New Insight into Inhibition effect of SO 2 and H 2 O on deNO x Performance of FeTi Catalyst Prepared by a CTAB-Assisted Process

FeTi catalysts prepared by a CTAB-assisted process exhibited good resistance to H2O and SO2 when tested in the selective catalytic reduction (SCR) at low temperatures. The physicochemical properties of the catalysts and the NO reaction behaviour under the influence of H2O and SO2 were extensively characterized using BET, TEM, TPD-MASS, TPSR and in-situ DRIFTS. It was found that catalyst deactivation in the early stage of H2O and SO2 introduction was mainly caused by pore plugging, resulting from the ammonium-sulfate salts deposition, while the active phase sulfation and competitive adsorption became the dominant catalyst-inhibiting factors in the later stage. SO2 not only greatly inhibited NO adsorption on the catalyst surface, hindering the reaction through the Langmuir–Hinshelwood path, but also inhibited the reaction between adsorbed NH3 and NO (Eley–Rideal path). Moreover, H2O promoted the transformation of NH4HSO4 to (NH4)2SO4, suggesting the “combined inhibition” of SO2 and H2O, which was also reflected by in-situ DRIFTS that a clear increase of NH3 adsorbed sites and sulfate species could be detected, thus resulting in more serious deactivation.