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Characterization and oxidation states of Cu and Pd in Pd–CuO/ZnO/ZrO2 catalysts for hydrogen production by methanol partial oxidation

Paper ID Volume ID Publish Year Pages File Format Full-Text
43162 45957 2009 12 PDF Available
Title
Characterization and oxidation states of Cu and Pd in Pd–CuO/ZnO/ZrO2 catalysts for hydrogen production by methanol partial oxidation
Abstract

Copper and zinc oxide based catalysts prepared by coprecipitation were promoted with palladium and ZrO2, and their activity and selectivity for methanol oxidative reforming was measured and characterized by N2O decomposition, X-ray absorption spectroscopy, BET, X-ray photoelectron spectroscopy, X-ray diffraction, and temperature programmed reduction. Addition of ZrO2 increased copper dispersion and surface area, with little effect on activity, while palladium promotion significantly enhanced activity with little change of the catalytic structure. A catalyst promoted with both ZrO2 and palladium yielded hydrogen below 150 °C. EXAFS results under reaction conditions showed that the oxidation state of copper was influenced by palladium in the catalyst bulk. A palladium promoted catalyst contained 90% Cu0, while the copper in an unpromoted catalyst was 100% Cu1+ at the same temperature. Palladium preferentially forms an unstable alloy with copper instead of zinc during reduction, which persists during reaction regardless of copper oxidation state. A 100-h time on stream activity measurement showed growth in copper crystallites and change in copper oxidation state resulting in decreasing activity and selectivity. A kinetic model of the reaction pathway showed that palladium and ZrO2 promoters lower the activation energy of methanol combustion and steam reforming reactions.

Graphical abstractCopper and zinc based catalysts were promoted with palladium and zirconium. The zirconium promoter increased copper dispersion, while the palladium promoter enhanced copper reducibility under reaction conditions. Upon reduction, palladium was found to form alloys with copper, which was reversible on exposure to air. Deactivated catalyst had a greater fraction of copper as Cu1+ under reaction conditions.Figure optionsDownload full-size imageDownload as PowerPoint slide

Keywords
Methanol; Partial oxidation; Copper; Palladium alloy; X-ray absorption spectroscopy
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Characterization and oxidation states of Cu and Pd in Pd–CuO/ZnO/ZrO2 catalysts for hydrogen production by methanol partial oxidation
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 352, Issues 1–2, 15 January 2009, Pages 133–144
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
Online Support
Any Questions? feel free to contact us