Structural characterization of alumina-supported Rh catalysts: effects of ceriation and zirconiation by using metal–organic precursors
Structural characterization of alumina-supported Rh catalysts: effects of ceriation and zirconiation by using metal–organic precursors
The effects of the addition of ceria and zirconia on the structural properties of supported rhodium catalysts (1.6 and 4 wt?% Rh/?-Al2O3) are studied. Ceria and zirconia are deposited by using two preparation methods. Method I involves the deposition of ceria on ?-Al2O3 from Ce(acac)3, and the rhodium metal is subsequently added, whereas method II is based on a controlled surface reaction technique, that is, the decomposition of metal–organic M(acac)x (in which M=Ce, x=3 and M=Zr, x=4) on Rh/?-Al2O3. The structures of the prepared catalyst materials are characterized ex situ by using N2 physisorption, transmission electron microscopy, high-angle annular dark-field scanning transmission election microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray absorption fine structure spectroscopy (XAFS). All supported rhodium systems readily oxidize in air at room temperature. By using ceriated and zirconiated precursors, a larger rhodium-based metallic core fraction is obtained in comparison to the undoped rhodium catalysts, suggesting that ceria and zirconia protect the rhodium particles against extensive oxidation. XPS results indicate that after the calcination and reduction treatments, a small amount of chlorine is retained on the support of all rhodium catalysts. EXAFS analysis shows significant RhCl interactions for Rh/Al2O3 and Rh/CeOx/Al2O3 (method I) catalysts. After reaction with H2/He in situ, for series of samples with 1.6 wt?% Rh, the EXAFS first shell analysis affords a mean size of approximately 30 atoms. A broader spread is evident with a 4 wt?% rhodium loading (ca. 30–110 atoms), with the incorporation of zirconium providing the largest particle sizes.
cerium, EXAFS spectroscopy, photoelectron spectroscopy, rhodium, zirconium
3606-3617
Kroner, Anna B.
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Newton, Mark A.
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Tromp, Moniek
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Russell, Andrea E.
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Dent, Andrew J.
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Evans, John
05890433-0155-49fe-a65d-38c90ea25c69
13 August 2013
Kroner, Anna B.
e0f05400-c002-4d09-83c0-70d91edb52c2
Newton, Mark A.
73aab2af-4641-47f3-89ad-3b7d3026164f
Tromp, Moniek
48c1ebbb-579c-42b6-83bb-7188c668b322
Russell, Andrea E.
b6b7c748-efc1-4d5d-8a7a-8e4b69396169
Dent, Andrew J.
24c2a218-cb0e-4193-af0b-3ff1dc42b552
Evans, John
05890433-0155-49fe-a65d-38c90ea25c69
Kroner, Anna B., Newton, Mark A., Tromp, Moniek, Russell, Andrea E., Dent, Andrew J. and Evans, John
(2013)
Structural characterization of alumina-supported Rh catalysts: effects of ceriation and zirconiation by using metal–organic precursors.
ChemPhysChem, 14 (15), .
(doi:10.1002/cphc.201300537).
Abstract
The effects of the addition of ceria and zirconia on the structural properties of supported rhodium catalysts (1.6 and 4 wt?% Rh/?-Al2O3) are studied. Ceria and zirconia are deposited by using two preparation methods. Method I involves the deposition of ceria on ?-Al2O3 from Ce(acac)3, and the rhodium metal is subsequently added, whereas method II is based on a controlled surface reaction technique, that is, the decomposition of metal–organic M(acac)x (in which M=Ce, x=3 and M=Zr, x=4) on Rh/?-Al2O3. The structures of the prepared catalyst materials are characterized ex situ by using N2 physisorption, transmission electron microscopy, high-angle annular dark-field scanning transmission election microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray absorption fine structure spectroscopy (XAFS). All supported rhodium systems readily oxidize in air at room temperature. By using ceriated and zirconiated precursors, a larger rhodium-based metallic core fraction is obtained in comparison to the undoped rhodium catalysts, suggesting that ceria and zirconia protect the rhodium particles against extensive oxidation. XPS results indicate that after the calcination and reduction treatments, a small amount of chlorine is retained on the support of all rhodium catalysts. EXAFS analysis shows significant RhCl interactions for Rh/Al2O3 and Rh/CeOx/Al2O3 (method I) catalysts. After reaction with H2/He in situ, for series of samples with 1.6 wt?% Rh, the EXAFS first shell analysis affords a mean size of approximately 30 atoms. A broader spread is evident with a 4 wt?% rhodium loading (ca. 30–110 atoms), with the incorporation of zirconium providing the largest particle sizes.
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Submitted date: 7 June 2013
Published date: 13 August 2013
Keywords:
cerium, EXAFS spectroscopy, photoelectron spectroscopy, rhodium, zirconium
Organisations:
Organic Chemistry: Synthesis, Catalysis and Flow, Electrochemistry
Identifiers
Local EPrints ID: 362452
URI: http://eprints.soton.ac.uk/id/eprint/362452
ISSN: 1439-4235
PURE UUID: cb3d765a-0300-4449-8199-cec9d21e4047
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Date deposited: 25 Feb 2014 10:14
Last modified: 29 Oct 2024 02:32
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Contributors
Author:
Anna B. Kroner
Author:
Mark A. Newton
Author:
Moniek Tromp
Author:
Andrew J. Dent
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