What drives spontaneous oscillations during CO oxidation using O2 over supported Rh/Al2O3 catalysts?

Figueroa, Santiago; Newton, Mark A.

doi:10.1016/j.jcat.2014.01.006

Cited by 26 publications

(13 citation statements)

References 54 publications

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“…The mechanism is based on the combination of the Langmuir-Hinshelwood surface reaction, a slow catalyst deactivation via the carbon deposition, and a reactive regeneration of these deactivated sites by oxygen. More recently, Figueroa and Newton [57] have shown that this mechanism describes well the oscillatory behavior of the oxidation of CO over rhodium at atmospheric pressure. 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.…”

Section: Discussionmentioning

confidence: 66%

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: 66%

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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“…In addition, oscillation is a common and undesirable behavior present in the Pd-based catalysts for CH 4 combustion under CH 4 -rich conditions: e.g., CBM deoxygenation. − Although the oscillation generally originates from chemical mechanisms, such as the alternating oxidation–reduction of the catalyst surface, ,− reconstruction of the active surface, , and the strong adsorption of reactants, intermediates, or products, ,, it can be modified by the enhancement of heat transfer and diffusion in the catalyst bed. − It has been reported that CeO 2 modification of Pd/Al 2 O 3 (denoted as Pd-CeO 2 /Al 2 O 3 ) weakened the undesirable reaction oscillation as a result of the stabilization of the Pd chemical state due to the oxygen storage capability of CeO 2 . The Pd@CeO 2 core–shell structure maximizes the active interfacial area between Pd and CeO 2 , thereby further suppressing the oscillatory behavior in the CBM deoxygenation via methane combustion.…”

Section: Introductionmentioning

confidence: 99%

High-Performance PdNi Nanoalloy Catalyst in Situ Structured on Ni Foam for Catalytic Deoxygenation of Coalbed Methane: Experimental and DFT Studies

Zhang

et al. 2016

ACS Catal.

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A Ni-foam-structured PdNi nanoalloy catalyst engineered from nano- to macro-scales has been successfully fabricated for the catalytic deoxygenation of coalbed methane (CBM). The catalyst was obtainable by embedment of Pd nanoparticles onto Ni-foam substrate via a galvanic exchange reaction method and subsequent in situ activation in the reaction, which was active at low temperature, selective (no CO formation), and oscillation free in this CH4-rich catalytic combustion process. Special Pd@NiO (Pd nanoparticles partially wrapped by tiny NiO fragments) ensembles were formed in the galvanic deposition stage and could merely be transformed into PdNi nanoalloys in the real reaction stream at elevated temperatures (e.g., 450 °C or higher). Density functional theory (DFT) calculations were carried out to reveal the role of Ni decoration at Pd in PdNi nanoalloy catalyst for the CBM deoxygenation. By nature, the Pd–Ni alloying modified the electronic structure of surface Pd and led to a decrease in the O adsorption energy, which can be taken as the activity descriptor for the CBM deoxygenation. A reaction kinetic study indicated that the Ni decoration at Pd by Pd–Ni alloying lowered the apparent activation energy in comparison to the pristine Pd catalyst, while leading to an increase of the reaction order of O2 from −0.6 at Pd catalyst to −0.3. The foam-structured PdNi nanoalloy catalyst thus offered enhanced low-temperature activity and the elimination of oscillating phenomena as the result of a transient balance obtained between the cycles of O2 adsorption/activation and CH4 oxidation.

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“…However, as is all too evident from the literature, axial gradients in temperature, structure, and speciation can legitimately arise as a consequence of the chemistry under study. 12,13,20,[36][37][38][39][40] As such, though easily achieved, this method may only be indicative of unwanted thermal gradients in certain cases (such as we have demonstrated for Cu/ MOR in the activation of methane).…”

Section: Catalysis Science and Technologymentioning

confidence: 98%

On isothermality in some commonly used plug flow reactors for X-ray based investigations of catalysts

Newton

Checchia

Knorpp

et al. 2019

Catal. Sci. Technol.

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What drives spontaneous oscillations during CO oxidation using O2 over supported Rh/Al2O3 catalysts?

Cited by 26 publications

References 54 publications

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

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

High-Performance PdNi Nanoalloy Catalyst in Situ Structured on Ni Foam for Catalytic Deoxygenation of Coalbed Methane: Experimental and DFT Studies

On isothermality in some commonly used plug flow reactors for X-ray based investigations of catalysts

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