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A transient in situ...
A transient in situ FTIR and XANES study of CO oxidation over Pt/Al2O3 catalysts
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- Carlsson, Per-Anders, 1972 (author)
- Chalmers tekniska högskola,Chalmers University of Technology
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- Österlund, Lars, 1967 (author)
- Uppsala universitet,Fasta tillståndets fysik
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- Thormählen, Peter, 1969 (author)
- Chalmers tekniska högskola,Chalmers University of Technology
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- Palmqvist, Anders, 1966 (author)
- Chalmers tekniska högskola,Chalmers University of Technology
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- Fridell, Erik, 1963 (author)
- Chalmers tekniska högskola,Chalmers University of Technology
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- Jansson, Jonas, 1973 (author)
- Chalmers tekniska högskola,Chalmers University of Technology
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- Skoglundh, Magnus, 1965 (author)
- Chalmers tekniska högskola,Chalmers University of Technology
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(creator_code:org_t)
- Elsevier BV, 2004
- 2004
- English.
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In: Journal of Catalysis. - : Elsevier BV. - 0021-9517 .- 1090-2694. ; 226:2, s. 422-434
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Abstract
Subject headings
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- We report experimental results for the oxidation of CO over supported Pt/Al2O3 catalysts operating in oxygen excess at atmospheric pressure. To study the reaction kinetics under transient conditions we have employed step changes of the O2 concentration by intermittently switching off the O2 supply at various temperatures ranging from 523 to 623 K. Detailed in situ FTIR and XANES data for CO coverage and the chemical state of Pt, respectively, are presented together with the CO conversion, which in both cases was monitored by mass spectrometry. A red-shift of the vibrational frequency of linearly bonded CO which correlates with a blue-shift of the Pt LIII binding energy indicates that the Pt catalyst initially is partially oxidised and gradually reduced when the O2 supply is switched off. Control experiments with a NO2 oxidised Pt/Al2O3 catalyst support these findings. A hysteresis in the catalytic activity due to the different rates whereby Pt is oxidised and reduced as a function of gas-phase composition is observed. The activation energy for the Pt oxide reduction (decomposition) process is estimated to be about 50 kJ/mol. The results further emphasise that the conventional three-step Langmuir-Hinshelwood (LH) scheme used to interpret CO oxidation on Pt surfaces must be complemented by a Pt oxidation and reduction mechanism during transient conditions. Moreover, FTIR data suggest that during the extinction, the partially oxidised platinum surface is reduced by chemisorbed CO which should be explicitly accounted for in the modeling of the reaction mechanism.
Subject headings
- NATURVETENSKAP -- Fysik (hsv//swe)
- NATURAL SCIENCES -- Physical Sciences (hsv//eng)
- NATURVETENSKAP -- Geovetenskap och miljövetenskap -- Miljövetenskap (hsv//swe)
- NATURAL SCIENCES -- Earth and Related Environmental Sciences -- Environmental Sciences (hsv//eng)
Keyword
- Ignition
- Platinum
- Step-response experiments
- Pt/Al<sub>2</sub>O<sub>3</sub>
- XANES
- FTIR
- Catalysis
- CO oxidation
- Extinction
- Platinum oxide
Publication and Content Type
- art (subject category)
- ref (subject category)
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Carlsson, Per-An ...
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Österlund, Lars, ...
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Thormählen, Pete ...
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Palmqvist, Ander ...
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Fridell, Erik, 1 ...
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Jansson, Jonas, ...
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Skoglundh, Magnu ...
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- About the subject
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- NATURAL SCIENCES
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NATURAL SCIENCES
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and Physical Science ...
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- NATURAL SCIENCES
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NATURAL SCIENCES
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and Earth and Relate ...
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and Environmental Sc ...
- Articles in the publication
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Journal of Catal ...
- By the university
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Chalmers University of Technology
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Uppsala University