Journal ArticleDOI
Raman and ultraviolet spectroscopic characterization of molybdena on alumina/catalysts
TLDR
In this paper, the Raman and UV spectra indicated that adsorption on the alumina surface occurred in all cases via the MoO/sub 4/(-2) ion, probably due to locally increased pH.Abstract:
Catalysts containing 1, 3, and 8Vertical Bar3< molybdena on ..gamma..- or g-alumina were prepared by impregnating the support with (NH/sub 4/)/sub 6/Mo/sub 7/O/sub 24/ at pH 6 or 11, at which pH's molybdenum is in the octahedral Mo/sub 7/O/sub 24/(-6) form or the tetrahedral MoO/sub 4/(-2) form, respectively. The Raman and UV spectra indicated that adsorption on the alumina surface occurred in all cases via the MoO/sub 4/(-2) ion, probably due to locally increased pH. The removal of water during drying and calcination caused polymerization of the isolated tetrahedral molybdenum species into a two-dimensional Mo-O-Mo structure. The degree of polymerization depended on the molybdenum concentration, the heat treatment, and the pH of the original adsorption which influences the molybdenum distribution. The coordination number of the molybdenum in the polymeric structure, which was probably affected by the alumina surface hydroxyl density and distribution, could not be determined. Some bulk molybdenum trioxide was formed on all samples after calcination except for a 3Vertical Bar3< MoO/sub 3/ sample impregnated at pH 11.read more
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Raman and IR studies of surface metal oxide species on oxide supports: Supported metal oxide catalysts
TL;DR: In this article, the molecular structures of the surface metal oxide species are reflected in the terminal M=O and bridging M-O-M vibrations, which are typically obtained in Raman and IR characterization studies of supported metal oxide catalysts.
Journal ArticleDOI
Raman spectroscopy of monolayer-type oxide catalysts: Supported Mo oxides
TL;DR: In this paper, a monolayer catalysts based on a structural model which assumed spreading of the active oxide over the support surface were investigated by a variety of techniques, conventional bulk sampling techniques as well as by surface-sensitive electron and ion spectroscopies, in an attempt to elucidate the nature of the catalyst surface species, and to study the coordination environment of active metal center(s).
Journal ArticleDOI
Photochromism of molybdenum oxide
Tao He,Jiannian Yao +1 more
TL;DR: In this paper, the progress in all of these areas will be reviewed thoroughly, including the early stage of the research, the band structure, photochromic mechanism and the behavior of the oxide.
Journal ArticleDOI
Monitoring surface metal oxide catalytic active sites with Raman spectroscopy
TL;DR: This critical review will show the growth in the use of Raman spectroscopy in heterogeneous catalysis research, for metal oxides as well as metals, is poised to continue to exponentially grow in the coming years.
Journal ArticleDOI
A new view on the relations between tungsten and vanadium in V2O5WO3/TiO2 catalysts for the selective reduction of NO with NH3
Patrick G.W.A. Kompio,Angelika Brückner,Frank Hipler,Gerhard Auer,Elke Löffler,Wolfgang Grünert +5 more
TL;DR: The relation between tungsten and vanadium oxide species in V 2 O 5 WO 3 /TiO 2 catalysts for the selective catalytic reduction of nitrogen oxides by ammonia was studied in this article.