Surface spectroscopic study of molybdenum-alumina catalysts using x-ray photoelectron, ion-scattering, and Raman spectroscopies
X-ray photoelectron spectroscopy (ESCA,XPS), low-energy ion-scattering spectroscopy (ISS), and laser Raman spectroscopy have been used to characterize a series of MoO/sub 3//..gamma..-Al/sub 2/O/sub 3/ catalysts. Laser Raman spectroscopy has shown the presence of three distinctly different molybdenum species. At low concentrations an interaction species, possibly resulting from the reaction of molybdic acid with surface hydoxyl groups, is found. ESCA and ISS have identified the presence of both tetrahedrally and octahedrally coordinated molybdenum, the latter being present above 4 wt % MoO/sub 3/. After monolayer coverage have been reached, Al/sub 2/(MoO/sub 4/)/sub 3/ is formed and, at higher concentrations, bulk MoO/sub 3/ is observed. Below monolayer coverage discrete compound formation by Mo does not occur; geometrical configurations are determined by sites of the ..gamma..-alumina lattice. The effects of both calcination time and calcination temperature have been studied; it was found that both increased calcination temperature and calcination time favor the formation of Al/sub 2/(MoO/sub 4/)/sub 3/.
- Research Organization:
- Univ. of Pittsburgh, PA
- OSTI ID:
- 7038205
- Journal Information:
- J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 84:22; ISSN JPCHA
- Country of Publication:
- United States
- Language:
- English
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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
BINDING ENERGY
CALCINATION
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL REACTIONS
DECOMPOSITION
DESULFURIZATION
ELECTRON SPECTROSCOPY
ENERGY
ION SPECTROSCOPY
LASER SPECTROSCOPY
MOLYBDATES
MOLYBDENUM COMPOUNDS
MOLYBDENUM OXIDES
OXIDES
OXYGEN COMPOUNDS
PHOTOELECTRON SPECTROSCOPY
PYROLYSIS
RAMAN SPECTRA
SPECTRA
SPECTROSCOPY
STRUCTURAL CHEMICAL ANALYSIS
TEMPERATURE EFFECTS
THERMOCHEMICAL PROCESSES
TRANSITION ELEMENT COMPOUNDS