X-ray photoelectron spectroscopy study of uranium and antimony mixed metal-oxide catalysts

Abstract

X-ray photoelectron spectra of the mixed oxides USb₃O₁₀ and USbO₅ have been studied and compared with the spectra of the pure oxides β-Sb₂O₄, Sb₂O₃, Sb₂O₅ and β-UO₃, U₃O₈, UO₂. The results of this study support the view that the metals in the two compounds are in the states U^V and Sb^V.

We also discuss composition, homogeneity and finally changes in USb₃O₁₀ after its use as a catalyst in the selective oxidation of propene, and after treatment with propene and oxygen. The compound is partly reduced and can be written as U^VSb^{(III + V)}₃O_{7, 5–9}. As no cation migration was detected in the depth analysed, the initial structure of USb₃O₁₀ is not destroyed. The evolution corresponds to the formation of oxygen vacancies and to a change in the coordination of the two cations. The reduction of the initial compound is non-reversible. Our results show that oxygen mobility through the oxide is low, since reoxidation affects only the surface antimony species which are detected by Auger photoelectron spectra.