Molecular mechanism of propane oxidative dehydrogenation on surface oxygen radical sites of VO x /TiO2 catalysts

Molecular mechanism of propane oxidative dehydrogenation on surface oxygen radical sites of VO x... Minimum energy pathways of propane oxidative dehydrogenation to propene and propanol on supported vanadium oxide catalyst VO x /TiO2 were studied by periodic discrete Fourier transform (DFT) using a surface oxygen radical as the active site. The propene formation pathway was shown to consist of two consecutive hydrogen abstraction steps. The first step includes Cβ–H bond activation of propane followed by the formation of a surface hydroxyl group V–O t H and a propyl radical n-C3H7. This step with the activation energy E* = 0.56 eV (54.1 kJ/mol) appears to be rate-determining. The second step involves the reaction of the bridging O b oxygen atom with the methylene C–H bond of propyl radical n-C3H7 followed by the formation of a hydroxylated surface site HO t –V4+–O b H and propene. The initial steps of the C–H bond activation during propane conversion to propanol and propene by ODH on V5+–(O t O b )− active sites are identical. The obtained results demonstrate that participation of surface oxygen radicals as the active sites of propane ODH makes it possible to explain relatively low activation energies observed for this reaction on the most active catalysts. The presence of very active radical species in low concentration seems to be the key factor for obtaining high selectivity. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Research on Chemical Intermediates Springer Journals

Molecular mechanism of propane oxidative dehydrogenation on surface oxygen radical sites of VO x /TiO2 catalysts

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Publisher
Springer Netherlands
Copyright
Copyright © 2015 by Springer Science+Business Media Dordrecht
Subject
Chemistry; Catalysis; Physical Chemistry; Inorganic Chemistry
ISSN
0922-6168
eISSN
1568-5675
D.O.I.
10.1007/s11164-015-2355-0
Publisher site
See Article on Publisher Site

Abstract

Minimum energy pathways of propane oxidative dehydrogenation to propene and propanol on supported vanadium oxide catalyst VO x /TiO2 were studied by periodic discrete Fourier transform (DFT) using a surface oxygen radical as the active site. The propene formation pathway was shown to consist of two consecutive hydrogen abstraction steps. The first step includes Cβ–H bond activation of propane followed by the formation of a surface hydroxyl group V–O t H and a propyl radical n-C3H7. This step with the activation energy E* = 0.56 eV (54.1 kJ/mol) appears to be rate-determining. The second step involves the reaction of the bridging O b oxygen atom with the methylene C–H bond of propyl radical n-C3H7 followed by the formation of a hydroxylated surface site HO t –V4+–O b H and propene. The initial steps of the C–H bond activation during propane conversion to propanol and propene by ODH on V5+–(O t O b )− active sites are identical. The obtained results demonstrate that participation of surface oxygen radicals as the active sites of propane ODH makes it possible to explain relatively low activation energies observed for this reaction on the most active catalysts. The presence of very active radical species in low concentration seems to be the key factor for obtaining high selectivity.

Journal

Research on Chemical IntermediatesSpringer Journals

Published: Nov 25, 2015

References

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