Oscillatory behaviour of catalytic properties, structure and temperature during the catalytic partial oxidation of methane on Pd/Al2O3

Kimmerle, Bertram; Baiker, Alfons; Grunwaldt, Jan‐Dierk

doi:10.1039/b924001b

Cited by 40 publications

(43 citation statements)

References 23 publications

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“…Next we exploit the exothermicity of CO oxidation (DH = À282 kJ/mol [73]) to identify the catalyst bed region directly responsible for the catalytic performance using IR thermography [28] to monitor the packed bed reactor. Spatially and time-resolved structural information on the catalyst was obtained from QEXAFS data recorded at different temperatures along the light-off curve with a small X-ray beam spot size.…”

Section: Resultsmentioning

confidence: 99%

“…However, this is in contradiction to surface scientific studies [63,64,73,74], modeling studies [75,76], the observation of a beneficial effect of H 2 during CO oxidation [76] and also to a very recent ETEM study which ascribed increased activity to metallic nanoparticles [54]. Moreover, structural heterogeneities along the catalyst bed were revealed lately, which were also observed during noble metal catalyzed partial oxidation of methane [28,77,78].…”

Section: Introductionmentioning

confidence: 90%

“…The next obvious step would be the correlation of catalytic activity and structural studies in a spatially resolved and time-resolved manner, which appears to be particularly attractive for oscillatory reactions. In principle, the combination of spatially resolved XAS with IR thermography would allow the correlation of effects on the macroscopic scale (temperature distribution) with dynamics on the microscopic scale (e.g., oxidation state) [26][27][28] and thus significantly improve the development of structureperformance relationships.…”

Section: Introductionmentioning

confidence: 99%

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Operando spatially and time-resolved X-ray absorption spectroscopy and infrared thermography during oscillatory CO oxidation

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 90%

Section: Introductionmentioning

confidence: 99%

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Operando spatially and time-resolved X-ray absorption spectroscopy and infrared thermography during oscillatory CO oxidation

Gänzler

Casapu

Boubnov

et al. 2015

Journal of Catalysis

Self Cite

117

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“…Recently, it has been confirmed directly by the results of in situ studies [25][26][27]. However, the reasons that initiate the appearance of these oscillations are not clear yet.…”

Section: Introductionmentioning

confidence: 86%

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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“…XAS has become a valuable technique for the structural characterization of heterogeneous catalysts under reaction conditions as high‐energy X‐rays feature a large penetration depth 69, 70. Operando XAS has allowed analyzing dynamic changes during the oscillatory oxidation of CO71 or partial oxidation of CH 4 72 uncovering in both cases strong changes in the oxidation state. Time resolution in the ms regime can be achieved using both dispersive EXAFS (DEXAFS, Turbo‐XAS)73 and quick‐EXAFS (including a continuously scanning monochromator) 74.…”

Section: Advancing the Characterization Methods: Following Dynamics mentioning

confidence: 99%

Future Challenges in Heterogeneous Catalysis: Understanding Catalysts under Dynamic Reaction Conditions

et al. 2016

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In the future, (electro‐)chemical catalysts will have to be more tolerant towards a varying supply of energy and raw materials. This is mainly due to the fluctuating nature of renewable energies. For example, power‐to‐chemical processes require a shift from steady‐state operation towards operation under dynamic reaction conditions. This brings along a number of demands for the design of both catalysts and reactors, because it is well‐known that the structure of catalysts is very dynamic. However, in‐depth studies of catalysts and catalytic reactors under such transient conditions have only started recently. This requires studies and advances in the fields of 1) operando spectroscopy including time‐resolved methods, 2) theory with predictive quality, 3) kinetic modelling, 4) design of catalysts by appropriate preparation concepts, and 5) novel/modular reactor designs. An intensive exchange between these scientific disciplines will enable a substantial gain of fundamental knowledge which is urgently required. This concept article highlights recent developments, challenges, and future directions for understanding catalysts under dynamic reaction conditions.

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Oscillatory behaviour of catalytic properties, structure and temperature during the catalytic partial oxidation of methane on Pd/Al2O3

Cited by 40 publications

References 23 publications

Operando spatially and time-resolved X-ray absorption spectroscopy and infrared thermography during oscillatory CO oxidation

Operando spatially and time-resolved X-ray absorption spectroscopy and infrared thermography during oscillatory CO oxidation

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

Future Challenges in Heterogeneous Catalysis: Understanding Catalysts under Dynamic Reaction Conditions

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