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In the catalytic oxidation of volatile organic compounds, Co-based oxide catalysts show excellent potential and draw more and more attention, but SO2poisoning 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 SO2poisoning. 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 SO2to 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 SO2on Co oxides and inhibit the formation of stable sulfate species, thus effectively reducing the effect of SO2poisoning 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 SO2on the surface mainly existed in the form of surface-adsorbed SO2species. Only a small proportion of SO2could form SO3species 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 SO2poisoning.

In this work, mesoporous TiO2spheres supported MnCeW mixed oxide catalysts (MnCeW/m-TiO2) for selective catalytic reduction of NOxwith NH3were prepared by a wet impregnation method. It is interesting that the MnCeW/m-TiO2catalysts exhibited excellent SCR activity and N2selectivity in a wide temperature range, even under the high gas hourly space velocity. From in situ diffuse reflectance infrared transform spectroscopy (in situ DRIFTs) studies of desorption, it could be concluded that the addition of tungsten brought about more Brønsted acid sites and reduced the energy barrier of NOxspecies adsorbed on the surface. At high temperature range, there were still some Brønsted acid sites and NOxspecies including bidentate nitrate and nitro compounds in MnCeW/m-TiO2, therefore more intermediates could take part in the SCR reactions as well as better catalytic performance. Besides, the in situ DRIFTs of transient reactions indicated that the formed NH3species and NOxspecies of MnCeW/m-TiO2were more reactive due to the promotional effects of tungsten. A series of traditional characterizations also revealed the promotional effects of tungsten for surface active elements, catalytic redox properties, and acid sites of NH3adsorption. In a word, all the results confirmed that the introduction of W could enhance active NH3and NOxspecies as well as surface active elements, thus contributing to the catalytic performance. The present investigations may open a path for design and application of catalysts with outstanding catalytic activity and selectivity.