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Hydrogen effect on the preferential oxidation of carbon monoxide over alumina-supported gold nanoparticles

Paper ID Volume ID Publish Year Pages File Format Full-Text
48234 46497 2008 7 PDF Available
Title
Hydrogen effect on the preferential oxidation of carbon monoxide over alumina-supported gold nanoparticles
Abstract

Although alumina-supported gold nanoparticles are poor catalysts for the oxidation of carbon monoxide, they have turned out to be promising candidates for the preferential oxidation of CO in hydrogen-rich streams (PrOx), as hydrogen apparently enhances the CO oxidation rate. The mechanism of this promotion effect is unclear. In this study, we carry out kinetic measurements on the PrOx reaction catalyzed by a 0.9% Au/Al2O3 catalyst, which is prepared by direct anionic exchange. We show that the apparent activation energy of the oxidation of CO is lower than that of the oxidation of H2, whatever the hydrogen content in the feed. On the other hand, the hydrogen partial reaction order is higher in the oxidation of H2 than in the oxidation of CO. Thus, the CO oxidation rate is significantly increased at low temperature by the introduction of only a small amount of hydrogen in the reactant mixture. At higher temperatures, the selectivity to CO2 decreases due to competition with the oxidation of H2. Higher hydrogen concentrations cause the competition between CO and H2 oxidations to start at lower temperatures. It is proposed that hydrogen reacts with oxygen to yield highly oxidizing intermediates that selectively react with CO as long as the energetic barrier to produce water from these intermediates is not crossed.

Keywords
Hydrogen; Gold; Alumina; PrOx; CO oxidation; H2 + O2 intermediates
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Hydrogen effect on the preferential oxidation of carbon monoxide over alumina-supported gold nanoparticles
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis B: Environmental - Volume 80, Issues 3–4, 8 May 2008, Pages 195–201
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