Synthesis, characterization, and reactivity of oxide-supported molybdenum oxide
Molybdenum oxide was supported on silicon oxide, aluminum oxide, and magnesium oxide with the use of Mo({eta}{sup 3}-C{sub 3}H{sub 5}){sub 4}, Mo{sub 2}({eta}{sup 3}-C{sub 3}H{sub 5}){sub 4}, MoCl{sub 5}, (NH){sub 4}Mo{sub 7}O{sub 24}{center dot}4H{sub 2}O, H{sub 2}(MoO{sub 3}C{sub 2}O{sub 4}){center dot}2H{sub 2}O precusors. Oxidized samples were characterized with laser Raman spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The molybdenum carbonyl species formed by uv photoreduction of Mo{sup 6+}/SiO{sub 2} in CO were studied with infrared spectroscopy and temperature programmed decomposition. The relationship between Mo/SiO{sub 2} structure and catalytic behavior was studied with the structure sensitive partial oxidation of methanol. For the systems studied, the structures of the hydrated molybdate submonolayer surface species were found to be independent of the molybdenum precursor used for preparation. These structures were governed by the pH dependent polymerization chemistry of molybdate anions and the isoelectric point of the hydrated support oxides. Acidic molybdena was only weakly held on silica because of the low isoelectric point of the support, resulting in the formation of octahedrally-coordinated polymolybdates. Alumina, with a slightly basic isoelectric point, led to the formation of molybdate tetrahedra at low molybdenum loadings and polymolybdate at higher loadings. Molybdate tetrahedra were observed on basic magnesia at all loadings studied. The formation of crystalline molybdenum compounds was governed by the preparation procedure, the molybdenum content, the calcination temperature, and the support impurities.
- Research Organization:
- Texas Univ., Austin, TX (United States)
- OSTI ID:
- 6110229
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400201* -- Chemical & Physicochemical Properties
ALCOHOLS
ALKALI METAL COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CALCINATION
CALCIUM COMPOUNDS
CATALYST SUPPORTS
CATALYSTS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL ANALYSIS
CHEMICAL PREPARATION
CHEMICAL REACTIONS
COHERENT SCATTERING
CONTROL
CRYSTAL STRUCTURE
DECOMPOSITION
DIFFRACTION
ELECTROMAGNETIC RADIATION
ELECTRON SPECTROSCOPY
HYDROXY COMPOUNDS
INFRARED RADIATION
LASER SPECTROSCOPY
MAGNESIUM COMPOUNDS
MAGNESIUM OXIDES
METHANOL
MICROSTRUCTURE
MOLECULAR STRUCTURE
MOLYBDATES
MOLYBDENUM COMPOUNDS
MOLYBDENUM OXIDES
OPTICAL PROPERTIES
ORGANIC COMPOUNDS
OXIDATION
OXIDES
OXYGEN COMPOUNDS
PH VALUE
PHOTOELECTRON SPECTROSCOPY
PHYSICAL PROPERTIES
PYROLYSIS
RADIATIONS
RAMAN SPECTROSCOPY
REFLECTIVITY
REFRACTORY METAL COMPOUNDS
SCATTERING
SILICON COMPOUNDS
SILICON OXIDES
SODIUM COMPOUNDS
SPECTROSCOPY
SURFACE PROPERTIES
SYNTHESIS
TEMPERATURE CONTROL
THERMOCHEMICAL PROCESSES
TRANSITION ELEMENT COMPOUNDS
ULTRAVIOLET RADIATION
VISIBLE RADIATION
X-RAY DIFFRACTION
X-RAY SPECTROSCOPY