Characterization and modeling of the Mo species in grafted Mo/SiO[sub 2] catalysts after redox thermal treatments

Journal Article · Tue Jun 01 04:00:00 EDT 1993 · Journal of Catalysis; (United States)

DOI:https://doi.org/10.1006/jcat.1993.1154· OSTI ID:6154273

Louis, C; Che, M ^[1]; Anpo, Masakazu ^[2]

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1. Universite Pierre et Marie Curie, Cedex (France)
2. Univ. of Osaka Prefecture, Sakai, Osaka (Japan)

The physicochemical properties of the Mo/SiO[sub 2] catalysts prepared by the grafting method, i.e., by air- and water-free reaction between MoCl[sub 5] and hydroxyl groups of silica support followed by a washing step, are compared to those of impregnated Mo/SiO[sub 2] catalysts. Molybdenum solubility and reducibility measurements show that grafted Mo interacts more strongly with silica support than impregnated Mo. Several techniques (Mo[sup 5-] dispersion measurement by EPR spectroscopy, photoluminescence, methanol oxidation reaction, IR study of CO adsorption) indicate that Mo is better dispersed on the silica surface of grafted samples than of impregnated catalysts. The differences are more important at higher Mo loading (about 1 wt%). On the basis of these results and of those given by the literature, models for the Mo species of the oxidized grafted and impregnated catalysts are proposed. The mechanism of thermal reduction under H[sub 2] is also investigated for grafted Mo/SiO[sub 2] catalysts. An attempt to the rationalization of the changes in the coordination sphere of the Mo[sup 5-] ions observed by EPR after grafting leads to propose different types of bondings with silica (ionocovalent and coordinative) and to the formation of Mo[double bond]O molybdenyl bonds pointing outward. 65 refs., 4 figs., 3 tabs.

• OSTI ID: 6154273
• Journal Information: Journal of Catalysis; (United States), Journal Name: Journal of Catalysis; (United States) Vol. 141:2; ISSN 0021-9517; ISSN JCTLA5
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ABSORPTION SPECTROSCOPY
ADSORPTION
ALCOHOLS
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CATALYST SUPPORTS
CATALYSTS
CHALCOGENIDES
CHARGED PARTICLES
CHEMICAL REACTIONS
ELECTRON SPIN RESONANCE
ELEMENTS
HYDROGEN
HYDROXY COMPOUNDS
IONS
LUMINESCENCE
MAGNETIC RESONANCE
METALS
METHANOL
MINERALS
MOLYBDENUM
NONMETALS
ORGANIC COMPOUNDS
OXIDATION
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PHOTOLUMINESCENCE
REDUCTION
RESONANCE
SILICA
SILICON COMPOUNDS
SILICON OXIDES
SORPTION
SPECTROSCOPY
STRUCTURAL CHEMICAL ANALYSIS
TRANSITION ELEMENTS