Surface spectroscopic study of sulfided molybdena-alumina catalysts
X-ray photoelectron spectroscopy (ESCA), low-energy ion-scattering spectroscopy (ISS), and X-ray diffraction have been used to characterize a series of sulfided and reduced MoO/sub 3//..gamma..-Al/sub 2/O/sub 3/ catalysts. X-ray diffraction has shown the presence of small MoS/sub 2/ crystallites on a catalyst prepared by impregnation of ammonium thiomolybdate in ..gamma..-alumina with subsequent calcination. ESCA and ISS have identified the presence of both MoS/sub 2/ and Mo(V) on a MoO/sub 3//..gamma..-Al/sub 2/O/sub 3/ catalyst sulfided with 15% H/sub 2/S/H/sub 2/. The octahedrally and tetrahedrally coordinated molybdenum on an oxidic MoO/sub 3//..gamma..-Al/sub 2/O/sub 3/ precursor catalyst show different sulfidation behavior. At low Mo concentrations, tetrahedrally coordinated molybdenum is reduced mostly to Mo(V) and only partially sulfided to MoS/sub 2/. Increasing the MoO/sub 3/ loading above 8% MoO/sub 3/ caused formation of excess octahedrally coordinated molybdenum which leads to a significant increase of MoS/sub 2/ on the sulfided catalyst. After monolayer coverage has been reached, formation of Al/sub 2/(MoO/sub 4/)/sub 3/ and MoO/sub 3/ result in prominent MoS/sub 2/ formation and a small amount of Mo(V) on the sulfided catalyst. The effect of calcination temperature has been studied; it was found that decreased calcination temperatures favor formation of MoS/sub 2/ on sulfided MoO/sub 3//..gamma..-Al/sub 2/O/sub 3/ catalysts.
- Research Organization:
- Univ. of Pittsburgh, PA
- DOE Contract Number:
- AC02-79ER10485
- OSTI ID:
- 5130706
- Journal Information:
- J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 88:3; 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
CATALYSTS
CHALCOGENIDES
CHEMICAL ANALYSIS
CHEMICAL REACTIONS
COHERENT SCATTERING
CRYSTALS
DESULFURIZATION
DIFFRACTION
ELECTRON SPECTROSCOPY
ION SCATTERING ANALYSIS
MOLYBDENUM COMPOUNDS
MOLYBDENUM OXIDES
MOLYBDENUM SULFIDES
NONDESTRUCTIVE ANALYSIS
OXIDES
OXYGEN COMPOUNDS
PHOTOELECTRON SPECTROSCOPY
SCATTERING
SPECTROSCOPY
SULFIDES
SULFUR COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
X-RAY DIFFRACTION