Physicochemical properties of MoO sub 3 -TiO sub 2 prepared by an equilibrium adsorption method

Journal Article · Fri Dec 01 00:00:00 EST 1989 · Journal of Catalysis; (USA)

DOI:https://doi.org/10.1016/0021-9517(89)90273-X· OSTI ID:6783122

Kim, Du Soung; Kurusu, Yasuhiko; Segawa, Kohichi ^[1]; Wachs, I E; Hardcastle, F D ^[2]

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1. Sophia Univ., Tokyo (Japan)
2. 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), Vol. 120:2; ISSN 0021-9517
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
02 PETROLEUM
MOLYBDENUM OXIDES
SURFACE PROPERTIES
TITANIUM OXIDES
ADSORPTION
CATALYSTS
CATALYTIC CRACKING
CHEMICAL PREPARATION
CRYSTAL STRUCTURE
DESULFURIZATION
IMPREGNATION
LAYERS
METHANOL
MOLYBDENUM 95
NUCLEAR MAGNETIC RESONANCE
OXIDATION
PH VALUE
PHOTOELECTRON SPECTROSCOPY
RAMAN SPECTROSCOPY
ULTRAVIOLET SPECTRA
X-RAY DIFFRACTION
X-RAY SPECTROSCOPY
ALCOHOLS
CHALCOGENIDES
CHEMICAL REACTIONS
COHERENT SCATTERING
CRACKING
DECOMPOSITION
DIFFRACTION
ELECTRON SPECTROSCOPY
EVEN-ODD NUCLEI
HYDROXY COMPOUNDS
INTERMEDIATE MASS NUCLEI
ISOTOPES
LASER SPECTROSCOPY
MAGNETIC RESONANCE
MOLYBDENUM COMPOUNDS
MOLYBDENUM ISOTOPES
NUCLEI
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PYROLYSIS
REFRACTORY METAL COMPOUNDS
RESONANCE
SCATTERING
SORPTION
SPECTRA
SPECTROSCOPY
STABLE ISOTOPES
SYNTHESIS
THERMOCHEMICAL PROCESSES
TITANIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
400201* - Chemical &amp; Physicochemical Properties
020400 - Petroleum- Processing