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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 Fe 2 O 3 / SAPO-34 catalysts were prepared by urea precipitation method. The effects of catalyst calcination temperature (200, 300, 400 and 500 ℃) on the performance of low temperature NH 3 -catalyzed reduction (NH 3 SCR) Ray diffraction (XRD), N 2 adsorption-desorption, atomic absorption spectroscopy (AAS), field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), H 2 temperature-programmed reduction The structure and physico-chemical properties of the catalyst were characterized by various means such as temperature-programmed desorption (NH 3 -TPD), and XRD and FE-SEM analysis showed that the iron species can be highly calcined at lower calcination temperatures (<400 ℃) The results of NH 3 -TPD and H 2 -TPR showed that the highly dispersed Fe 2 O 3 catalyst exposed more strong acid sites and active sites, which was beneficial to improve the adsorption and activation ability of NH 3 and oxidation of the catalyst Reduction performance, so that the catalyst showed higher low temperature SCR activity.BET and XPS analysis showed that the lower the calcination temperature, the Fe 2 O 3 / SAPO-34 catalyst has a larger specific surface area and higher chemisorption oxygen ratio, Promote NO oxidation to intermediate NO 2, thereby accelerating Temperature SCR reaction.The results of the activity test showed that the Fe_2O_3 / SAPO-34 catalyst calcined at 300 ℃ has the best low temperature activity and the strong anti-sulfur and water-resistance. Under the conditions of airspeed of 40000 h ~ (-1) , And the reaction temperature is 190 ~ 240 ℃, NO conversion rate of more than 90% and N2 selectivity close to 100%.