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New approaches to preferential CO oxidation over noble metals

Paper ID Volume ID Publish Year Pages File Format Full-Text
47264 46465 2010 11 PDF Available
Title
New approaches to preferential CO oxidation over noble metals
Abstract

Features of preferential CO oxidation (CO-PROX) over alumina-supported Pt-, Rh-, Ru-, Au-catalysts are investigated. As found in experiments (flow reactor of quartz, hydrogen-containing gas with admixtures of CO, O2 ∼ 1 vol.%, high gas flow rate), the nature of CO-PROX is found to be governed by a combination of two main decisive factors: high exothermicity of reactions (CO, H2 oxidation), and peculiarities of interaction of reaction mixture components with metal. Due to high exothermicity, CO-PROX can be realized in a special macrokinetic mode, catalyst surface ignition (CSI), which is an external mass transfer control regime on O2 as the key component.The reaction can be transferred into CSI mode either by heating up to the critical temperature of ignition or by feeding the reaction gas to the catalyst at temperatures above the critical value. In heating, the transition into CSI mode starts with an overheat of the catalyst downstream, after which “hot spot” of the reaction drifts upstream. Variations of temperature allow to observe both ignition and extinction of catalyst surface.Experiments performed with gas mixtures of different composition showed that in CO absence from the reaction gas, H2 is easily oxidized over Pt and Rh at rather low temperatures close to a room one; reaction proceeds in CSI mode with the “hot spot” at the top of the catalyst bed. In CO-PROX over Pt, Rh, there is a deactivating effect of strong CO adsorption, while for Ru it is strong O2 adsorption. As in the case of Ru-catalysts, hydrogen makes substantial positive effect on CO oxidation over Au-catalysts.Effects of temperature, O2 content in gas, Rh content in catalysts are investigated. It is found that a decrease in residual CO content in CSI mode is favored by higher O2 content, lower temperature and lower metal content (for example, down from 1 to 0.2 wt.%).

Keywords
Preferential CO oxidation; Surface ignition; Platinum-group metals; Gold; Strong adsorption
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis B: Environmental - Volume 98, Issues 3–4, 1 August 2010, Pages 193–203
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
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