Catalyst microstructure and methane oxidation reactivity during the Pd↔PdO transformation on alumina supports

Datye, Abhaya K.; Bravo, Jaime; Nelson, Travis; Atanasova, P.; Lyubovsky, Maxim; Pfefferle, Lisa D.

doi:10.1016/s0926-860x(99)00512-8

Cited by 325 publications

(199 citation statements)

References 21 publications

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“…[7] Comparatively little studies on the interaction of Pd with oxygen have been conducted by electron microscopy techniques. Lyubovsky et al [24] and Datye et al [11] reported on microstructural modifications of impregnated Pd-Al 2 O 3 catalysts during the transformation from Pd to PdO and established a correlation to the reactivity in methane oxidation. Electron microscopy was also used to characterize the state of Pd during other hydrocarbon oxidation reactions.…”

Section: Introductionmentioning

confidence: 99%

“…[1,2,3,4,5,6,7,8] Hence, there is a growing need to understand the key parameters determining the reaction mechanisms. One of the most important parameters crucially influencing the catalytic activity of Pd-based catalysts is their chemical state under reaction conditions which is known to switch between metallic and oxidic under typical reaction conditions, [6,9,10,11] depending on O 2 pressure and temperature.…”

Section: Introductionmentioning

confidence: 99%

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Growth and decomposition of aligned and ordered PdO nanoparticles

Penner

Wang

Jenewein

et al. 2006

The Journal of Chemical Physics

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The formation, thermal decomposition, and reduction of small PdO particles were studied by high-resolution transmission electron microscopy and selected area electron diffraction. Welldefined Pd particles (mean size of 5-7 nm) were grown epitaxially on NaCl (001) surfaces and subsequently covered by a layer of amorphous SiO 2 (25 nm), prepared by reactive deposition of SiO in 10 -2 Pa O 2 . The resulting films were exposed to molecular O 2 in the temperature range of 373-673 K, and the growth of PdO was studied. The formation of a PdO phase starts at 623 K and is almost completed at 673 K. The high-resolution experiments suggest a topotactic growth of PdO crystallites on top of the original Pd particles. Subsequent reaction of the PdO in 10 mbar CO for 15 min and thermal decomposition in 1 bar He for 1 h were also investigated in the temperature range from 373 to 573 K. Reductive treatments in CO up to 493 K do not cause a significant change in the PdO structure. The reduction of PdO starts at 503 K and is completed at 523 K. In contrast, PdO decomposes in 1 bar He at around 573 K. The mechanism of PdO growth and decay is discussed and compared to results of previous studies on other metals, e.g., on rhodium.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Growth and decomposition of aligned and ordered PdO nanoparticles

Penner

Wang

Jenewein

et al. 2006

The Journal of Chemical Physics

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“…Subsequent cooling in air below 650 °C causes some re-dispersion with the formation of a surface rich in PdOx (PdOx-Pd/Al2O3). The re-dispersion model was confirmed by Datye, et al [13], who further demonstrated that PdO decomposition at higher temperatures (>800 °C) leads to re-dispersion being more difficult. The hysteresis (temperature difference) for decomposition and reformation is also strongly dependent on the nature of the support material [14,15], in the following decreasing order: ZrO2 > Al2O3 > Ta2O3 > TiO2 > CeO2.…”

Section: Aging-induced Pd Sintering: the Primary Catalyst Deactivatiomentioning

confidence: 64%

Part II: Oxidative Thermal Aging of Pd/Al2O3 and Pd/CexOy-ZrO2 in Automotive Three Way Catalysts: The Effects of Fuel Shutoff and Attempted Fuel Rich Regeneration

2015

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Abstract:The Pd component in the automotive three way catalyst (TWC) experiences deactivation during fuel shutoff, a process employed by automobile companies for enhancing fuel economy when the vehicle is coasting downhill. The process exposes the TWC to a severe oxidative aging environment with the flow of hot (800 °C-1050 °C) air. Simulated fuel shutoff aging at 1050 °C leads to Pd metal sintering, the main cause of irreversible deactivation of 3% Pd/Al2O3 and 3% Pd/CexOy-ZrO2 (CZO) as model catalysts. The effect on the Rh component was presented in our companion paper Part I. Moderate support sintering and Pd-CexOy interactions were also experienced upon aging, but had a minimal effect on the catalyst activity losses. Cooling in air, following aging, was not able to reverse the metallic Pd sintering by re-dispersing to PdO. Unlike the aged Rh-TWCs (Part I), reduction via in situ steam reforming (SR) of exhaust HCs was not effective in reversing the deactivation of aged Pd/Al2O3, but did show a slight recovery of the Pd activity when CZO was the carrier. The Pd couples in Pd/CZO are reported to promote the catalytic SR by improving the redox efficiency during the regeneration, while no such promoting effect was observed for Pd/Al2O3. A suggestion is made for improving the catalyst performance. OPEN ACCESSCatalysts 2015, 5 1798 Keywords: automotive three way catalysts (TWC); Pd/Al2O3; Pd/CexOy-ZrO2; fuel shutoff aging; catalyst deactivation; fuel rich regeneration; metal sintering; metal-support interaction

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“…The binding energy of Pd 3d 5/2 observed is higher than that of Pd metal (334.6 eV 79 , 335.1 eV [80][81][82] ). Referring to an earlier report 57 , the spectrum of Pd 3d 5/2 can be deconvoluted into 3 peaks with peak positions corresponding to Pd-N (338.7 eV) 83 , Pd-Cl (337.8 eV) [84][85][86] and Pd-O (336.9 eV) 87 to be Pd-N : Pd-Cl : Pd-O = 0.01 : 0.11 : 0.88 54 (peak ratio). Pd on the APTS-SAM was mainly combined with O as Pd-O (336.9 eV).…”

Section: Electrical Property Of In 2 O 3 Thin Filmsmentioning

confidence: 99%

Nanofabrication of Metal Oxide Patterns Using Self-Assembled Monolayers

Masuda¹

2011

Nanofabrication

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Catalyst microstructure and methane oxidation reactivity during the Pd↔PdO transformation on alumina supports

Cited by 325 publications

References 21 publications

Growth and decomposition of aligned and ordered PdO nanoparticles

Growth and decomposition of aligned and ordered PdO nanoparticles

Part II: Oxidative Thermal Aging of Pd/Al2O3 and Pd/CexOy-ZrO2 in Automotive Three Way Catalysts: The Effects of Fuel Shutoff and Attempted Fuel Rich Regeneration

Nanofabrication of Metal Oxide Patterns Using Self-Assembled Monolayers

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