The facilitating effect of sulfide treatment coupled sol-gel method on NH3-SCR activity of Fe–Mn/TiO2 catalysts

Abstract

The 5Fe–3Mn–S/TiO2-SG catalysts were synthesized by sulfide treatment coupled sol-gel method to develop new NH3-SCR catalysts with wide temperature window, good low-temperature activity and environment-friendly. The evolution of catalyst surface chemical state, morphology, structure, acidity and interaction forces were systematically investigated by XPS, BET, XRD, SEM, H2-TPR, NH3-TPD, UV, IR and steady-state kinetic tests. The influence of sulfide treatment coupled sol-gel method on NO conversion was explored. XRD, BET and SEM characterization revealed that sulfide treatment resulted in smaller catalyst particles and higher dispersion, which increased the specific surface area. XPS, NH3-TPD and steady-state kinetic tests results demonstrated that the sulfide treatment catalysts had a higher surface adsorbed oxygen (Oα) content, which could produce more oxygen vacancies on the catalyst surface, thus increasing the number of acid sites. H2-TPR and UV results demonstrated that the 5Fe–3Mn–S/TiO2-SG catalysts exhibited the strongest contact between the carrier and the active component. The 5Fe–3Mn–S/TiO2-SG catalyst obtained more than 80% NO conversion in the operational temperature range of 220–420 °C, according to the NH3-SCR reaction data. The temperature window was expanded by 120 °C compared to conventional Fe–Mn/TiO2 catalysts, and 98% conversion was achieved at 300 °C. Meanwhile, DFT calculations of the SO42--MnFe2O4(311) crystalline surface of the 5Fe–3Mn–S/TiO2-SG catalysts revealed that it could form stronger chemisorption for both NH3 and NO, which promoted the NH3-SCR reaction more effectively. The DFT calculation results and the experimental findings agreed well.