作　　者： (马杰文）; (黄碧纯）; (喻成龙）;

机构地区： 华南理工大学环境与能源学院,广州510006

出　　处： 《环境科学学报》 2017年第9期3297-3305,共9页

摘　　要： 采用尿素沉淀法制备了一系列Fe_2O_3/SAPO-34催化剂,考察了催化剂焙烧温度(200、300、400、500℃)对低温NH_3选择性催化还原(NH_3-SCR)NO性能的影响,并利用X射线衍射(XRD)、N_2吸附-脱附、原子吸收光谱(AAS)、场发射扫描电镜(FE-SEM)、X射线光电子能谱(XPS)、H_2程序升温还原(H_2-TPR)、NH_3程序升温脱附(NH_3-TPD)等多种手段对催化剂的表面结构和物理化学性质进行表征分析.XRD和FE-SEM分析表明,在较低的焙烧温度(<400℃)下,铁物种能够高度均匀地负载在SAPO-34表面上.NH_3-TPD和H_2-TPR分析表明,高分散状态的Fe_2O_3使催化剂暴露出更多的强酸位和活性位,有利于提高催化剂的NH_3吸附和活化能力及氧化还原性能,从而使催化剂呈现出更高的低温SCR活性.BET和XPS分析表明,在较低的焙烧温度下,Fe_2O_3/SAPO-34催化剂具有更大的比表面积和更高的化学吸附氧比例,促进NO氧化为中间产物NO_2,从而加快低温SCR反应的进行.活性测试结果表明,300℃焙烧的Fe_2O_3/SAPO-34催化剂具有最佳的低温活性和较强的抗硫抗水性能,在空速为40000 h^(-1)的条件下,且反应温度为190~240℃时,NO转化率达90%以上且N_2选择性接近100%. A series of FeaO3 supported on SAPO-34 catalysts for the selective catalytic reduction of NO with NHs were prepared by an improved urea- precipitation method and calcined at different temperatures （ 200, 300, 400 and 500℃ ）. The structural and physicochemical properties of the obtained catalysts were investigated by X-ray diffraction （ XRD）, N2 adsorption-desorption isotherms, atomic absorption spectrometry （ AAS）, field emission scanning electron microscopy （FE-SEM）, X-ray photoelectron spectroscopy （XPS）, Ha-temperature programmed reduction （H2-TPR）, and NHs- temperature programmed desorption （NHs-TPD）. The XRD and FE-SEM results confirmed that the iron species of catalysts calcined at relatively low temperature （ 〈400℃ ） were highly dispersed on the surface of the SAPO-34. The NH3-TPD and H2-TPR results suggested that the highly dispersed ferric oxides were favorable for exposing more strong acid sites or active sites and thus improving the Nil3 adsorption capability and oxidation-reduction ability of catalysts, resulting in higher catalytic activity. The BET and XPS results indicated that the catalysts calcined at lower temperature possessed larger specific surface area and higher content of chemisorbed oxygen species, which were helpful for NO oxidation to NO2 and then accelerated the low- temperature SCR reaction. The catalytic activity test demonstrated that the Fe2 O3/SAPO-34 catalysts calcined at 300℃ exhibited more than 90% NO conversion and almost 100% N2 selectivity at 190-240℃ at a high space velocity of 40000 h-1 , and the strong resistance to SO2 and H2O.

关 键 词： 选择性催化还原 氮氧化物 铁氧化物 分子筛 焙烧温度