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XANES and EXAFS studies on metal nanoparticle growth and bimetallic interaction of Ni-based catalysts for CO2 reforming of CH4

Paper ID Volume ID Publish Year Pages File Format Full-Text
54854 47029 2013 10 PDF Available
Title
XANES and EXAFS studies on metal nanoparticle growth and bimetallic interaction of Ni-based catalysts for CO2 reforming of CH4
Abstract

Two groups of catalysts containing Ni and/or Co metals and MgAlOx as support material were made using coprecipitation and incipient wetness impregnation methods, respectively. The mechanism of metal particle growth during reduction of the monometallic Ni or Co and bimetallic Ni–Co catalysts was studied using X-ray absorption near edge spectroscopy (XANES) and extended X-ray absorption fine structure spectroscopy (EXAFS). The results show that the bimetallic Ni–Co catalysts made by coprecipitation method resulted in smaller metal nanoparticles upon reduction. TEM confirmed this observation and revealed that this catalyst has well-dispersed, more uniform metal particles. The metal reduction extent of Ni monometallic catalysts and the bimetallic catalysts made by impregnation was similar with respect to each metal. For the bimetallic Ni–Co catalysts made by coprecipitation, the interactions between two metals in reduction were observed such that Ni reduction was mitigated by Co, and Co reduction was promoted by Ni. And the first derivative of XANES of such made catalysts indicated stronger interaction between Ni and Co atoms and, perhaps, alloy formation. Time resolved analysis found that Ni reduction followed the second order kinetics at early stage and Co proceeded through the zero order all the way in catalyst reduction. The catalyst stability enhancement by Co atoms and the mechanism of Ni and Co interaction during reduction are explained.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (349 K)Download as PowerPoint slideHighlights► XANES and EXAFS show the differences in Ni and Co reduction in catalysts made by coprecipitation and impregnation. ► The stronger interaction between Ni and Co in catalysts made by coprecipitation results in small and well-dispersed metal nanoparticles. ► Co in bimetallic Ni–Co catalysts stabilizes the solid structures and lessens Ni reduction; while Ni enhances Co reduction. ► The energy shift in pre-edge 1s to 3d transition peak may indicate Ni–Co alloy formation in the bimetallic catalysts made by coprecipitation. ► Nickel reduction rate follows the second-order and that of cobalt proceeds through the zero-order with respect to corresponding oxides.

Keywords
Metal nanoparticles; Catalyst reduction; XANES; EXFAS; CO2 reforming of CH4
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XANES and EXAFS studies on metal nanoparticle growth and bimetallic interaction of Ni-based catalysts for CO2 reforming of CH4
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Publisher
Database: Elsevier - ScienceDirect
Journal: Catalysis Today - Volume 207, 30 May 2013, Pages 3–12
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