Stability of Pd-Pt catalysts in low-temperature wet methane combustion: Metal ratio and particle reconstruction

Nassiri, Hanieh; Hayes, Robert E.; Semagina, Natalia

doi:10.1016/j.ces.2018.04.028

Cited by 29 publications

(14 citation statements)

References 72 publications

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“…Thus, to achieve better durability, Pt is often incorporated into Pd catalysts, resulting in tolerance to H 2 O and sulfur. − Because of the different decomposition temperatures of PdO and PtO 2 , Pd remains in the PdO phase up to 800 °C in air, whereas the Pt is favored metallic phase under the same conditions. − Therefore, the active sites vary with reaction conditions where Pd and Pt show high activity under lean or rich conditions, respectively. − Contradictory results have also reported that Pt addition to Pd catalysts shows increased or decreased catalytic activity affected by different Pt/Pd compositions. Some studies reported that the incorporation of an appropriate amount of Pt into Pd results in significantly improved catalytic performance by maintaining the metallic Pd state even under lean conditions. ,,− …”

Section: Introductionmentioning

confidence: 99%

“…It is challenging to characterize the surface composition of Pt–Pd bimetallic catalysts and quantify each site precisely from mixed multiple phases (PdO, PdO x , metallic Pd, and metallic Pt). More critically, facile and fast reversible conversion between Pd and PdO occurs during the CH 4 oxidation reaction, making it even more difficult to characterize the catalytically relevant phases of Pt–Pd bimetallic catalysts. ,− , …”

Section: Introductionmentioning

confidence: 99%

“…More critically, facile and fast reversible conversion between Pd and PdO occurs during the CH 4 oxidation reaction, making it even more difficult to characterize the catalytically relevant phases of Pt−Pd bimetallic catalysts. 24,[32][33][34][35]39 In this work, we prepared a series of hydrothermally aged Pd and Pt−Pd bimetallic catalysts to investigate the catalytic CH 4 oxidation activity with respect to the surface composition of Pd or Pt−Pd bimetallic clusters. After oxidative pretreatment, the CH 4 oxidation activities of the Pd-based catalysts were screened at 300 °C.…”

Section: ■ Introductionmentioning

confidence: 99%

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CH₄ Oxidation Activity in Pd and Pt–Pd Bimetallic Catalysts: Correlation with Surface PdO_x Quantified from the DRIFTS Study

Jang

Lee

et al. 2021

ACS Catal.

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For Pd-based catalysts, facile and fast interconversion between Pd and PdO occurs continuously during the CH 4 oxidation reaction, which makes it challenging to determine active sites. Herein, we report that the amount of partially oxidized palladium (PdO x ) on the catalyst surface shows a linear correlation with the CH 4 oxidation activity in a series of Pd/Al 2 O 3 and Pt− Pd/Al 2 O 3 catalysts hydrothermally aged under commercially relevant conditions. We characterized the amount of surface PdO x through diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) using CO as a probe molecule. With careful consideration that the redox cycle of Pd particles occurs continuously during the CH 4 oxidation reaction, the Pd/Al 2 O 3 catalysts were reoxidized before obtaining the CO adsorption DRIFTS data to minimize the discrepancy between the catalytically relevant phases and the characterized surface composition. The IR spectra of CO adsorption on reoxidized Pd/Al 2 O 3 catalysts contain peaks at 2135−2145 cm −1 , which correspond to PdO x . The steady-state CH 4 oxidation activities at 300 °C increased proportionally with the normalized surface PdO x . Furthermore, Pt−Pd bimetallic catalysts also showed the same linear correlation between the surface PdO x and CH 4 oxidation activity irrespective of composition, preparation method, and support. Our results indicate that the surface PdO x plays a critical role in determining CH 4 oxidation activity rather than the electronic properties of Pd. Overall, we report a general correlation between the amount of surface PdO x and the steady-state CH 4 oxidation activities in various Pd-based catalysts. This work will greatly help in achieving the fundamental understanding of the CH 4 oxidation reaction on the PdO x surface and the further development of Pd-based catalysts for CH 4 oxidation with better activity.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

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CH₄ Oxidation Activity in Pd and Pt–Pd Bimetallic Catalysts: Correlation with Surface PdO_x Quantified from the DRIFTS Study

Jang

Lee

et al. 2021

ACS Catal.

