Supported Vanadium Oxide Catalysts as an Illustrative Example

Resonance Raman Spectroscopy - 0-Al2O3-Supported Vanadium Oxide Catalysts as an Illustrative Example 

Meted Oxide Catedysis. Edited by S. David Jackson and Justin S. J. Hargreaves Copyright 2009 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim ISBN 978-3-527-31815-5 

In addition to the structure in the dehydrated state, the structure of supported vanadia catalysts under redox reaction conditions is directly related to the catalytic performance. Vanadia catalysts are usually reduced to some extent during a redox reaction, and the reduced vanadia species have been proposed as the active sites [4, 19-24]. Therefore, information on the valence state and molecular structure of the reduced vanadia catalysts is of great interest. A number of techniques have been applied to investigate the reduction of supported vanadia catalysts, such as temperature programmed reduction (TPR) [25-27], X-ray photoelectron spectroscopy (XPS) [21], electron spin resonance (ESR) [22], UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS) [18, 28-32], X-ray absorption fine structure spectroscopy (XAFS) [11] and Raman spectroscopy [5, 26, 33-41]. Most of these techniques give information only on the oxidation state of vanadium species. Although Raman spectroscopy is a powerful tool for characterization of the molecular structure of supported vanadia [4, 29, 42], it has been very difficult to detect reduced supported 

In this case study, we have carried out further investigation into the structure of VO, supported on alumina under both oxidized (dehydrated) and reduced environments using both UV- (244 nm) and visible- (488 nm) excited Raman spectroscopy. Special attention has been directed towards the structure of supported VO at extremely low surface density (down to 0.01 Vnm ). 

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