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Elucidation of structure–activity relationships of model three way catalysts for the combustion of methane

Paper ID Volume ID Publish Year Pages File Format Full-Text
47419 46471 2010 8 PDF Available
Title
Elucidation of structure–activity relationships of model three way catalysts for the combustion of methane
Abstract

The combustion of methane on model three way catalysts (TWC) Pd/CeZrO2 and Pd/LaFeO3 (2 wt.% Pd) was studied under lean conditions in the temperature range between ca. 200 and 800 °C to investigate the catalytic performance at and after high temperatures. The catalysts were prepared by incipient wetness impregnation and the nature and distribution of palladium species was characterized by N2-physisorption, X-ray diffraction (XRD), visible Raman spectroscopy, X-ray absorption spectroscopy (XANES and EXAFS), H2-temperature programmed reduction (H2-TPR), CO adsorption followed by diffuse reflectance infrared Fourier transform spectroscopy (CO-DRIFTS) and CO chemisorption. The behaviour of Pd during the combustion was monitored by in situ XANES spectroscopy. The characterization results indicate that the dispersion of Pd is higher in Pd/CeZrO2 than in Pd/LaFeO3. The catalytic data reveal that Pd/CeZrO2 is more active and stable compared to Pd/LaFeO3 in the whole studied temperature range. This is also true even after subjecting the catalysts to reaction at ≥800 °C as evidenced by the extent of hysteresis observed in the conversion profiles. In situ XANES studies indicate that palladium had been in the oxidized state when the catalysts showed the best combustion performance. The studies also indicate that a fraction of PdOx had been reduced when the hysteresis was observed in the conversion profiles (while cooling between ca. 680 and 560 °C) implying that the PdOx species are the active sites, at least at T ≤ 700 °C.

Keywords
Methane combustion; Model three way catalysts; Pd/CeZrO2; Pd/LaFeO3; In situ XANES; Active sites
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Elucidation of structure–activity relationships of model three way catalysts for the combustion of methane
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis B: Environmental - Volume 94, Issues 1–2, 1 February 2010, Pages 77–84
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
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Any Questions? feel free to contact us