前驱体对锰基SCR催化剂低温脱硝活性的影响

Effect of precursors on the performance of Mn-based catalysts for low temperature SCR of NO by NH_3

文章以凹凸棒石-活性炭(PG-AC)复合材料为载体,采用等体积浸渍法制备了一系列锰氧化物负载型催化剂(MnOx/PG-AC)用于低温烟气选择性催化还原(SCR)脱硝。对比以硝酸锰(MN)、醋酸锰(MA)2种活性组分前驱体物种制备的催化剂的SCR脱硝活性,探讨前驱体物种对催化剂低温脱硝活性的影响;采用N2-BET、XRD、XPS、FESEM等表征方法对催化剂结构特性进行表征。结果表明:以硝酸锰为前驱体制备的催化剂表现出较好的低温脱硝性能,在200℃条件下,NO转化率可达92%,而以醋酸锰为前驱体制备的催化剂在相同条件下仅为75%;BET分析结果表明,以硝酸锰为前驱体所制备催化剂的BET比表面积略高于醋酸锰;而XPS结果则显示两者的表面Mn原子浓度相近,但在300℃条件下,前者的表面锰氧化物的形态主要是Mn2O3,后者的表面锰氧化物为MnO;前驱体物种的不同可直接导致表面活性物种的形态差异,表面锰氧化物以Mn2O3的存在相比于MnO更具SCR活性。

Taking the palygorskite-activated carbon（PG-AC） as the carrier ,and by using incipient wetness impregnation method ,manganese oxides supported on the PG-AC catalysts were prepared from two different precursors ,manganese nitrate（MN） and manganese acetate（MA） ,and the effect of pre-cursors on low-temperature deNOx activity was further investigated .All the samples were characterized by means of N2-BET ,XRD ,XPS and FESEM techniques .The results reveal that the low-temperature activity of MnOx/PG-AC using MN as precursor is superior to that of MA precursor .The NO conversion of Mn8/PG-AC/MN can reach up to 92% at 200 ℃ ,however ,at the same condition , that of Mn8/PG-AC/MA can reach up to 75% .The results of BET analysis indicate that the specific surface area of M n8/PG-AC/M N is larger than that of M n8/PG-AC/M A .In the view of the results of XRD and XPS ,MnOx/PG-AC catalyst from the MN precursor at 300 ℃ results mainly in Mn2O3 , however ,MnOx/PG-AC from the MA precursor exists primarily in MnO .Meanwhile ,the surface atomic concentration of Mn obtained from two different precursors are similar .Consequently , the higher low-temperature activity over MnOx/PG-AC catalyst from the MN is attributed to different active components ,the specific surface area as well as the structure of carrier .