V_2O_5/TiO_2与MoO_3/TiO_2催化剂表面结构形貌及其对催化氧化碳烟活性的影响  

Surface Structure and Appearance of V_2O_5/TiO_2 and MoO_3/TiO_2 Catalysts and Their Effect on Oxidation of Soot

作　　者：梅丛蔚 李立昌[1] 梅德清[1] 赵晓东[1] 袁银男[2] 

机构地区：[1]江苏大学汽车与交通工程学院,江苏镇江212013 [2]苏州大学能源学院,江苏苏州215006

出　　处：《环境科学研究》2016年第11期1665-1671,共7页Research of Environmental Sciences

基　　金：国家自然科学基金项目(51376095;51506101);江苏高校优势学科建设工程资助项目(苏政发办[2014]72号)

摘　　要：为研究纳米级V_2O_5与MoO_3催化剂表面结构对其催化氧化碳烟活性的影响,以TiO_2为载体,采用等体积浸渍法制备了不同负载率(5%、10%、20%、40%)的V_2O_5/TiO_2与MoO_3/TiO_2催化剂,通过扫描电镜(SEM)、X射线衍射仪(XRD)对比研究了2种催化剂在TiO_2载体上的分散状态及物相结构.以Printex-U碳黑为试验用碳烟,采用热重分析仪对V_2O_5与MoO_3催化剂催化碳烟氧化的活性进行了比较.结果表明:V_2O_5与MoO_3在TiO_2载体上均存在一个单层分散饱和阈值,分别为V20(负载率为20%,下同)、Mo10,在该阈值前后活性组分在载体上分别以单层分散状态和明显的晶态存在.对于V_2O_5催化剂,其最佳催化活性出现在负载率接近单层分散饱和阈值时,与无催化状态相比,Ti(起燃温度)、Tp(最大失重率温度)以及Tf(燃尽温度)分别下降了69.1、46.0、23.0℃,有明显的阈值效应.而对于MoO_3催化剂,因其自身低熔点性而表现出良好的表面迁移能力,再加上α-MoO_3晶体特有的层状结构,使其可释放出更多的晶格氧,随着负载率的增加,该催化剂催化氧化碳烟活性持续增加,并且未观察到明显的阈值效应.研究显示,在相同负载率下,MoO_3催化剂催化氧化碳烟活性均高于V_2O_5催化剂.The effects of surface structure and appearance of active species on nano-scale V2O5/TiO2 and MoO3/TiO2 catalysts＇ catalytic performances for diesel soot catalytic oxidation were investigated. The search provided a theoretical basis for development of novel catalysts, enhancement of the soot catalytic oxidation efficiency and reduction of PM emissions. The catalysts with different loading rates （5% , 10% , 20% , 40% ） were prepared by an impregnation method, and the dispersing phase and physical-chemical attributes of active species loaded on TiO2 were characterized using Scanning Electron Microscope （SEM） and X-Ray diffraction （XRD）. Printex-U carbon black was utilized to replace the practical engine soot. The catalytic oxidation activity over soot was evaluated using a TG/DTA analyzer, and was evaluated by the ignition temperatures （Ti）, the weight loss peak temperatures （Tp） and the burnout temperatures （Tf）. The results showed that there was a monolayer dispersion threshold, which was V20 and Mo10 for V2O5 and MoO3 catalysts separately, when 69.1, 46.0 and 23.0 ℃ respectively. However, as for the MoO3 catalysts, the characteristic temperatures decreased with increased loading rate, which implies that the catalytic activity was enhanced. This is because the favorable surface migration of active species resulted from lower melting point and more lattice oxygen provided by the α-MoO3 crystal of the layer structure. Therefore, no threshold effect was perceivable for the MoO3/TiO2 catalyst. Moreover, with the same loading rate, the MoO3 catalysts normally present higher aeti,lities than the V2O5 catalysts.

关 键 词：V2O5 MOO3 催化剂 阈值效应 活性 碳烟 

分 类 号：X705[环境科学与工程—环境工程]