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  • 1
    Electronic Resource
    Electronic Resource
    Effects of reactant composition and nonuniformities on temperature fronts (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 1896-1903 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Stationary and spatially oscillating temperature fronts separating regions with high and low temperatures (amplitudes up to 120 K) formed during the atmospheric oxidation of carbon monoxide on a Pd on alumina ring kept in a mixed reactor. The sharp fronts bounded either one or two low temperature regions. The transition from stationary to spatially oscillating fronts occurred at a feed CO/O2 concentration ratio close to 2.0 and was independent of the reactor temperature. The net rate of local heat generation on the ring was nonuniform leading to angular variation of the temperature of the ignited state. Front motions were affected by both the nonuniformity of the system and the interaction between the catalyst and the ambient gas. The two fronts bounding a low temperature region usually moved at different velocities and their velocities increased with increasing oxygen concentration. In most cases the two fronts did not move in phase, but sometimes they moved in tandem generating a back-and-forth pulse motion. The spatial amplitude of the oscillations decreased as the slope of the net heat generation activity became steeper. The spatial variation of the standard deviation of the temperature was helpful in assessing the dynamics of the oscillating fronts. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.474540
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  • 2
    Electronic Resource
    Electronic Resource
    Complex oscillations and global coupling during the catalytic oxidation of CO (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 6375-6386 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Rate oscillations during heterogeneous catalytic reactions often display self-similar mixed-mode oscillations that have also been found in various other experimental systems. Spatially nonuniform behavior is revealed by monitoring the surface temperature during complex oscillations in the kinetic regime of the CO oxidation on a Pd supported catalyst at atmospheric pressure. The experimental results demonstrate the influence of global coupling via the gas phase concentration of the deficient component. In addition, the local autonomous frequency appears to be spatially nonuniform. A simple discrete model, a set of globally coupled relaxation oscillators with a frequency distribution, captures qualitatively the experimentally observed behavior. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.471299
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  • 3
    Electronic Resource
    Electronic Resource
    Temperature patterns on a hollow cylindrical catalytic pellet (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Chaos 9 (1999), S. 36-42 
    Details
    ISSN: 1089-7682
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The atmospheric oxidation of a mixture containing 6 vol % carbon monoxide was carried out on a hollow cylindrical catalytic pellet. The catalyst was held in a conical reactor which enabled simultaneous measurement of the temperature patterns on the top and side of the pellet by an IR imager. Upon a decrease in the reactor temperature the fully ignited, high temperature state of the pellet is transformed to a nonuniform one with temperature fronts separating high and low temperature regions. The transition and the resulting states are rather intricate and are strongly influenced by the nonuniformity of the catalyst and the transport to and from it, as well as the global coupling, which stabilizes temperature fronts and patterns, which would not exist in its absence. Intricate pulse splitting and extinction were observed both on the top and the side of the pellet. Highly irregular motions and conversions were obtained following a decrease in the reactor temperature. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.166378
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  • 4
    Electronic Resource
    Electronic Resource
    Periodic perturbation of a drifting heterogeneous catalytic system (1993)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 97 (1993), S. 11724-11730 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100147a028
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  • 5
    Electronic Resource
    Electronic Resource
    Temperature Oscillations Characterized by An Overall Activation Energy (2000)
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 995-1003 
    Details
    ISSN: 1572-8943
    Keywords: overall activation energy ; oxidations ; thermokinetic oscillations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Temperature oscillations obtained during the heterogeneous catalytic oxidation of ethanol on Pd-Al2 O3 in a dynamic calorimeter were characterized by an overall activation energy. This parameter was determined by a non-isothermal kinetic method using the minimum and maximum values of the oscillations temperature. Using the bifurcation diagram with the oxygen as a bifurcation parameter an E value between 27.6 and 28.2 kJ mol-1 was obtained. With ethanol as bifurcation parameter the E values lies between 28.1 and 31.1 kJ mol-1 for 3.5 to 4.0 vol% ethanol and between 25.8 and 27.6 kJ mol-1 for 4.0 to 4.7 vol% ethanol. These results have been discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010131616337
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  • 6
    Electronic Resource
    Electronic Resource
    Oscillating temperature pulses during CO oxidation on a Pd/Al2O3 ring (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1519-1528 
    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: Back-and-forth-moving temperature fronts separating regions with high and low temperatures (amplitudes up to 100 K) formed on a Pd on alumina ring during the atmospheric oxidation of carbon monoxide. The back-and-forth front movement reflects the intrinsic nonuniformity of the catalytic system and the impact of global coupling. The ignition and extinction fronts usually moved at different velocities, in agreement with theoretical predictions. Complex spatiotemporal patterns were observed due to small-amplitude temperature fronts that moved on the high-temperature region at a much higher velocity than the high-amplitude fronts. The qualitative motion features were affected by changes in the excess oxygen concentration. The nonuniform states existed mainly for feed conditions for which the only uniform state was an extinguished one.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430615
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