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A study on the catalytic synergy effect between noble metals and cobalt phases in Ce-Al-O supported catalysts

Paper ID Volume ID Publish Year Pages File Format Full-Text
44618 46046 2006 7 PDF Available
Title
A study on the catalytic synergy effect between noble metals and cobalt phases in Ce-Al-O supported catalysts
Abstract

A series of Co-Pt(Pd, Rh)/Ce-Al-O catalysts were prepared by successive wetness impregnation method. The catalytic activities of the samples for CO oxidation were evaluated in a flow fixed-bed micro-reactor. The techniques of XRD, XPS, EXAFS, H2-TPR and TPO-MS were employed to characterize the catalysts. The results of activity measurement show that for CO oxidation the presence of a small amount of noble metals greatly enhances the activity of Co/Ce-Al-O catalyst, the existence of cerium has increased the activity of the samples because of its capacity for oxygen storage and the interaction between cerium oxide and cobalt phase. The structural characterization results of XRD, XPS and EXAFS indicate that the cobalt in Co-Pt(Pd, Rh)/Ce-Al-O catalysts exists as metallic phase, while in Co/Ce-Al-O catalyst only part of the cobalt has been reduced to zero valence, the rest exists as Co-Al spinel which cannot be reduced at 450 °C by H2. H2-TPR results suggest that the hydrogen spillover may occur during the reduction pretreatment, and therefore increasing the reduction deepness of cobalt phases. The results of TPO-MS show that the oxygen spillover from noble metals to cobalt phase during CO oxidation is very potential. It decreases the activation energy of CO oxidation reaction and results in a prominent increase of the activity. The spilled over species, such as atomic H and O, generated on noble metal sites are mobile on the surface of the catalysts, which makes both of the close and remote cobalt phases involve in reactions at lower temperatures. Additionally, the coordination numbers from EXAFS indicate that the presence of noble metals greatly enhances the dispersion of cobalt phases. The order of this enhancement effect is Pt > Pd > Rh. As a result, the oxygen spillover effect and the enhancement effects on the reduction deepness and the dispersion of cobalt phases should be the main contributions to the catalytic synergy effect between cobalt phases and noble metals.

Keywords
Co-Pt(Pd, Rh)/Ce-Al-O catalysts; CO oxidation; Hydrogen spillover; Oxygen spillover; Catalytic synergy effect; Structural characterization
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A study on the catalytic synergy effect between noble metals and cobalt phases in Ce-Al-O supported catalysts
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 301, Issue 2, 24 February 2006, Pages 145–151
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