Excellent sulfur tolerance performance over Fe-SO4/TiO2 catalysts for NH3-SCR: Influence of sulfation and Fe-based sulfates

Abstract

A series of Fe-SO4/TiO2 catalysts were synthesized by simple impregnation method, and their performances of the selective catalytic reduction (SCR) of NOx by NH3 were measured. Fe2(SO4)3 with the largest specific surface area exhibited the best high-temperature performance, Fe(OH)SO4 with the highest content of chemisorbed oxygen species and the lowest initial reduction temperature illustrated the best low-temperature activity, and FeSO4 presented the worst overall activity. Meanwhile, the sulfur tolerance and structure-activity relationship of Fe-SO4/TiO2 catalysts were systematically studied. Further, the active components in Fe-SO4/TiO2 catalysts were tested to be FeSO4, Fe2(SO4)3 and Fe(OH)SO4. And the optimum performance (light-off temperature at around 200 °C, NO conversion over 80% within 280–400 °C) was obtained with 20 wt% FeSO4 loading. Remarkably, 20%Fe-SO4/TiO2 catalyst was found to possess excellent sulfur tolerance due to the increased surface acidity and chemisorbed oxygen species by SO2 sulfation. In situ DRIFTs demonstrated that there were certain NH3 and NO adsorption sites on the surface of 20%Fe-SO4/TiO2 catalyst, on which the NH3-SCR reactions occurred mainly followed Langmuir-Hinshelwood (L-H) mechanism accompanied by a slight Eley-Rideal (E-R) mechanism.