MnαTi1-α催化剂NH3选择性催化还原NO的中低温活性及机理研究

采用浸渍法制备了不同MnO_x负载量的SCR催化剂,检测其在中低温下的脱硝活性和抗SO_2中毒性能,并分析影响Mn_αTi_(1-α)催化剂中低温活性的机理。采用BET、XRD、XPS、NH_3-TPD和H_2-TPR对催化剂表征。研究表明,随着MnO_x负载量的增加,Mn_αTi_(1-α)催化剂最高脱硝活性温度区间向低温区移动,Mn_(0.1)Ti_(0.9)催化剂在200-385℃脱硝效率达80%以上。SO_2会造成Mn_αTi_(1-α)催化剂脱硝活性显著下降,且不可逆。当MnO_x负载量增加时,催化剂比表面积先增大后略微减小、H_2-TPR中Mn~(4+)峰面积增大、表面化学吸附氧增加,有利于NH_3-SCR反应在低温下的进行。Mn_αTi_(1-α)催化剂的酸性位点随MnO_x含量增加而增多,H_2还原峰出现温度较低,表明Mn_αTi_(1-α)催化剂具有良好的中低温氧化还原性。

Study on the activity and mechanism of selective catalytic reduction of NO with NH3 over MnαTi1-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.