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  Not only V(V) - What really is the nature of supported vanadate catalysts?

Klose, F., Wolff, T., Lorenz, H., Seidel-Morgenstern, A., Suchorski, Y., Piorkowska, M., et al. (2007). Not only V(V) - What really is the nature of supported vanadate catalysts?. Poster presented at EUROPACAT-VIII, Turku / Åbo, Finland.

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Item Permalink: http://hdl.handle.net/11858/00-001M-0000-0014-7112-3 Version Permalink: http://hdl.handle.net/11858/00-001M-0000-0025-727F-1
Genre: Poster

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 Creators:
Klose, Frank1, Author              
Wolff, Tanya2, Author              
Lorenz, Heike2, Author              
Seidel-Morgenstern, Andreas1, 2, Author              
Suchorski, Y., Author
Piorkowska, M.1, Author
Weiss, H.1, Author
Affiliations:
1Otto-von-Guericke-Universität Magdeburg, External Organizations, ou_1738156              
2Physical and Chemical Foundations of Process Engineering, Max Planck Institute for Dynamics of Complex Technical Systems, Max Planck Society, ou_1738150              

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Free keywords: Supported vanadia catalysts, Reducibility, Vanadia phases; Ethane oxidation; Selective oxidation, Structure-activity relations
 Abstract: In supported vanadate catalysts the V atoms are commonly assumed to be mostly in oxidation state +5 in the oxidized state. However, H/V ratios of less than 2 are often observed in TPR experiments, and significant fractions of V(IV) species are observed using the XPS, UV-VIS or ESR techniques. The aim of this contribution is to clarify this discrepancy. From the TPR, XPS, BET, XRD, TEM, DRIFTS and pyridine TPD data as well as from a structure-activity analysis in ethane oxidation, it can be concluded that in isolated and polymerized vanadates only 1/3 of V (but 80 % of V in crystalline V2O5 phases) can reach the oxidation state +5. The other V centers remain at oxidation state +4 even after oxidizing or various redox treatments. This implies the existence of two different kinds of V species within the vanadate structures. However, M-O-V(V) bonds as active sites and V=O bonds should be present to reach consistence with spectroscopic data and to explain the support effects. The smallest unit which meets these requirements is [V3O8]3- (3 support bonds) for the isolated vanadates. For polyvanadates a structure with the sequence (-V(IV)-O-V(V)-O-V(IV)-O-)n is postulated.

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Language(s): eng - English
 Dates: 2007
 Publication Status: Not specified
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: -
 Degree: -

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Title: EUROPACAT-VIII
Place of Event: Turku / Åbo, Finland
Start-/End Date: 2007-08-26 - 2007-08-31

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