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“…Considering the PdPt system, in the dry feed, Pt is blocked by oxygen, because the sticking coefficient of oxygen on Pt is 15 times higher than that for methane . In the lack of oxygen, Pt sites are free for methane activation, ,,, and as we showed earlier, , the PdPt system is significantly more active than Pd and Pt alone in the wet feed but less active than PdO in the dry feed. The water presence, thus, affects the contribution of Pt and Pd/PdO to methane activation via its temperature-dependent effect on oxygen mobility and oxygen exchange.…”

Section: Resultsmentioning

confidence: 75%

“…PdO is the dominant species in our defined “dry” feed (in the excess of local surface oxygen). In the wet feed, at the local oxygen deficit, metallic Pd and Pt sites prevail but metallic Pd alone was significantly less active than the PdPt combination, ,, indicating the dominant contribution of Pt active sites for methane activation in the lack of oxygen.…”

Section: Resultsmentioning

confidence: 97%

Kinetics of Low-Temperature Methane Oxidation over SiO₂-Encapsulated Bimetallic Pd–Pt Nanoparticles

Habibi

Semagina

Hayes

2018

Ind. Eng. Chem. Res.

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A kinetic study of lean methane combustion on a silica-encapsulated bimetallic Pd–Pt (1:1 molar ratio) catalyst at varying methane concentrations and temperatures and in the absence/presence of added water is presented. With dry feed, the kinetic behavior of the bimetallic catalyst is correlated using a previously reported rate expression that is first order in methane and negative one order in water. The model does not adequately correlate the conversion of wet lean CH4 combustion in the temperature range of 550 to 750 K. For wet conditions, an alternative mechanism is suggested that is based on the previous experimental observations of the prevailing chemical state of Pd in wet feed, the ability of Pt to activate methane in oxygen-deficient atmospheres, and the inhibitory effect of water on the support-mediated oxygen exchange. The corresponding rate expression successfully predicts the activity of the silica-encapsulated Pd–Pt catalyst with wet feed (5 vol % water) in the temperature range of 550 to 750 K. The study also evaluates the internal mass transfer across the silica shell. It is shown that for the catalysts used here, the diffusion resistance across the shell is negligibly small.

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Current Progress on Methods and Technologies for Catalytic Methane Activation at Low Temperatures

et al. 2022

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Methane (CH 4 ) is an attractive energy source and important greenhouse gas. Therefore, from the economic and environmental point of view, scientists are working hard to activate and convert CH 4 into various products or less harmful gas at low-temperature. Although the inert nature of C-H bonds requires high dissociation energy at high temperatures, the efforts of researchers have demonstrated the feasibility of catalysts to activate CH 4 at low temperatures. In this review, the efficient catalysts designed to reduce the CH 4 oxidation temperature and improve conversion efficiencies are described. First, noble metals and transition metal-based catalysts are summarized for activating CH 4 in temperatures ranging from 50 to 500 °C. After that, the partial oxidation of CH 4 at relatively low temperatures, including thermocatalysis in the liquid phase, photocatalysis, electrocatalysis, and nonthermal plasma technologies, is briefly discussed. Finally, the challenges and perspectives are presented to provide a systematic guideline for designing and synthesizing the highly efficient catalysts in the complete/partial oxidation of CH 4 at low temperatures.

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Stability of Pd-Pt catalysts in low-temperature wet methane combustion: Metal ratio and particle reconstruction

Cited by 29 publications

References 72 publications

CH₄ Oxidation Activity in Pd and Pt–Pd Bimetallic Catalysts: Correlation with Surface PdO_x Quantified from the DRIFTS Study

CH₄ Oxidation Activity in Pd and Pt–Pd Bimetallic Catalysts: Correlation with Surface PdO_x Quantified from the DRIFTS Study

Kinetics of Low-Temperature Methane Oxidation over SiO₂-Encapsulated Bimetallic Pd–Pt Nanoparticles

Current Progress on Methods and Technologies for Catalytic Methane Activation at Low Temperatures

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Stability of Pd-Pt catalysts in low-temperature wet methane combustion: Metal ratio and particle reconstruction

Cited by 29 publications

References 72 publications

CH4 Oxidation Activity in Pd and Pt–Pd Bimetallic Catalysts: Correlation with Surface PdOx Quantified from the DRIFTS Study

CH4 Oxidation Activity in Pd and Pt–Pd Bimetallic Catalysts: Correlation with Surface PdOx Quantified from the DRIFTS Study

Kinetics of Low-Temperature Methane Oxidation over SiO2-Encapsulated Bimetallic Pd–Pt Nanoparticles

Current Progress on Methods and Technologies for Catalytic Methane Activation at Low Temperatures

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Product

Resources

About

CH₄ Oxidation Activity in Pd and Pt–Pd Bimetallic Catalysts: Correlation with Surface PdO_x Quantified from the DRIFTS Study

CH₄ Oxidation Activity in Pd and Pt–Pd Bimetallic Catalysts: Correlation with Surface PdO_x Quantified from the DRIFTS Study

Kinetics of Low-Temperature Methane Oxidation over SiO₂-Encapsulated Bimetallic Pd–Pt Nanoparticles