Raman and ultraviolet spectroscopic characterization of molybdena on alumina/catalysts
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.
- Research Organization:
- Univ. of Muenchen
- OSTI ID:
- 6873543
- Journal Information:
- J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 83:9; ISSN JPCHA
- Country of Publication:
- United States
- Language:
- English
Similar Records
Surface spectroscopic study of molybdena/alumina catalysts using X-ray photoelectron, ion-scattering, and Raman spectroscopies
sup 95 Mo NMR study of the interaction of heptamolybdate solutions with alumina and silica
Related Subjects
400201* -- Chemical & Physicochemical Properties
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CALCINATION
CATALYST SUPPORTS
CATALYSTS
CHALCOGENIDES
CHEMICAL PREPARATION
CHEMICAL REACTIONS
CRYSTAL STRUCTURE
DECOMPOSITION
MICROSTRUCTURE
MOLYBDENUM COMPOUNDS
MOLYBDENUM OXIDES
OXIDES
OXYGEN COMPOUNDS
PH VALUE
POLYMERIZATION
PYROLYSIS
RAMAN SPECTRA
SPECTRA
STRUCTURAL CHEMICAL ANALYSIS
SYNTHESIS
TEMPERATURE EFFECTS
THERMOCHEMICAL PROCESSES
TRANSITION ELEMENT COMPOUNDS
ULTRAVIOLET SPECTRA