Surface properties of uranium antimony mixed oxide catalysts: Xps and adsorbed phase NMR studies

Abstract

The mixed oxides of uranium and antimony are quite interesting compounds on the fundamental side, because of their electronic structure aspects, and pratically, since they are promising as hydrocarbon oxidation catalysts. There are two well-defined compounds: USb 3O 10, and USbO 5. The former is an active and selective catalyst, the latter is known to lead to total oxidation. Several samples of both oxides have been synthesized, characterized by powder X-ray diffraction, IR absorption, thermal analysis and X-ray photoelectron spectroscopy; their surfaces properties for propylene adsorption have been studied by 13C NMR spectroscopy. The preliminary conclusions of this work enlighten the importance of the synthetic pathway to the catalyst, being USbO 5 a necessary precursor for USb 3O 10. Both uranium and antimony appear to be +5. The two mixed oxides present however distinct electronic structures, mainly observed on the U4f photoelectron spectra, which will probably explain the differences in olefin adsorption and their different catalytic properties.