown. The catalysts were also activated in an in-situ reaction chamber of a He-ion scattering spectrometer (ISS) and their top atomic layer elemental composition was determined after they had reached similar performance as in the microreactor tests. The bulk microstructure of these samples was investigated by high resolution transmission electron microscopy (TEM) and microdiffraction. All evidence indicates that small highly crystalline α-Fe platelets act as active phase. Their surfaces are covered to a large extent by promotor compounds which are partly present as poorly crystalline aggregates with iron oxide leaving only a small fraction of elemental iron directly exposed to the gas phase. The intimate contact between iron crystals and promoters particles prevents recrystallisation and is the key to the understanding of the structural stability of the catalyst system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00866897
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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