Laser Raman spectroscopy of supported vanadium oxide catalysts

Supported vanadia catalysts were studied by Raman spectroscopy to establish the effects of vanadia loading and support composition on the structure of the dispersed vanadia species. Three types of vanadia species were found to be present on SiO{sub 2}, TiO{sub 2}, and Al{sub 2}O{sub 3} supports: mon...

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Bibliographic Details
Published in:Journal of physical chemistry (1952) 1990-05, Vol.94 (10), p.4240-4246
Main Authors: Went, Gregory T, Oyama, S. Ted, Bell, Alexis T
Format: Article
Language:English
Subjects:
400201 - Chemical & Physicochemical Properties
CATALYSTS
CHALCOGENIDES
Chemistry
DATA
DATA ANALYSIS
Exact sciences and technology
EXPERIMENTAL DATA
General and physical chemistry
INFORMATION
INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY
LASER SPECTROSCOPY
MEASURING INSTRUMENTS
MEASURING METHODS
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
RAMAN SPECTROSCOPY
SPECTROSCOPY
Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry
TRANSITION ELEMENT COMPOUNDS
VANADIUM COMPOUNDS
VANADIUM OXIDES
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Summary:Supported vanadia catalysts were studied by Raman spectroscopy to establish the effects of vanadia loading and support composition on the structure of the dispersed vanadia species. Three types of vanadia species were found to be present on SiO{sub 2}, TiO{sub 2}, and Al{sub 2}O{sub 3} supports: monomeric vanadyls, one- and two-dimensional vanadate chains, and crystallites of V{sub 2}O{sub 5}. Monomeric vanadyls are characterized by a narrow Raman band in the region of 1,026-1,042 cm{sup {minus}1}, the position being sensitive to the identity of the support. The terminal V{double bond}O groups of polyvanadate chains give rise to a broad feature in the region of 800-1,000 cm{sup {minus}1} which, in the case of TiO{sub 2}-supported V{sub 2}O{sub 5}, shifts to higher frequency as the V{sub 2}O{sub 5} loading increases. Crystalline V{sub 2}O{sub 5} was detected at higher loadings on all three supports. Evidence from Raman spectroscopy and O{sub 2} chemisorption indicates that the dispersion of vanadia increases in the order SiO{sub 2} < Al{sub 2}O{sub 3} {approximately} TiO{sub 2}.
ISSN:0022-3654
1541-5740
DOI:10.1021/j100373a067