A density functional theory study of the oxidation of methanol to formaldehyde over vanadia supported on silica, titania, and zirconia

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Density functional theory was used to investigate the mechanism and kinetics of methanol oxidation to formaldehyde over vanadia supported on silica, titania, and zirconia. The catalytically active site was modeled as an isolated VO{sub 4} unit attached to the support. The calculated geometry and vibrational frequencies of the active site are in good agreement with experimental measurements both for model compounds and oxide-supported vanadia. Methanol adsorption is found to occur preferentially with the rupture of a V-O-M bond (M = Si, Ti, Zr) and with preferential attachment of a methoxy group to V. The vibrational frequencies of the methoxy group ... continued below

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29 pages

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Khaliullin, Rustam Z. & Bell, Alexis T. September 5, 2002.

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Density functional theory was used to investigate the mechanism and kinetics of methanol oxidation to formaldehyde over vanadia supported on silica, titania, and zirconia. The catalytically active site was modeled as an isolated VO{sub 4} unit attached to the support. The calculated geometry and vibrational frequencies of the active site are in good agreement with experimental measurements both for model compounds and oxide-supported vanadia. Methanol adsorption is found to occur preferentially with the rupture of a V-O-M bond (M = Si, Ti, Zr) and with preferential attachment of a methoxy group to V. The vibrational frequencies of the methoxy group are in good agreement with those observed experimentally as are the calculated isobars. The formation of formaldehyde is assumed to occur via the transfer of an H atom of a methoxy group to the O atom of the V=O group. The activation energy for this process is found to be in the range of 199-214 kJ/mol and apparent activation energies for the overall oxidation of methanol to formaldehyde are predicted to lie in the range of 112-123 kJ/mol, which is significantly higher than that found experimentally. Moreover, the predicted turnover frequency (TOF) for methanol oxidation is found to be essentially independent of support composition, whereas experiments show that the TOF is 10{sup 3} greater for titania- and zirconia-supported vanadia than for silica-supported vanadia. Based on these findings, it is proposed that the formation of formaldehyde from methoxy groups may require pairs of adjacent VO{sub 4} groups or V{sub 2}O{sub 7} dimer structures.

Physical Description

29 pages

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OSTI as DE00836790

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  • Journal Name: Journal of Physical Chemistry B; Journal Volume: 106; Journal Issue: 32; Other Information: Submitted to Journal of Physical Chemistry B: Volume 106, No.32; Journal Publication Date: 8/15/2002

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  • Report No.: LBNL-49412
  • Grant Number: AC03-76SF00098
  • DOI: 10.1021/jp014695h | External Link
  • Office of Scientific & Technical Information Report Number: 836790
  • Grant Number: RC1-2204
  • Archival Resource Key: ark:/67531/metadc785687

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  • September 5, 2002

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  • Dec. 3, 2015, 9:30 a.m.

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  • July 26, 2016, 3:31 p.m.

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Khaliullin, Rustam Z. & Bell, Alexis T. A density functional theory study of the oxidation of methanol to formaldehyde over vanadia supported on silica, titania, and zirconia, article, September 5, 2002; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc785687/: accessed August 20, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.