Acidic properties of oxides containing niobia on silica and niobia in silica

Journal Article · Wed May 01 04:00:00 EDT 1991 · Journal of Catalysis; (USA)

DOI:https://doi.org/10.1016/0021-9517(91)90007-Q· OSTI ID:5530418

Burke, P A; Ko, E I ^[1]

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1. Carnegie Mellon Univ., Pittsburgh, Pennsylvania (USA)

A series of composite oxides containing niobia (Nb{sub 2}O{sub 5}) and silica (SiO{sub 2}) was prepared by either incipient wetness impregnation to form surface phase oxides or by coprecipitation to form mixed oxides. At low Nb{sub 2}O{sub 5} concentrations, both the surface phase and mixed oxides showed strong Lewis acidity as determined by thermogravimetric and infrared studies of adsorbed pyridine. A surface phase oxide containing 0.25 monolayer of Nb{sub 2}O{sub 5} on SiO{sub 2} further showed strong Broensted acidity. With increasing Nb{sub 2}O{sub 5} concentration and/or treatment temperature, Nb{sub 2}O{sub 5} in these composite oxides became more bulk-like and showed a corresponding decrease in acid strength. These acidic properties are discussed in terms of proposed structural models which contain tetrahedral niobia, octahedral niobia, and Nb=O bonds as basic building blocks.

• OSTI ID: 5530418
• Journal Information: Journal of Catalysis; (USA), Journal Name: Journal of Catalysis; (USA) Vol. 129:1; ISSN 0021-9517; ISSN JCTLA
• Country of Publication: United States
• Language: English

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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ADSORPTION
ALCOHOLS
AZINES
BROENSTED ACIDS
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CATALYSTS
CHALCOGENIDES
CHEMICAL ANALYSIS
CHEMICAL PREPARATION
CHEMICAL REACTIONS
COMPOSITE MATERIALS
COPRECIPITATION
CRYSTAL STRUCTURE
DEHYDRATION
DEHYDROGENATION
DISPERSIONS
ETHANOL
GRAVIMETRIC ANALYSIS
HETEROCYCLIC COMPOUNDS
HYDROGEN COMPOUNDS
HYDROXY COMPOUNDS
IMPREGNATION
INFRARED SPECTRA
INORGANIC ACIDS
ISOMERIZATION
LAYERS
LEWIS ACIDS
MATERIALS
METHANATION
MICROSTRUCTURE
MINERALS
MIXTURES
NIOBIUM COMPOUNDS
NIOBIUM OXIDES
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PHASE STUDIES
PRECIPITATION
PYRIDINE
PYRIDINES
QUANTITATIVE CHEMICAL ANALYSIS
QUANTITY RATIO
REFRACTORY METAL COMPOUNDS
SEPARATION PROCESSES
SILICA
SILICON COMPOUNDS
SILICON OXIDES
SORPTION
SPECTRA
SURFACE PROPERTIES
SYNTHESIS
THERMAL ANALYSIS
THERMAL GRAVIMETRIC ANALYSIS
TRANSITION ELEMENT COMPOUNDS