Oscillatory oxidation of CO over Pt, Pd and Ir catalysts: Theory

Sales, B. C.; Turner, J. E.; Maple, M. B.

doi:10.1016/0039-6028(82)90692-6

Cited by 300 publications

(117 citation statements)

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“…They have found that the spontaneous oscillations during the oxidation of CO over Rh/Al 2 O 3 catalysts are due to the dissociation of CO followed by the subsequent adsorption and combustion of atomic carbon. The oxidation-reduction mechanism, which is also referred to as the STM mechanism, was developed by Sales, Turner, and Maple [58] in the early 1980s for the explanation of kinetic oscillations in the oxidation of CO on polycrystalline Pt, Pd, and Ir at near atmospheric pressure.…”

Section: Discussionmentioning

confidence: 99%

Evolution of self-sustained kinetic oscillations in the catalytic oxidation of propane over a nickel foil

Каичев

Teschner

Saraev

et al. 2016

Journal of Catalysis

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The evolution of self-sustained reaction-rate oscillations in the catalytic oxidation of propane over a nickel foil has been studied in situ using X-ray photoelectron spectroscopy coupled with on line mass spectrometry and gas chromatography. Changes in the effective surface area and in the catalyst morphology under reaction conditions have been examined by scanning electron microscopy and a krypton adsorption technique. It is shown that the regular kinetic oscillations arise under oxygen-lean conditions. CO, CO 2 , H 2 , H 2 O, and propylene are detected as products.The conversion of propane oscillates in a range from 1% to 23%. During the half-periods with high activity, the main reaction pathway is the partial oxidation of propane: selectivity toward CO achieves 98%. In contrast, during the half-periods with low activity, the reaction proceeds through three competitive pathways: the partial oxidation of propane, the total oxidation of propane, and the dehydrogenation of propane to propylene. The driving force for the selfsustained kinetic oscillations is the periodic reoxidation of nickel. According to the Ni2p and O1s core-level spectra measured in situ, the high-active catalyst surface is represented by metallic nickel, whereas during the inactive half-periods the catalyst surface is covered with a thick layer of NiO. The intensity of O1s spectra follows the oscillations of O 2 in the gas phase during the oxidation of propane. It is found that during the induction period before the regular oscillations appear, a rough and porous structure develops because of strong reconstruction of the catalyst surface. The thickness of the reconstructed layer is approximately 10-20 µm. This process is accompanied with at least an 80-fold increase in the effective surface area compared with a clean, non-treated nickel foil, which undoubtedly leads to a drastic increase in the number of active sites. We believe that it is the main reason for the induction period always being  Corresponding author.E-mail address: vvk@catalysis.ru (V.V. Kaichev) 2 observed before the appearance of self-sustained oscillations in the catalytic oxidation of light hydrocarbons over catalysts with a low specific surface area (single crystals, foils, or wires).Moreover, without such reconstruction, the oscillations cannot arise due to low activity of such catalysts.

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Section: Discussionmentioning

confidence: 99%

Evolution of self-sustained kinetic oscillations in the catalytic oxidation of propane over a nickel foil

Каичев

Teschner

Saraev

et al. 2016

Journal of Catalysis

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“…This could correspond to an oxidation of the metal surface layer, e.g. by formation of subsurface oxygen as was suggested by Sales et al (1982). This step is not assumed to be a pure buffer step because a reaction of subsurface oxygen with adsorbed ethanol and acetaldehyde, steps (10) and (11) in the reaction path STSO in Table 1, is also allowed.…”

Section: Model Constructionmentioning

confidence: 95%

“…Bifurcation phenomena, such as multiple steady-states (R~zon and Schmitz,1987;Zhdanov and Kasemo, 1994), autonomous oscillations ( Gray and Scott, 1990) or chaos ( Scott, 1991) are well documented for heterogeneous catalytic reactions. In the absence of heat and/or mass transport limitations such phenomena have to be caused by purely chemical feedback features such as autocatalysis.…”

