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Title: In Situ Structure-Function Studies of Oxide Supported Rhodium Catalysts by Combined Energy Dispersive XAFS and DRIFTS Spectroscopies

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.

Authors:
 [1];  [2]; ;  [3];  [4]; ;  [1];  [5]
  1. School of Chemistry, University of Southampton, Southampton, SO17 1BJ (United Kingdom)
  2. (United Kingdom)
  3. Diamond Light Source, Chilton, Didcot, OX11 0DE (United Kingdom)
  4. CCLRC Daresbury Laboratory, Warrington, WA4 4AD (United Kingdom)
  5. ESRF, Grenoble, F-38043 (France)
Publication Date:
OSTI Identifier:
21054693
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 882; Journal Issue: 1; Conference: XAFS13: 13. international conference on X-ray absorption fine structure, Stanford, CA (United States), 9-14 Jul 2006; Other Information: DOI: 10.1063/1.2644606; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ABSORPTION SPECTROSCOPY; ALUMINIUM OXIDES; CARBON MONOXIDE; CATALYSIS; CATALYSTS; FINE STRUCTURE; FOURIER TRANSFORM SPECTROMETERS; FOURIER TRANSFORMATION; GASES; INFRARED SPECTRA; INTERFACES; MASS SPECTROSCOPY; NITRIC OXIDE; OXIDATION; PARTIAL PRESSURE; RHODIUM; STRUCTURE FUNCTIONS; X-RAY SPECTROSCOPY

Citation Formats

Evans, John, Diamond Light Source, Chilton, Didcot, OX11 0DE, Dent, Andrew J., Diaz-Moreno, Sofia, Fiddy, Steven G., Jyoti, Bhrat, Tromp, Moniek, and Newton, Mark A. In Situ Structure-Function Studies of Oxide Supported Rhodium Catalysts by Combined Energy Dispersive XAFS and DRIFTS Spectroscopies. United States: N. p., 2007. Web. doi:10.1063/1.2644606.
Evans, John, Diamond Light Source, Chilton, Didcot, OX11 0DE, Dent, Andrew J., Diaz-Moreno, Sofia, Fiddy, Steven G., Jyoti, Bhrat, Tromp, Moniek, & Newton, Mark A. In Situ Structure-Function Studies of Oxide Supported Rhodium Catalysts by Combined Energy Dispersive XAFS and DRIFTS Spectroscopies. United States. doi:10.1063/1.2644606.
Evans, John, Diamond Light Source, Chilton, Didcot, OX11 0DE, Dent, Andrew J., Diaz-Moreno, Sofia, Fiddy, Steven G., Jyoti, Bhrat, Tromp, Moniek, and Newton, Mark A. Fri . "In Situ Structure-Function Studies of Oxide Supported Rhodium Catalysts by Combined Energy Dispersive XAFS and DRIFTS Spectroscopies". United States. doi:10.1063/1.2644606.
@article{osti_21054693,
title = {In Situ Structure-Function Studies of Oxide Supported Rhodium Catalysts by Combined Energy Dispersive XAFS and DRIFTS Spectroscopies},
author = {Evans, John and Diamond Light Source, Chilton, Didcot, OX11 0DE and Dent, Andrew J. and Diaz-Moreno, Sofia and Fiddy, Steven G. and Jyoti, Bhrat and Tromp, Moniek and Newton, Mark A.},
abstractNote = {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.},
doi = {10.1063/1.2644606},
journal = {AIP Conference Proceedings},
number = 1,
volume = 882,
place = {United States},
year = {Fri Feb 02 00:00:00 EST 2007},
month = {Fri Feb 02 00:00:00 EST 2007}
}