Operando resonance Raman spectroscopic characterisation of the oxidation state of palladium in Pd/γ-Al<sub>2</sub>O<sub>3</sub>catalysts during the combustion of methane

Demoulin, Olivier; Navez, Michaël; Gaigneaux, Éric M.; Ruíz, Patricio; Mamede, Anne-Sophie; Granger, Pascal; Payen, Edmond

doi:10.1039/b305817b

Cited by 67 publications

(65 citation statements)

References 34 publications

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“…The extent of formation of surface complexes is determined by the morphology of underlying bulk Pd metal and oxide phases which is, in turn, influenced by the thermal history of the catalyst [22]. Based on our previous data [42], we agree with that view and suggest that this activation phenomenon reflects structural changes, which allow the progressive covering of the palladium particles with highly reactive oxygen species, coming from the dissociative adsorption of O 2 . This process could be favored by the development of preferential planes onto which such species are more easily produced and/or stabilized, but it would principally result from the formation of a more flexible structure where the lattice oxygen can migrate (by diffusion) more easily.…”

Section: Resultssupporting

confidence: 73%

“…Previously, we have shown that high performances in methane combustion of a Pd/c-Al 2 O 3 catalyst are related to the presence of an external layer of highly active oxygen species on the surface of the PdO particles [42]. The development of such a layer would ensure an optimal activity to the Pd/c-Al 2 O 3 catalyst, as detailed elsewhere (Demoulin et al, submitted).…”

Section: Resultsmentioning

confidence: 95%

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The Activation of a Pd/γ-alumina Catalyst During Methane Combustion: Investigation of the Phenomenon and of Potential Causes

2005

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Section: Resultssupporting

confidence: 73%

Section: Resultsmentioning

confidence: 95%

The Activation of a Pd/γ-alumina Catalyst During Methane Combustion: Investigation of the Phenomenon and of Potential Causes

2005

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“…Depending on the reaction conditions, Pd is known to form PdO in supported catalysts during reaction conditions [12]. The oxidation of a Pd crystallite is not restricted to just the surface region of the metal particles but can reach several atomic layers [13], thus relatively large amounts of oxygen can be incorporated into the Pd structure.…”

Section: Discussionmentioning

confidence: 99%

Methane oxidation over Pt/Al2O3 and Pd/Al2O3 catalysts under transient conditions

2007

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We communicate experimental results for the oxidation of methane by oxygen over alumina supported Pd and Pt monolith catalysts under transient conditions. Temperature programmed reaction (TPReaction) and reactant pulse-response (PR) experiments have been performed, using a continuous gas-flow reactor equipped with a downstream mass spectrometer for gas phase analysis. Special attention was paid to the influence of gas composition changes, i.e., O 2 and H 2 pulsing, respectively, on the methane conversion. For Pt/Al 2 O 3 oxygen pulsing can significantly increase the methane conversion which can be even further improved by pulsing hydrogen instead. Such transient effects are not observed for the Pd/Al 2 O 3 catalyst for which instead constantly lean conditions is beneficial. Our results suggest that under lean conditions Pd and Pt crystallites may undergo bulk-and partial (surface oxide formation) oxidation, respectively, which for Pd results in more active surfaces, while for Pt the activity is reduced. The latter seems to connect to a lowering of the ability to dissociate methane.

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“…23,24 The 644 cm À1 is ascribed to new palladium oxide species. 25,26 CeO 2 has a special property of changing oxidation state of lattice Ce between Ce III and Ce IV through oxygen release and storage. 27 The intensity increase of the 556 cm À1 peak means that lattice Ce III content in the CeO 2 support increased.…”

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confidence: 99%

Catalytic Ozonation of Oxalate with a Cerium Supported Palladium Oxide: An Efficient Degradation Not Relying on Hydroxyl Radical Oxidation

Zhang

Croué

2011

Environ. Sci. Technol.

154

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The cerium supported palladium oxide (PdO/CeO2) at a low palladium loading was found very effective in catalytic ozonation of oxalate, a probe compound that is difficult to be efficiently degraded in water with hydroxyl radical oxidation and one of the major byproducts in ozonation of organic matter. The oxalate was degraded into CO2 during the catalytic ozonation. The molar ratio of oxalate degraded to ozone consumption increased with increasing catalyst dose and decreasing ozone dosage and pH under the conditions of this study. The maximum molar ratio reached around 1, meaning that the catalyst was highly active and selective for oxalate degradation in water. The catalytic ozonation, which showed relatively stable activity, does not promote hydroxyl radical generation from ozone. Analysis with ATR-FTIR and in situ Raman spectroscopy revealed that 1) oxalate was adsorbed on CeO2 of the catalyst forming surface complexes, and 2) O3 was adsorbed on PdO of the catalyst and further decomposed to surface atomic oxygen (*O), surface peroxide (*O2), and O2 gas in sequence. The results indicate that the high activity of the catalyst is related to the synergetic function of PdO and CeO2 in that the surface atomic oxygen readily reacts with the surface cerium-oxalate complex. This kind of catalytic ozonation would be potentially effective for the degradation of polar refractory organic pollutants and hydrophilic natural organic matter.

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Operando resonance Raman spectroscopic characterisation of the oxidation state of palladium in Pd/γ-Al₂O₃catalysts during the combustion of methane

Cited by 67 publications

References 34 publications

The Activation of a Pd/γ-alumina Catalyst During Methane Combustion: Investigation of the Phenomenon and of Potential Causes

The Activation of a Pd/γ-alumina Catalyst During Methane Combustion: Investigation of the Phenomenon and of Potential Causes

Methane oxidation over Pt/Al2O3 and Pd/Al2O3 catalysts under transient conditions

Catalytic Ozonation of Oxalate with a Cerium Supported Palladium Oxide: An Efficient Degradation Not Relying on Hydroxyl Radical Oxidation

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Operando resonance Raman spectroscopic characterisation of the oxidation state of palladium in Pd/γ-Al2O3catalysts during the combustion of methane

Cited by 67 publications

References 34 publications

The Activation of a Pd/γ-alumina Catalyst During Methane Combustion: Investigation of the Phenomenon and of Potential Causes

The Activation of a Pd/γ-alumina Catalyst During Methane Combustion: Investigation of the Phenomenon and of Potential Causes

Methane oxidation over Pt/Al2O3 and Pd/Al2O3 catalysts under transient conditions

Catalytic Ozonation of Oxalate with a Cerium Supported Palladium Oxide: An Efficient Degradation Not Relying on Hydroxyl Radical Oxidation

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Operando resonance Raman spectroscopic characterisation of the oxidation state of palladium in Pd/γ-Al₂O₃catalysts during the combustion of methane