Section: Introductionmentioning

confidence: 99%

“…The upper steady-state was reached by a reductive start-up procedure while the two lower steady-states required an oxidative start-up. The existence of steady-state multiplicity is believed to be rather common for selective oxidations and hydrogenations by noble metals in the liquid phase.Bifurcation phenomena, such as multiple steady-states (R~zon and Schmitz,1987;Zhdanov and Kasemo, 1994), autonomous oscillations ( Gray and Scott, 1990) or chaos ( Scott, 1991) are well documented for heterogeneous catalytic reactions. In the absence of heat and/or mass transport limitations such phenomena have to be caused by purely chemical feedback features such as autocatalysis.…”

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confidence: 99%

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Kinetic modelling of multiple steady-states for the oxidation of aqueous ethanol with oxygen on a carbon supported platinum catalyst

Jelemenský

Kuster

Marin

1996

Chemical Engineering Science

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-Multiple steady-states data were used for the construction of a kinetic model for the oxidation of aqueous ethanol with oxygen on a carbon supported platinum catalyst. A model, incorporating reversible creation of oxygen adatoms on the catalyst surface from surface hydroxyl as well as reversible formation of subsurface oxygen from oxygen adatoms, couid describe quantitatively all the observations. It was essential that the reaction rate coefficients for the formation of atomic and subsurface oxygen strongly depend on the corresponding degrees of coverage introducing positive and negative feedback features. INTRODUCTIONThe selective catalytic oxidation of alcohols and carbohydrates with dioxygen has received considerable attention in the recent past ( Mallat and Balker, 1994). Supported noble metals are the favourite catalysts. The reaction can be performed selectively at relatively mild conditions i.e. in aqueous media at a pH around 7 and at temperatures around 300 K.The major bottleneck for the commercial application consists in so-called catalyst deactivation. Several causes have been put forward for the latter ( Schuurman et al., 1992b;Mallat and Baiker, 1994;Vleeming et al., 1994). There is evidence for well known deactivation mechanisms such as metal dissolution and/or sintering (Schuurman et al., 1992b) and coverage of active sites by side or intermediate products of the desired reaction ( Mallat and Baiker, 1994). A phenomenon more specific to the considered type of reactions has also been suggested. It is referred to as overoxidation of the metal surface. The term stems from the observation that the loss in activity occurs in parallel with an increase of the catalyst potential (Vleeming et al., 1994).Recently steady-state multiplicity of the selective oxidation rate of aqueous ethanol over a platinum on carbon catalyst has been reported (Jelemensky et al., 1995). Up to three stable steady-state rates could be established over a feed ethanol concentration range from 300 to 400 mol m 3 in a continuous flow stirred tank reactor. The upper steady-state was reached by a reductive start-up procedure while the two lower steady-states required an oxidative start-up. The existence of steady-state multiplicity is believed to be rather common for selective oxidations and hydrogenations by noble metals in the liquid phase.Bifurcation phenomena, such as multiple steady-states (R~zon and Schmitz,1987;Zhdanov and Kasemo, 1994), autonomous oscillations ( Gray and Scott, 1990) or chaos ( Scott, 1991) are well documented for heterogeneous catalytic reactions. In the absence of heat and/or mass transport limitations such phenomena have to be caused by purely chemical feedback features such as autocatalysis. The observations of Jelemensky et al. (1995) were free of transport limitations.The present paper concerns the development of an intrinsic kinetic model for the platinum catalyzed selective oxidation of ethanol which allows a quantitative description of the complete set of data reported by Jelemensky et al. (...

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“…The period of the oscillation is almost 22 min whereas the residence time in the reactor is approximately 1 s. Apparently, some slow and large scale phenomenon is taking place on the surface (or in the reactor) at a completely different timescale than the surface reaction itself. The model of equation 5.8 does not show these oscillations, though attempts have been done to use additional slow steps to explain this feature in literature [119,120].…”

Section: Oscillatory Behaviormentioning

confidence: 99%