Selective catalytic reaction of NOx with NH3 over Ce–Fe/TiO2-loaded wire-mesh honeycomb: Resistance to SO2 poisoning

Abstract Ce–Fe/TiO2/Al2O3/wire-mesh honeycomb catalyst (Ce–Fe/WMH) exhibited a high activity for the selective catalytic reduction (SCR) of NOx in SO2-containing gases. Analysis of fresh and spent catalysts by XRD, BET, XPS, TG and FTIR indicated that Ce sites were sulfated preferentially over Ce–Fe/WMH during the SCR reaction in the presence of SO2, which could increase the amount of surface active oxygen species. On the other hand, the formation of surface hydroxyls due to the hydration of SO42− could supply more Bronsted acid sites to adsorb NH3 in the form of NH4+. These two factors played significant roles in the good SO2 durability of Ce–Fe/WMH. In addition, the sulfation of CeO2 on catalyst surface might approach a stable state upon certain amount of SO2 in reactant gas. The reaction mechanism study showed that only Eley–Rideal reaction pathway between ionic NH4+, coordinated NH3 and gaseous NO dominated in the reaction; the Langmuir–Hinshelwood reaction pathway was cut off by the sulfation, resulting in the rapid decrease of NOx conversion in the early period of SCR reaction in the presence of SO2.