EPR study of the coordination sphere of Mo sup 5+ ions in UV-irradiated silica-supported molybdenum catalysts

Journal Article · Sun Sep 01 04:00:00 EDT 1991 · Journal of Catalysis; (United States)

DOI:https://doi.org/10.1016/0021-9517(91)90349-9· OSTI ID:5544744

Canose, B; Gonzalez-Elipe, A R ^[1]; Che, M ^[2]

---

1. Univ. de Sevilla (Spain)
2. Univ. Pierre et Marie Curie, Paris (France)

The determination of the number of coordination vacancies existing at transition metal cations at the surface of bulk or supported oxides is of greater interest in relation to the adsorption and catalytic properties of such systems. In the case of paramagnetic cations, the authors have developed a method consisting of the recording of their first and third derivative EPR spectra after adsorption of {sup 13}CO, ({sup 13}C, I = 1/2). In this way, the {sup 13}C superhyperfine structure which is normally observed permits the determination of the number of CO molecules bonded to the metal center. In a recent EPR work published in this journal, Seyedmonir and Howe have reported the formation of a CO adduct of the tetrahedral Mo{sup 5+}-OH{sup {minus}} species formed by UV-irradiation at 20 K of a MoO{sub 3}/SiO{sub 2} catalyst in the presence of H{sub 2}. In that work, although the structure of such an adduct could not be derived unambiguously on the basis of the g tensor values, the coordination of the Mo{sup 5+} ion by two CO molecules was suggested. This would be in agreement with the previous results with thermally reduced V{sub 2}O{sub 5}/SiO{sub 2} and MoO{sub 3}/SiO{sub 2} catalysts, where the coordination of, respectively, V{sup 4+} and Mo{sup 5+} tetrahedral centers by two CO molecules was proven by means of the combined use of {sup 13}CO and third derivative EPR spectra. In the present work, using this approach, they have studied the structure of these Mo{sup 5+} ions photochemically generated on MoO{sub 3}/SiO{sub 2} catalysts and concluded that only one CO molecule is bonded to the paramagnetic ion.

• OSTI ID: 5544744
• Journal Information: Journal of Catalysis; (United States), Journal Name: Journal of Catalysis; (United States) Vol. 131:1; ISSN 0021-9517; ISSN JCTLA
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360602* -- Other Materials-- Structure & Phase Studies
360605 -- Materials-- Radiation Effects
ADSORPTION
CARBON 13
CARBON COMPOUNDS
CARBON ISOTOPES
CARBON MONOXIDE
CARBON OXIDES
CATALYST SUPPORTS
CATALYSTS
CATALYTIC EFFECTS
CHALCOGENIDES
ELECTROMAGNETIC RADIATION
ELECTRON SPIN RESONANCE
ELECTRONIC STRUCTURE
EVEN-ODD NUCLEI
IRRADIATION
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
MINERALS
MOLECULAR STRUCTURE
MOLYBDENUM COMPOUNDS
NUCLEI
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL RADIATION EFFECTS
RADIATION EFFECTS
RADIATIONS
REFRACTORY METAL COMPOUNDS
RESONANCE
SILICA
SILICON COMPOUNDS
SILICON OXIDES
SORPTION
SORPTIVE PROPERTIES
STABLE ISOTOPES
SURFACE PROPERTIES
TRANSITION ELEMENT COMPOUNDS
ULTRAVIOLET RADIATION