Mnx/SEP(海泡石)催化剂低温NH_3-SCR脱硝性能

Mnx/SEP( sepiolite) catalysts for low temperature NH_3-SCR catalytic reduction of NO

以Mn(CH_3COO)_2和KMnO_4为前驱体,采用原位生长法在海泡石(SEP)载体表面负载锰氧化物,制备Mnx/SEP催化剂应用于低温SCR脱硝反应.分别考察了制备工艺及反应条件等因素对Mnx/SEP催化剂低温NH_3-SCR脱硝活性的影响.采用BET、XRD、SEM、XPS等表征手段对催化剂的结构和形貌进行表征分析.结果表明,在锰负载量为8 wt%、n(Mn(CH_3COO)_2)/n(KMnO_4)为3∶2时所制备的催化剂具有较佳的NH_3-SCR低温脱硝活性.当空速为10000 h^(-1)、反应温度在100—250℃区间时,转化率为100%,表明该催化剂具有高空速适应性.锰氧化物活性组分在海泡石表面的均匀分布和高的分散性使催化剂具有较大的有效比表面积,有利于催化剂NH_3-SCR反应;此外n(Mn(AC)_2)/n(KMnO_4)对催化剂表面活性物种形态特别是表面Mn^(4+)/Mn^(3+)比具有显著影响,进而与催化剂的低温SCR脱硝活性紧密相关.

Sepiolite supported manganese oxides（ Mnx/SEP） catalysts for low temperature SCR were prepared by in-situ reaction with Mn（CH_3COO）_2 and KMnO_4 as precursors. Manganese oxide was produced and deposited on the surface of sepiolite（ SEP）. Dependency of the catalyst＇ s SCR activity on the preparation and reaction conditions was investigated by activity measurement. BET,XRD,SEM and XPS also were carried out for the characterization of the catalysts. Results showed that the catalyst prepared with 8 wt% Mn loading of and ratio 3∶2 Mn（CH_3COO）_2 to KMnO_4 had the highest NH_3-SCR activity at low temperatures. NO conversion was nearly 100% in the temperature range of 100—250 ℃ when the space velocity was 10000 h-1. Uniform distribution of the manganese oxide active species on the surface of the sepiolite and high dispersibility rendered the catalysts a large effective specific surface area,which was favorable for NH_3-SCR reaction over the catalysts.Furthermore, n（ Mn（ CH_3 COO）_2）/n（ KMnO_4） showed significant influence on the surfacemorphology of the catalyst,especially for the ratio of Mn^（4＋）/Mn^（3＋） on the surface,and was closely related to the low temperature SCR denitrification activity of the catalyst.