The thermal spreading of antimony oxides onto Fe2O3

The uniform antimony-rich surface layer on Fe₂O₃ was carried out via thermal spreading of Sb₂O₃ and Sb₂O₄. TG–DTA results indicate that the oxidation temperature of Sb₂O₃ was decreased ca. 100 K due to thermal spreading effect. Although Sb₂O₄ is almost catalytically inert for oxidation of isobutane and Fe₂O₃ is a typical non-selective catalyst for this reaction, the formation of antimony-rich layer suppresses the combustion reactions and favors the partial oxidation reactions. When Sb₂O₄ instead of Sb₂O₃ was used as antimony resource, the enrichment of antimony on Fe₂O₃ surface was much lower. However, the reaction atmosphere of isobutane oxidation enhances antimony spreading over Fe₂O₃ surface. According to Mars–Van Krevelen mechanism, some Sb₂O₄ in catalysts could be intermediately reduced into Sb₂O₃ during reaction of isobutene oxidation, which thermal spreading is much easier. As shown by Raman results, the Sb₂O₄ that has been spread on Fe₂O₃ surface is probably amorphous.