%0 Journal Article
%T <br>
%A 刘小青
%A 喻成龙
%A 孙梦婷
%A 李时卉
%A 黄碧纯
%J 物理化学学报
%D 2016
%R 10.3866/PKU.WHXB201602251
%X 分别采用浸渍法、柠檬酸络合法以及沉淀法在SAPO-11分子筛上负载MnOx,制备了一系列MnOx/SAPO-11催化剂。考察了催化剂的低温NH3选择性催化还原(SCR) (NH3-SCR) NOx的性能。结果表明,沉淀法制备的负载量为20%(w)的MnOx/SAPO-11催化剂表现出最优异的低温NH3-SCR性能及N2选择性。通过X射线衍射(XRD)、扫描电镜(SEM)、能量散射谱(EDS)、原子吸收光谱(AAS)、N2吸附-脱附、X射线光电子能谱(XPS)、H2程序升温还原(H2-TPR)、NH3程序升温脱附(NH3-TPD)以及NO/O2程序升温脱附-质谱(NO/O2-TPD-MS)等多种表征手段对催化剂的结构及表面性质进行分析。表征结果显示,采用不同方法制备催化剂时,其表面MnOx的存在形式和晶相结构不同。沉淀法制备的催化剂表面存在无定型态MnOx以及MnO2晶型,具有较大的介孔及外表面积、更多比例的Mn4+和化学吸附氧,同时表面存在对反应有利的中强酸以及强酸。因此,催化剂在低温SCR反应阶段能够生成重要中间产物NO2,从而表现出最佳低温活性。同时,三种制备方法均能使MnOx相对均匀分散在SAPO-11表面。SAPO-11对催化剂表面MnOx物种的形成具有一定的影响,从而影响催化剂的酸性,拓宽了MnOx的活性温度窗口,提高了催化剂的N2选择性。<br>MnOx/SAPO-11 catalysts were prepared by impregnation, citric acid, and precipitation methods for low-temperature selective catalytic reduction (SCR) of NO with NH3. The results indicated that the MnOx/SAPO-11 catalyst with 20%(w) Mn loading prepared by the precipitation method showed the best SCR activity and N2 selectivity. X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), atomic absorption spectrometry (AAS), N2 adsorption-desorption, X-ray photoelectron spectroscopy (XPS), H2 temperature-programmed reduction (H2-TPR), NH3 temperature-programmed desorption (NH3-TPD), NO/O2 temperature-programmed desorption, and mass spectrometry (NO/O2-TPD-MS) were used to analyze the structural properties and catalytic performance of the catalysts. The results indicated that different manganese oxides were formed on the surface of SAPO-11 by the three different preparation methods. MnOx loaded via the precipitation method existed as MnO2 phase and amorphous MnOx. The advantages of the catalyst prepared via this method were a large mesoporous and external surface area, the highest content of chemisorbed oxygen and Mn4+ as well as more favorable medium and strong acid sites. Thus, more NO2 was produced on the catalyst during low-temperature SCR, which was a primary goal. MnOx prepared by all three methods could be well-dispersed on the surface of SAPO-11. The dispersive action of SAPO-11 could affect the formation of MnOx, which could affect the acidity of the catalysts. Thus, the temperature window was widened and N2 selectivity was improved compared with pure MnOx, with SAPO-11 acting as an excellent carrier
%U http://www.whxb.pku.edu.cn/CN/Y2016/V32/I5/1236