Physicochemical properties of MoO sub 3 -TiO sub 2 prepared by an equilibrium adsorption method
- Sophia Univ., Tokyo (Japan)
- Lehigh Univ., Bethlehem, PA (USA)
The adsorption phenomena of molybdena species onto titania surfaces and the surface properties of the catalysts have been studied by using an equilibrium adsorption method. {sup 95}Mo NMR and UV spectroscopic studies show that the aqueous molybdena species vary as a function of the pH of the impregnating solution. For acidic pH values, polymeric species, Mo{sub 7}O{sub 24}{sup 6{minus}} ions, are present, while in the basic solutions it is the monomeric MoO{sub 4}{sup 2{minus}} ions that are present. The adsorbed amounts of molybdate anion are strongly dependent on the pH of the impregnating solution and increase as an inverse function of the pH. XRD, Raman, and XPS data of the calcined samples show that monolayer coverage of molybdenum oxide is established at pH 3.98 (6.6 wt%). The Raman studies reveal that the molybdenum oxide monolayer is composed of distorted octahedra. At more acidic pH regions, pH < 3.98, crystalline MoO{sub 3} is formed above monolayer coverage. The result of catalytic oxidation of methanol show that the catalysts up to monolayer coverage of surface molybdate species possess higher turnover numbers than the catalysts possessing more than monolayer coverage (presence of crystalline MoO{sub 3}). The primary methanol oxidation product is dimethoxymethane at low conversions; methyl formate is next in abundance. The selectivity for dimethyl ether, which occurred as a side reaction on the acidic sites of catalysts, increases as the Mo loading increases.
- OSTI ID:
- 6783122
- Journal Information:
- Journal of Catalysis; (USA), Journal Name: Journal of Catalysis; (USA) Vol. 120:2; ISSN 0021-9517; ISSN JCTLA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
020400 -- Petroleum-- Processing
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ADSORPTION
ALCOHOLS
CATALYSTS
CATALYTIC CRACKING
CHALCOGENIDES
CHEMICAL PREPARATION
CHEMICAL REACTIONS
COHERENT SCATTERING
CRACKING
CRYSTAL STRUCTURE
DECOMPOSITION
DESULFURIZATION
DIFFRACTION
ELECTRON SPECTROSCOPY
EVEN-ODD NUCLEI
HYDROXY COMPOUNDS
IMPREGNATION
INTERMEDIATE MASS NUCLEI
ISOTOPES
LASER SPECTROSCOPY
LAYERS
MAGNETIC RESONANCE
METHANOL
MOLYBDENUM 95
MOLYBDENUM COMPOUNDS
MOLYBDENUM ISOTOPES
MOLYBDENUM OXIDES
NUCLEAR MAGNETIC RESONANCE
NUCLEI
ORGANIC COMPOUNDS
OXIDATION
OXIDES
OXYGEN COMPOUNDS
PH VALUE
PHOTOELECTRON SPECTROSCOPY
PYROLYSIS
RAMAN SPECTROSCOPY
REFRACTORY METAL COMPOUNDS
RESONANCE
SCATTERING
SORPTION
SPECTRA
SPECTROSCOPY
STABLE ISOTOPES
SURFACE PROPERTIES
SYNTHESIS
THERMOCHEMICAL PROCESSES
TITANIUM COMPOUNDS
TITANIUM OXIDES
TRANSITION ELEMENT COMPOUNDS
ULTRAVIOLET SPECTRA
X-RAY DIFFRACTION
X-RAY SPECTROSCOPY