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In situ structure-function studies of oxide supported rhodium catalysts by combined energy dispersive XAFS and DRIFTS spectroscopies

In situ structure-function studies of oxide supported rhodium catalysts by combined energy dispersive XAFS and DRIFTS spectroscopies
In situ structure-function studies of oxide supported rhodium catalysts by combined energy dispersive XAFS and DRIFTS spectroscopies
The techniques of energy dispersive EXAFS (EDE), diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) and mass spectrometry (MS) have been combined to study the structure and function of an oxide supported metal catalyst, namely 5 wt% Rh/Al2O3. Using a FreLoN camera as the EDE detector and a rapid-scanning IR spectrometer, experiments could be performed with a repetition rate of 50 ms. The results show that the nature of the rhodium centers is a function of the partial pressures of the reacting gases (CO and NO) and also temperature. This combination of gases oxidizes metallic rhodium particles to Rh(CO)2 at room temperature. The proportion of the rhodium adopting this site increases as the temperature is raised (up to 450 K). Above that temperature the dicarbonyl decomposes and the metal reclusters. Once this condition is met, catalysis ensues. Gas switching techniques show that at 573 K with NO in excess, the clusters can be oxidized rapidly to afford a linear nitrosyl complex; re-exposure to CO also promotes reclustering and the CO adopts terminal (atop) and bridging (2-fold) sites.
xafs, catalysis, ir, rhodium
1551-7616
603-607
Evans, John
05890433-0155-49fe-a65d-38c90ea25c69
Dent, Andrew J.
24c2a218-cb0e-4193-af0b-3ff1dc42b552
Diaz-Moreno, Sofia
4e280df3-7f62-4280-8058-2803c740ae00
Fiddy, Steven G.
f6c255cf-6aa1-4798-85ca-1a2ccdaa1186
Jyoti, Bhrat
9e00e347-0864-48fa-9bb8-f44f98161fd0
Newton, Mark A.
73aab2af-4641-47f3-89ad-3b7d3026164f
Tromp, Moniek
48c1ebbb-579c-42b6-83bb-7188c668b322
Evans, John
05890433-0155-49fe-a65d-38c90ea25c69
Dent, Andrew J.
24c2a218-cb0e-4193-af0b-3ff1dc42b552
Diaz-Moreno, Sofia
4e280df3-7f62-4280-8058-2803c740ae00
Fiddy, Steven G.
f6c255cf-6aa1-4798-85ca-1a2ccdaa1186
Jyoti, Bhrat
9e00e347-0864-48fa-9bb8-f44f98161fd0
Newton, Mark A.
73aab2af-4641-47f3-89ad-3b7d3026164f
Tromp, Moniek
48c1ebbb-579c-42b6-83bb-7188c668b322

Evans, John, Dent, Andrew J., Diaz-Moreno, Sofia, Fiddy, Steven G., Jyoti, Bhrat, Newton, Mark A. and Tromp, Moniek (2007) In situ structure-function studies of oxide supported rhodium catalysts by combined energy dispersive XAFS and DRIFTS spectroscopies. AIP Conference Proceedings, 882, 603-607. (doi:10.1063/1.2644606).

Record type: Article

Abstract

The techniques of energy dispersive EXAFS (EDE), diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) and mass spectrometry (MS) have been combined to study the structure and function of an oxide supported metal catalyst, namely 5 wt% Rh/Al2O3. Using a FreLoN camera as the EDE detector and a rapid-scanning IR spectrometer, experiments could be performed with a repetition rate of 50 ms. The results show that the nature of the rhodium centers is a function of the partial pressures of the reacting gases (CO and NO) and also temperature. This combination of gases oxidizes metallic rhodium particles to Rh(CO)2 at room temperature. The proportion of the rhodium adopting this site increases as the temperature is raised (up to 450 K). Above that temperature the dicarbonyl decomposes and the metal reclusters. Once this condition is met, catalysis ensues. Gas switching techniques show that at 573 K with NO in excess, the clusters can be oxidized rapidly to afford a linear nitrosyl complex; re-exposure to CO also promotes reclustering and the CO adopts terminal (atop) and bridging (2-fold) sites.

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Published date: 2 February 2007
Additional Information: X-Ray Absorption Fine Structure - XAFS13: 13th International Conference
Keywords: xafs, catalysis, ir, rhodium

Identifiers

Local EPrints ID: 47101
URI: http://eprints.soton.ac.uk/id/eprint/47101
ISSN: 1551-7616
PURE UUID: b0fbc153-c85a-4883-8dc5-9cb938785c3e
ORCID for John Evans: ORCID iD orcid.org/0000-0003-3290-7785

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Date deposited: 26 Jul 2007
Last modified: 29 Oct 2024 02:32

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Contributors

Author: John Evans ORCID iD
Author: Andrew J. Dent
Author: Sofia Diaz-Moreno
Author: Steven G. Fiddy
Author: Bhrat Jyoti
Author: Mark A. Newton
Author: Moniek Tromp

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