Insight to the Cooperation between Electronic Unsaturated Metal Sites and Hydroxyl Species Improves the So2 Resistance of Fe-Mno2@Tio2 for Simultaneous Removal of Toluene and No

Abstract:
Removing volatile organic compounds (VOCs) and nitrogen oxides (NOx) simultaneously from sulfur-containing complex flue gases is a significant challenge. To address the issue of Fe-MnO2 catalyst deactivation due to SO2 poisoning, a core-shell Fe-MnO2@TiO2 catalyst is developed. The catalyst can simultaneously remove toluene and NO from SO2-containing flue gas at 200-350 °C. Thermogravimetric analysis shows that the TiO2 shell substantially reduces SO2 deposition on the catalyst surface. X-ray photoelectron spectroscopy (XPS) and in situ Raman analyses reveal that TiO2 modifies the electronic structure of the catalyst, causing the electron cloud density of Ti towards Fe and Mn. Electron-deficient Ti sites are formed, which are preferentially attacked by SO2. In addition, in situ diffuse reflectance Fourier transform infrared spectroscopy (in situ DRIFTS) shows that introducing Ti creates bridging hydroxyl groups with oxidizing capabilities on the Fe-MnO2@TiO2 surface. Under the synergistic effect of coordination-unsaturated Ti sites and bridging hydroxyl groups, SO2 is oxidized to sulfates and retained on the TiO2 shell, thereby protecting the Fe and Mn sites from poisoning. This study reveals the mechanism by which Ti enhances the sulfur resistance of Mn-based catalysts, providing theoretical insights for the design of sulfur-resistant catalysts.

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