Performance of Mg-Ti modified iron-based catalyst in NH3-SCR of NO at the presence of arsenic: Influence of oxygen and temperature

Abstract Impact of arsenic on the performance of Mg-Ti modified iron-based catalyst during selective catalytic reduction of NOx with ammonia was studied. The results indicated that Mg and Ti modification not only improved the catalytic activity at 100–350 °C, but also exhibited remarkable anti-arsenic ability. Mg was dominant in the excellent anti-arsenic performance, and this role was firstly recognized. The anti-arsenic mechanism of Mg-Ti modified iron-based catalyst was ascribed to two aspects. One side, Mg exhibited well reactivity with arsenic which competed with Fe for the adsorption of arsenic and protected active iron sites from arsenic occupation. The other side, presence of Mg promoted the formation of MgFe2O4 in view of the strong interactions between Mg and Fe, suppressing the interactions between arsenic and Fe. Instead, gaseous arsenic turned to bond with Mg-O sites. Consequently, surface acid sites and function Fe-OH/ Fe = O bonds were preserved for de-NOx. Moreover, increase of oxygen content and temperature weakened the deactivation of Mg-Ti modified iron-based catalyst by arsenic. It was due to the oxidation of As2O3 with oxygen content increase and the strengthened reactivity of non-active iron sites with arsenic and Mg with arsenic as temperature elevation, inhibiting the interactions between active iron sites with arsenic.