Oxygen step-response experiments for methane oxidation over Pd/Al2O3: An in situ XAFS study

Nilsson, Jan-Olof; Carlsson, Per-Anders; Martin, Natalia; Velin, Peter; Meira, Débora Motta; Grönbeck, Henrik; Skoglundh, Magnus

doi:10.1016/j.catcom.2018.02.011

Cited by 13 publications

(21 citation statements)

References 17 publications

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“…[16,32,33] As can be seen, when 10 % H 2 O is introduced (t = 0.5 h) to the lean CH 4 /O 2 mixture, the methane conversion drops for both γ-Al 2 O 3 and the hydrophobic ZSM-5 supported palladium, present as PdO particles under prevailing conditions. [34][35][36] The drop is considerably more severe for the alumina catalysts, signifying a higher sensitivity towards water in line with previous works. [6] When water is removed from the feed (t = 24.5 h), the conversion is rapidly restored nearly in full for the ZSM-5 catalysts whereas for the alumina catalysts it is only partially recovered.…”

supporting

confidence: 89%

“…The oxidation kinetics includes a rapid surface oxidation evidenced by the nearly stepwise increase in WLI at first, followed by a slower deep oxidation reflected by the asymptotic increase in WLI in line with previous results. [36] As a function of time on stream, the more dispersed catalysts reach higher WLIs. When O 2 is switched off, both CH 4 -TOF and WLI drop for all samples reflecting a rapid extinction of the methane oxidation reaction and fast reduction of the PdO particles.…”

Section: Sample Idmentioning

confidence: 98%

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Hampered PdO Redox Dynamics by Water Suppresses Lean Methane Oxidation over Realistic Palladium Catalysts

et al. 2021

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By use of operando spectroscopies under cycling reaction conditions, water is shown to hamper the redox dynamics of realistic palladium oxide nanoparticles dispersed onto alumina and hydrophobic zeolite supports thereby lowering the activity for total oxidation of methane. Water adsorption forms hydroxyl ad‐species that block the methane and oxygen dissociation and seem to prevent lattice oxygen to take part in the methane oxidation. The main catalytic action is thus proposed to shift from the Mars‐van Krevelen mechanism in dry conditions to a slower route that relies on Langmuir‐Hinshelwood type of steps in wet conditions. This key finding has clear implications on catalyst design for low‐temperature gas combustion emission control.

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confidence: 89%

Section: Sample Idmentioning

confidence: 98%

Hampered PdO Redox Dynamics by Water Suppresses Lean Methane Oxidation over Realistic Palladium Catalysts

et al. 2021

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“…This means that, above 300 • C, the palladium is completely oxidized. The bulk oxidation of the 6 nm Pd nanoparticles in the oxidation of methane was previously observed by in situ XANES, but the temperature of the full oxidation of palladium was above 400 • C that is higher than in our case [39]. This could be due to the Pd 0 /Pd 2+ equilibrium depending not only the reaction condition (temperature and partial pressure of oxygen), but also the particle size.…”

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confidence: 41%

Atomic Structure of Pd-, Pt-, and PdPt-Based Catalysts of Total Oxidation of Methane: In Situ EXAFS Study

et al. 2021

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In this study, 3%Pd/Al2O3, 3%Pt/Al2O3 and bimetallic (1%Pd + 2%Pt)/Al2O3 catalysts were examined in the total oxidation of methane in a temperature range of 150–400 °C. The evolution of the active component under the reaction conditions was studied by transmission electron microscopy and in situ extended X-ray absorption fine structure (EXAFS) spectroscopy. It was found that the platinum and bimetallic palladium-platinum catalysts are more stable against sintering than the palladium catalysts. For all the catalysts, the active component forms a “core-shell” structure in which the metallic core is covered by an oxide shell. The “core-shell” structure for the platinum and bimetallic palladium-platinum catalysts is stable in the temperature range of 150–400 °C. However, in the case of the palladium catalysts the metallic core undergoes the reversible oxidation at temperatures above 300 °C and reduced to the metallic state with the decrease in the reaction temperature. The scheme of the active component evolution during the oxidation of methane is proposed and discussed.

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“…The PdO phase is the catalytic active phase under lean conditions once the oxide is well developed. [12][13][14] In contrast, for monometallic platinum catalysts, the oxidation of methane over platinum is inhibited by oxygen making palladium the element of choice in applications with oxygen excess. [15][16][17] The methane oxidation over palladium-alumina formulations is known to be inhibited by water present in the combustion exhaust and/or generated by the complete methane oxidation reaction itself.…”

Section: Introductionmentioning

confidence: 99%

Palladium dispersion effects on wet methane oxidation kinetics

Velin

Florén

Skoglundh

et al. 2020

Catal. Sci. Technol.

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Oxygen step-response experiments for methane oxidation over Pd/Al2O3: An in situ XAFS study

Cited by 13 publications

References 17 publications

Hampered PdO Redox Dynamics by Water Suppresses Lean Methane Oxidation over Realistic Palladium Catalysts

Hampered PdO Redox Dynamics by Water Suppresses Lean Methane Oxidation over Realistic Palladium Catalysts

Atomic Structure of Pd-, Pt-, and PdPt-Based Catalysts of Total Oxidation of Methane: In Situ EXAFS Study

Palladium dispersion effects on wet methane oxidation kinetics

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