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Characterization of silica‐supported uranium–molybdenum oxide catalysts
Author(s) -
Fierro J. L. G.,
Salazar E.,
Legarreta J. A.
Publication year - 1985
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/sia.740070208
Subject(s) - catalysis , molybdenum , molybdate , crystallite , uranium , uranyl , chemistry , oxide , inorganic chemistry , x ray photoelectron spectroscopy , nuclear chemistry , materials science , crystallography , chemical engineering , metallurgy , biochemistry , organic chemistry , engineering
The techniques of X‐ray diffraction, infrared and electron spin resonance spectroscopies, kinetics of reduction by H 2 , and XPS were used to investigate the chemical species present at the interface in silica‐supported uranium–molybdenum oxide catalysts. In this catalyst series, with constant MoO 3 loading (16.7 wt%) and Mo/(Mo + U) atomic ratios ranging between 1 and 0, it was found that the oxidic forms of Mo and U were not well dispersed, MoO 3 crystallites being detected on the catalysts with a high Mo/(Mo + U) atomic ratio. In the less‐uranium‐rich catalysts [Mo/(Mo + U) = 0.89] both MoO 3 crystallites and a crystalline ‘uranyl molybdate’ phase were present. This catalyst exhibited the highest reduction degree by H 2 and the highest ESR signal intensity of Mo 5+ ions when reduced under very mild conditions. The information obtained with these techniques was used to explain the promotional effect of U on the MoO 3 /SiO 2 base catalyst for the selective oxidation of isobutene.