V_2O_5-CeO_2/TiO_2-ZrO_2催化剂表征及NH_3还原NO_x性能（英文）  

Characterization and activity of V_2O_5-CeO_2/TiO_2-ZrO_2 catalysts for NH_3-selective catalytic reduction of NO_x

作　　者：张亚平[1] 郭婉秋[1] 王龙飞[1] 宋敏[1] 杨林军[1] 沈凯[1] 徐海涛[1] 周长城[1] 

机构地区：[1]东南大学能源与环境学院能源热转换及其过程测控教育部重点实验室,江苏南京210096

出　　处：《催化学报》2015年第10期1701-1710,共10页

基　　金：supported by the Natural Science Foundation of Jiangsu Province(BK2012347);the National Natural Science Foundation of China(51306034);the National Basic Research Program of China(973 Program,2013CB228505)~~

摘　　要：商业选择性催化还原(SCR)催化剂V2O5-WO3(Mo O3)/TiO2存在反应温度窗口窄(300–400 oC)和SO3转化率高等缺点,同时占催化剂总质量80%以上的载体TiO2比表面积小,热稳定性差.已有研究发现TiO2-ZrO2固溶体具有较大的比表面积和较强的表面酸性,TiO2与ZrO2的摩尔比为1:1时其比表面积达到最大.CeO2作为SCR催化剂的组成部分,由于其优良的储氧和放氧能力受到广泛关注.研究表明,CeO2-CuO,Ce/Ti-Si-Al和Mo2O3(Co2O3)/Ce-Zr等催化剂具有优良的SCR脱硝活性,同时对V2O5-WO3/TiO2催化剂进行CeO2改性,可提高催化剂的抗SO2中毒能力.实际烟气组分中同时存在SO2和H2O,必定会导致催化剂硫酸盐中毒,而目前对含Ce催化剂的硫酸盐中毒情况研究较少,因此开发新型高效脱硝催化剂十分必要.前期我们研究了xCeO2-3%V2O5/TiO2-ZrO2催化剂,发现CeO2可以显著拓宽脱硝温度窗口,同时增强催化剂酸性位点,但是V2O5含量较高时对环境及人体健康均有较大危害.本文采用共沉淀法制备摩尔比为1:1的TiO2-ZrO2固溶体,用浸渍法负载不同摩尔比的CeO2和1%的V2O5,得到一系列V-xCe/Ti-Zr催化剂,结合X射线衍射(XRD)、比表面积测试(BET)、高分辨透射电镜(HRTEM)、程序升温还原(H2-TPR)、原位漫反射红外光谱(in situ DRIFTS)和程序升温脱附(NH3-TPD)等手段分析催化剂的晶相、活性物质分散程度、氧化还原性质及表面酸性,在200–450 oC范围内考察Ce掺杂催化剂选择性催化还原NOx的脱硝活性,并在250oC测试催化剂在NH3+NO+O2+SO2+H2O气氛中的脱硝活性,研究催化剂抗硫酸盐中毒能力.研究发现,CeO2掺杂可以拓宽脱硝反应活性窗口,V-0.2Ce/Ti-Zr(摩尔比Ce:Ti=0.2)表现出最优的脱硝性能,在250–350 oC范围内脱硝效率均在92%以上,同时与前期研究结果对比发现CeO2含量较高时会导致高温段NOx转化率下降.XRD和HRTEM结果表明,ZrO2的添加可以显著降低载体TiO2的结晶度,复合氧化物TiO2-ZrA series of V2O5-xCeO2/TiO2-ZrO2 （Ti-Zr） catalysts with different CeO2 loadings （x= molar ratio of Ce/Ti-Zr） were prepared, and their catalytic performance for the selective catalytic reduction （SCR） of NOx by NH3 was investigated in the presence of SO2 and H2O. The physicochemical properties of the catalysts were characterized by N2 sorption analysis, high-resolution transmission electron microscopy, X-ray diffraction, H2-temperature-programmed reduction, NH3-temperature-pro-grammed desorption, and in situ diffuse reflectance infrared Fourier transform spectroscopy. The presence of CeO2 in the catalysts led to higher conversion of NOx within a wider operating tempera-ture range. V2O5-xCeO2/Ti-Zr catalyst （x= 0.2） exhibited the highest activity. Higher loadings of CeO2 adversely affected the NOx conversion at higher temperatures. The characterization results revealed that CeO2 was amorphous and highly dispersed over the Ti-Zr support. The catalysts featured sin-gle-crystal electron diffraction features. The presence of CeO2 significantly increased the reduction ability of the catalysts, and low V2O5 loadings were beneficial to the low-temperature SCR. V2O5/TiO2 catalyst exhibited medium-to-strong and strong acid desorption of NH3, whereas V2O5/Ti-Zr fea-tured weak acid sites onto which desorption of NH3 occurred. The presence of CeO2 could increase the amount of both the Br-nsted and Lewis acid sites, which were expected to play a key role in the excellent SCR activity. In contrast, the presence of V2O5 reduced the amount of Br-nsted acid sites. All V2O5-CeO2/Ti-Zr catalysts exhibited poor stability and weak resistance to H2O poisoning but high resistance to SO2. However, the original catalytic activity of V2O5-xCeO2/Ti-Zr （x = 0.3） could be fully restored following poisoning with SO2and H2O. For the poisoned catalysts, the formation of Ce（SO4）2 led to the decreased catalytic performance at the intermediate temperatures, which increased at the higher temperatures because of the presence of

关 键 词：二氧化铈 钛-锆 酸性位 氮氧化物 选择性催化还原 中毒 

分 类 号：O643.36[理学—物理化学]