Fe and/or Mn oxides supported on fly ash-derived SBA-15 for low-temperature NH3-SCR

Fe and/or Mn/SBA-15 catalysts were prepared by the impregnation method using low-cost fly ash-derived SBA-15 molecular sieve as support and tested towards NH3-SCR. Powder XRD, N-2 adsorption, XPS, H-2-TPR and SEM techniques were used for catalyst characterization and investigation of relationships with the catalytic activity. The Fe-Mn/SBA-15 catalyst exhibited significantly higher NH3-SCR activities than Mn/SBA-15 or Fe/SBA-15 in the 150-250 degrees C range owing to some developed synergistic effects between Mn and Fe. In particular, the addition of Mn improved the dispersion of Fe2O3 on the catalyst surface, while the addition of Fe promoted the formation of single beta-MnO2 phase. The high dispersion of Fe2O3 , the appropriate Mn4+/Mn3+ ratio, the concentration of adsorbed oxygen and the low-T enhanced redox activity of the Fe-Mn/SBA-15 improved its NH3-SCR activity. This work opens new avenues of recycling fly ash formed in coal-fired power plants (reducing environmental pollution) and developing low-cost SCR catalysts for NOx pollution control.