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The University of Southampton
Chemistry

Research project: Evans: In situ X-ray absorption spectroscopy for materials and catalyst characterisation

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This form of spectroscopy allows the local structure of a metal centre to be probed in solution or in the solid state, to give estimates of bondlengths, coordination numbers and the types of neighbouring atoms. We are involved with the development of in situ techniques for studying homogeneous and heterogeneous catalysts.

The very intense X-ray sources provided by the Synchrotron Radiation Source (SRS) at the Daresbury Laboratory in Cheshire and the European Synchrotron Radiation Facility (ESRF) in Grenoble are required for this work; from 2007 the new UK synchrotron light source, Diamond, become operational (<>). With these brilliant sources, X-ray spectra can be obtained in sub-second timescales so that reaction intermediates may be studied. An example of this is the stopped-flow energy-dispersive EXAFS technique which we have used to study the formation of homogeneous catalysts. We can also use the high intensity to study very dilute catalysts under operating conditions.

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Rh K-edge XAS of hydroformylation catalysts

Alternatively we can direct the X-ray beam through a small catalytic reactor and investigate the structure and reactivity of catalysts simultaneously, and even incorporate infrared spectroscopy to investigate the adsorbates on metal surfaces during catalysis.

on Beamline ID24 at the ESRF
Diffuse reflectance IR cell

This has shown that metal catalyst change their structure rapidly under reaction conditions. So without this technique, if the structure and the performance of a catalyst are studied under different conditions, any correlation between these disparate measurements may be flawed. Our methods provide detailed understanding of how a catalyst behaves. This is being applied to study key reactions of small molecules, such as the Three Way Automotive Exhaust catalyst, and the Fischer Tropsch reaction for the conversion of synthesis gas (CO/H2) to hydrocarbons and their oxygenates.

Related research groups

Functional Inorganic, Materials and Supramolecular Chemistry
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