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EPR Studies of the Coverage Effects in TiO2(B)-Supported Vanadia Catalysts for Toluene Ammoxidation

Jansen, Susan; Tu, Yanping; Palmieri, Michael J; Sanati, Mehri LU and Andersson, Arne LU (1992) In Journal of Catalysis 138(1). p.79-89
Abstract
EPR spectroscopy has been employed to determine the nature of vanadium (+4) species in the TiO2(B)-supported vanadia catalysts. IR and EPR studies show that multiple vanadia species are observed as a function of loading. At coverages greater than 3.5 theoretical layers, the EPR signal is reminiscent of bulk V205. At lower coverages, a different magnetic species dominates the resonance and may be attributable to tetrahedral states of vanadium at the oxide interface. The spin concentration and (g) suggest two distinct vanadia phases as a function of coverage. In this study, we have also analyzed catalysts after use in ammoxidation of toluene. These samples show strikingly different features compared with the freshly prepared samples. Changes... (More)
EPR spectroscopy has been employed to determine the nature of vanadium (+4) species in the TiO2(B)-supported vanadia catalysts. IR and EPR studies show that multiple vanadia species are observed as a function of loading. At coverages greater than 3.5 theoretical layers, the EPR signal is reminiscent of bulk V205. At lower coverages, a different magnetic species dominates the resonance and may be attributable to tetrahedral states of vanadium at the oxide interface. The spin concentration and (g) suggest two distinct vanadia phases as a function of coverage. In this study, we have also analyzed catalysts after use in ammoxidation of toluene. These samples show strikingly different features compared with the freshly prepared samples. Changes in both the g-anisotropy and hyperfine coupling were observed relative to the fresh catalysts. Though EPR is not surface sensitive, inference into the nature of the catalytic surface can be made by comparison of catalysts of different coverage and studies of monolayer samples. A study of the TiO2(B)-vanadia interface was made by comparing monolayer catalysts prepared from slightly different technique. Our measurements show strikingly different features in V4+ species as a function of preparation. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of Catalysis
volume
138
issue
1
pages
79 - 89
publisher
Elsevier
external identifiers
  • WOS:A1992JU77700007
  • Scopus:0002416187
ISSN
1090-2694
DOI
10.1016/0021-9517(92)90008-6
language
English
LU publication?
yes
id
5ab4c541-c335-4170-b406-08a174fc6b4d (old id 2017970)
date added to LUP
2011-07-05 13:11:39
date last changed
2017-01-01 08:04:16
@article{5ab4c541-c335-4170-b406-08a174fc6b4d,
  abstract     = {EPR spectroscopy has been employed to determine the nature of vanadium (+4) species in the TiO2(B)-supported vanadia catalysts. IR and EPR studies show that multiple vanadia species are observed as a function of loading. At coverages greater than 3.5 theoretical layers, the EPR signal is reminiscent of bulk V205. At lower coverages, a different magnetic species dominates the resonance and may be attributable to tetrahedral states of vanadium at the oxide interface. The spin concentration and (g) suggest two distinct vanadia phases as a function of coverage. In this study, we have also analyzed catalysts after use in ammoxidation of toluene. These samples show strikingly different features compared with the freshly prepared samples. Changes in both the g-anisotropy and hyperfine coupling were observed relative to the fresh catalysts. Though EPR is not surface sensitive, inference into the nature of the catalytic surface can be made by comparison of catalysts of different coverage and studies of monolayer samples. A study of the TiO2(B)-vanadia interface was made by comparing monolayer catalysts prepared from slightly different technique. Our measurements show strikingly different features in V4+ species as a function of preparation.},
  author       = {Jansen, Susan and Tu, Yanping and Palmieri, Michael J and Sanati, Mehri and Andersson, Arne},
  issn         = {1090-2694},
  language     = {eng},
  number       = {1},
  pages        = {79--89},
  publisher    = {Elsevier},
  series       = {Journal of Catalysis},
  title        = {EPR Studies of the Coverage Effects in TiO2(B)-Supported Vanadia Catalysts for Toluene Ammoxidation},
  url          = {http://dx.doi.org/10.1016/0021-9517(92)90008-6},
  volume       = {138},
  year         = {1992},
}