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.