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Rapid monitoring of the nature and interconversion of supported catalyst phases and of their influence upon performance: CO oxidation to CO2 by ?-Al2O3 supported Rh catalysts

Rapid monitoring of the nature and interconversion of supported catalyst phases and of their influence upon performance: CO oxidation to CO2 by ?-Al2O3 supported Rh catalysts
Rapid monitoring of the nature and interconversion of supported catalyst phases and of their influence upon performance: CO oxidation to CO2 by ?-Al2O3 supported Rh catalysts
Spatially and temporally resolved energy dispersive EXAFS (EDE) has been utilised in situ to study supported Rh nanoparticles during CO oxidation by O2 under plug-flow conditions. Three distinct phases of Rh supported upon Al2O3 were identified using EDE at the Rh K edge during CO oxidation. Their presence and interconversion are related to the efficiency of the catalysts in oxidising CO to CO2. A metallic phase is only found at higher temperatures (>450K) and CO fractions (CO/O2 > 1); an oxidic phase resembling Rh2O3 dominates the active catalyst under oxygen-rich conditions. Below ~573K, and in CO rich environments, high proportions of isolated RhI(CO)2 species are found to co-exist with metallic Rh nanoparticles. Alongside these discrete situations a large proportion of the active phase space comprises small Rh cores surrounded by layers of active oxide. Confinement of Rh to nanoscale domains induces structural lability that influences catalytic behaviour. For CO oxidation over Rh/Al2O3 there are two redox phase equilibria alongside the chemistry of CO and O adsorbed upon extended Rh surfaces.
EXAFS spectroscopy, heterogeneous catalysis, microreactors, oxidation, rhodium
0947-6539
1975-1985
Newton, M.A.
cf7f71a3-7c53-46f4-bf2d-9c02e0f2eda0
Dent, A.J.
b5cc5c9e-ae74-45f2-8ac1-685bbcc1f074
Diaz-Moreno, S.
57fde3cb-73fa-48df-b505-79341096a3f1
Fiddy, S.G.
bccae976-2d50-4e80-a0da-705249bc7bc0
Jyoti, B.
5652d1b7-8f16-40f2-b789-c152ed1b1929
Evans, J.
05890433-0155-49fe-a65d-38c90ea25c69
Newton, M.A.
cf7f71a3-7c53-46f4-bf2d-9c02e0f2eda0
Dent, A.J.
b5cc5c9e-ae74-45f2-8ac1-685bbcc1f074
Diaz-Moreno, S.
57fde3cb-73fa-48df-b505-79341096a3f1
Fiddy, S.G.
bccae976-2d50-4e80-a0da-705249bc7bc0
Jyoti, B.
5652d1b7-8f16-40f2-b789-c152ed1b1929
Evans, J.
05890433-0155-49fe-a65d-38c90ea25c69

Newton, M.A., Dent, A.J., Diaz-Moreno, S., Fiddy, S.G., Jyoti, B. and Evans, J. (2006) Rapid monitoring of the nature and interconversion of supported catalyst phases and of their influence upon performance: CO oxidation to CO2 by ?-Al2O3 supported Rh catalysts. Chemistry - A European Journal, 12 (7), 1975-1985. (doi:10.1002/chem.200500644).

Record type: Article

Abstract

Spatially and temporally resolved energy dispersive EXAFS (EDE) has been utilised in situ to study supported Rh nanoparticles during CO oxidation by O2 under plug-flow conditions. Three distinct phases of Rh supported upon Al2O3 were identified using EDE at the Rh K edge during CO oxidation. Their presence and interconversion are related to the efficiency of the catalysts in oxidising CO to CO2. A metallic phase is only found at higher temperatures (>450K) and CO fractions (CO/O2 > 1); an oxidic phase resembling Rh2O3 dominates the active catalyst under oxygen-rich conditions. Below ~573K, and in CO rich environments, high proportions of isolated RhI(CO)2 species are found to co-exist with metallic Rh nanoparticles. Alongside these discrete situations a large proportion of the active phase space comprises small Rh cores surrounded by layers of active oxide. Confinement of Rh to nanoscale domains induces structural lability that influences catalytic behaviour. For CO oxidation over Rh/Al2O3 there are two redox phase equilibria alongside the chemistry of CO and O adsorbed upon extended Rh surfaces.

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More information

Published date: 20 February 2006
Keywords: EXAFS spectroscopy, heterogeneous catalysis, microreactors, oxidation, rhodium

Identifiers

Local EPrints ID: 35502
URI: http://eprints.soton.ac.uk/id/eprint/35502
ISSN: 0947-6539
PURE UUID: 93160ddf-ea9f-413b-a610-1f12b54d9c20

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Date deposited: 17 May 2006
Last modified: 15 Jul 2019 19:05

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