Study on the activity and mechanism of selective catalytic reduction of NO with NH₃ over Mn_αTi_1-α catalyst at medium-low temperatures

Mn_αTi_1-α catalysts for selective catalytic reduction (SCR) of NO were prepared with impregnation method and their denitration activity and SO₂ resistance at medium-low temperature were evaluated. The catalysts were characterized using BET, XRD, XPS, NH₃-TPD and H₂-TPR. The results showed that the temperature range of the highest denitration activity of Mn_αTi_1-α catalyst shifted to the lower temperature zone along with the increase of MnO_x loading. The denitration efficiency of Mn_0.1Ti_0.9 catalyst reached over 80% at 200-385 ℃. SO₂ could bring down denitration activity of Mn_αTi_1-α catalyst greatly and resulted in irreversible deactivation. The specific surface area of the catalyst first increased then slightly decreased with the increase of Mn_x loading. Both Mn⁴⁺ peak area in H₂-TPR and surface chemical adsorbed oxygen increased along with the increase of MnO_x loading. All these factors were beneficial to the proceeding of NH₃-SCR reaction at low temperature. With the increase of MnO_x loading, the acid sites of Mn_αTi_1-α catalyst increased and the reduction peak at low temperature appeared, indicating that Mn_αTi_1-α catalyst had good redox performance at medium and low temperature.