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  • 1990-1994  (2)
  • ammonia synthesis  (1)
  • carbon monoxide oxidation on Pt(110)  (1)
  • 1
    Electronic Resource
    Electronic Resource
    The dissociative adsorption of N2 on a multiply promoted iron catalyst used for ammonia synthesis: a temperature-programmed desorption study (1994)
    Springer
    Catalysis letters 24 (1994), S. 317-331 
    Details
    ISSN: 1572-879X
    Keywords: Nitrogen adsorption ; N2 TPD ; iron-based catalyst ; ammonia synthesis ; microkinetic analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The temperature-programmed desorption (TPD) of N2 from a multiply promoted iron catalyst used for ammonia synthesis has been studied in a microreactor system at atmospheric pressure. From TPD experiments with various heating rates a preexponential factorA = 2 × 109 molecules/site s and an activation energyE = 146 kJ/mol was derived assuming second-order desorption. The observed dependence of the TPD peak shapes on the heating rates indicated the influence of readsorption of N2 in agreement with the results obtained for various initial coverages. Simulating the N2 TPD curves using the model by Stoltze and Nørskov revealed that the calculated TPD curves were not influenced by the molecular precursor to desorption. However, the calculated rate of readsorption was found to be overestimated at high coverage compared with the experimental results. A coverage-dependent net activation energy for dissociative chemisorption (E*) was introduced as the simplest assumption rendering the dissociative chemisorption of N2 activated at high coverage. The best fit of the experimental data yieldedE* = (−15+30θ) kJ/mol using only a single type of atomic nitrogen species. These findings are in satisfactory agreement with the parameters underlying the Stoltze-Nørskov model for the kinetics of ammonia synthesis as well as with the data reported for Fe(111) single crystal surfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00811804
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    Paper (German National Licenses)
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  • 2
    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
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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