Insights into Boosting SO2 Tolerance for Catalytic Oxidation of Propane over Fe2O3-Promoted Co3O4/Halloysite Catalysts

In the catalytic oxidation of volatile organic compounds, Co-based oxide catalysts show excellent potential and draw more and more attention, but SO2 poisoning in actual applications is one of the key problems to be solved. In this work, a series of treated halloysite (HLS)-supported Fe-modified Co oxide catalysts were prepared. In the catalytic oxidation of propane, the catalysts with 15 wt % Co loading amounts showed the best catalytic activity, while 2 wt % Fe modifications showed the best promotional effects. The introduction of Fe not only improved the catalyst activity but also enhanced the tolerance to SO2 poisoning. Various characterizations of physical–chemical properties, in situ diffuse reflectance infrared transform spectroscopy, and density functional theory calculation results showed that the active components of Co/HLS catalysts reacted with SO2 to form sulfate species, which could not provide sufficient catalytic activity afterward. The Fe species in Fe–Co/HLS catalysts could reduce the strong adsorption of SO2 on Co oxides and inhibit the formation of stable sulfate species, thus effectively reducing the effect of SO2 poisoning on the catalysts. Furthermore, the adsorption of reactants and the formation of intermediates proceeded on the surface of Fe–Co/HLS catalysts with a greater efficiency, and SO2 on the surface mainly existed in the form of surface-adsorbed SO2 species. Only a small proportion of SO2 could form SO3 species and sulfate species, thus achieving the purpose of protecting the active sites and maintaining the catalytic activity. The present study of halloysite-supported Fe-modified Co oxide catalysts would provide help for the development of Co oxide catalysts with excellent catalytic performance and tolerance to SO2 poisoning.