CeWO_(x)催化剂协同脱除氮氧化物及氯代芳香化合物的反应机制研究  

Reaction mechanism study for synergistic elimination of NO_(x) and chloroaromatics on CeWO_(x) catalysts

作　　者：于宇雷 翁小乐[1,2] 吴忠标 YU Yulei;WENG Xiaole;WU Zhongbiao(College of Environmental and Resource Sciences,Zhejiang University,Hangzhou 310058;Zhejiang Provincial Engineering Research Center of Industrial Boiler&Furnace Flue Gas Pollution Control,Hangzhou 310058)

机构地区：[1]浙江大学,环境与资源学院,杭州310058 [2]浙江省工业锅炉炉窑烟气污染控制工程技术研究中心,杭州310058

出　　处：《环境科学学报》2022年第2期351-365,共15页Acta Scientiae Circumstantiae

基　　金：国家自然科学优秀青年基金(No.21922607);浙江省自然科学杰出青年基金(No.LR19E080004)。

摘　　要：多污染物协同控制是大气污染控制技术的发展方向.本文以氮氧化物(NO_(x))及氯苯(CB)为典型多污染物组分,考察了不同Ce/W比例CeWO_(x)催化剂协同脱除NO_(x)及CB的催化性能及反应特征.其中,Ce_(8)W_(1)O_(x)催化剂表现出最佳的催化活性,在温度为350℃时,NO_(x)、CB转化率均达到100%.NO_(x)选择性催化还原(SCR)、CB催化氧化(CBCO)和协同脱除反应(SCR+CBCO)的对比实验发现,协同反应的NO_(x)和CB转化均受到不同程度的抑制,尤以SCR对CBCO的抑制作用更为明显.TPSR及DRIFT表征证明NH_(3)和CB之间的竞争性吸附是SCR和CBCO协同反应活性下降的主要原因.CeWO_(x)催化剂上CB解离生成的氯经氧空位活化形成Cl·,易导致亲电加氯反应从而促进多氯苯生成.SCR为CBCO提供了额外氢,源于NH_(3)吸附于Lewis酸位点并被氧空位上活性氧物种攻击脱氢生成酰胺物种(NH_(2)^(-)/NH^(-))的反应过程,该氢源促使Cl·/Cl^(-)以HCl形式从催化剂表面脱离.苯甲腈等含氮副产物的存在表明SCR及CBCO协同反应的中间产物发生了多污染物耦合.The synergistic elimination of multi-pollutant represent the developing direction of air pollution control technology.In this paper,the synergistic elimination of nitrogen oxides(NO_(x))and chlorobenzene(CB),as typical composite pollutants,on CeWO_(x)catalysts with different Ce/W ratios was studied.Ce_(8)W_(1)O_(x)exhibited the best catalytic activity,which achieved both NO_(x)and CB conversion rate of 100%at 350℃.The comparative experiments of selective catalytic reduction(SCR)of NO_(x),CB catalytic oxidation(CBCO)and synergistic reaction(SCR+CBCO)indicated that NO_(x)and CB conversation were inhibited in different degrees,where CBCO reaction was inhibited more obviously by SCR.The results of TPSR and DRIFT characterizations showed that competitive adsorption between NH_(3) and CB contributed the most to their deactivations.Chlorine dissociated from CB on Ce_(8)W_(1)O_(x)catalyst formed Cl·at oxygen vacancy,which facilitated the polychlorobenzene formation via an electrophilic chlorination reaction.SCR provided additional hydrogen for CBCO due to the reaction process of NH3 adsorbed to Lewis-acid site and dehydrogenated to form amide species(NH_(2)^(-)/NH^(-))as attacked by reactive oxygen species on oxygen vacancies,which promoted the separation of Cl·/Cl^(-) in the form of HCl from the catalyst surface.The detection of nitrogen-containing byproducts such as benzonitrile showed that multi-pollutant coupling occurred between the intermediate products of SCR and CBCO reactions.

关 键 词：氮氧化物 氯苯 CeWO_(x)催化剂 协同脱除 竞争性吸附 多污染物耦合 

分 类 号：X511[环境科学与工程—环境工程]