ESCA investigation of V2O5+TiO2 catalysts for the vapour phase oxidation of alkylpyridines
- 1 January 1979
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases
- Vol. 75, 1356-1370
- https://doi.org/10.1039/f19797501356
Abstract
Sensitivity factors for the quantitative analysis of vanadium- and titanium-oxide mixtures by ESCA have been determined from calibration curves of various V2O5+TiO2 mixtures. Sintered Ti(VO3)4 and sintered powder mixtures of V2O5 and TiO2 in various ratios yielded a higher vanadium content than the bulk composition; this is caused by the TiO2 particles being embedded in a matrix of V2O5. The unsintered Ti(VO3)4 and V2O5+TiO2 mixtures, on the other hand, gave atom ratios in good agreement with the bulk composition. The V 2p, Ti 2p and O 1s electron binding energies and half widths were measured for various oxides and oxide mixtures, both sintered and unsintered. The lower vanadium oxides were non-stoichiometric at the surface. The V2O5+TiO2 catalysts used in the oxidation of alkylpyridines were only reduced in a thin surface layer. The V2O5 was partially reduced to lower valence states while the TiO2 was unchanged, as determined by the V 2p and Ti 2p signals. The degree of reduction varied throughout the catalyst bed, with the highest reduction nearest to the reactor inlet. It was strongly dependent upon the reaction temperature and a maximum was obtained at 455°C, the same temperature which gives maximum selectivity. Surface compositional changes in V, Ti and O, caused by participating in catalysis, were observed for all the catalysts used.Keywords
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