【作者】 马涛；

【导师】 王睿；

【作者基本信息】 山东大学 ， 环境工程， 2008， 硕士

【摘要】 随着人类社会的不断发展,钢铁冶炼、火力发电、汽车尾气及城市垃圾的焚烧等都会产生越来越多对生态环境和人类健康都非常有害的气体,如SO₂,NO_x,CO等。近年来,世界各国的科研单位、工业生产部门纷纷开始进行废气污染治理方法的研究和应用。氮氧化物（NO_x）是较难治理又危害极大的气态污染物,是当前环保研究的热点之一。氮氧化物的直接催化分解是公认的消除NO_x污染最有吸引力的方法之一,催化分解法具有不产生二次污染、不消耗还原剂、经济性好、工艺简单等优点而受到人们的广泛关注。近年来,杂多酸（HPA）及其相关化合物（HPC）作为一种新颖的NO_x分解催化剂吸引了各国学者的关注。HPC作为一种环境友好的催化新材料已在有机合成工业催化领域得到成功应用,然而迄今尚无HPC在NO_x催化转化方面的工业应用先例。本文系统地考察了多种固体杂多酸（盐）与多种载体的组合,筛选构建了具有吸附-分解NO_x功能的多酸催化新体系。自行设计了固定床NO_x吸附-分解催化性能评价系统,测试了制得的17种固体杂多化合物和8个系列的多种负载型多酸催化体系（主要是负载型磷钨酸,8种载体）的性能,借助现代仪器分析手段对几种性能优异的多酸催化新体系进行了红外光谱、X射线衍射、透射电镜和比表面积的表征。研究发现,磷钨酸、硅钨酸和磷钼酸铵都可以成为构建多酸催化新体系的候选催化剂,分别有66.3%,62.9%和69.5%的NO_x吸附率,杂多酸铵盐对NO_x具有催化还原作用。筛选得到SnO₂,ZSM-5分子筛,USY沸石和SiO₂可以作为构建多酸催化新体系的高性能载体,它们的最佳HPW负载量分别为50%,50%,16.7%和28.6%,它们负载HPW之后得到的最佳NO_x吸附效率分别是77.3%,70.5%,65.7%,62.3%。性能最佳的催化体系为50%负载量的HPW/SnO₂。对最佳催化体系HPW/SnO₂（50%）进行了吸附过程特性试验,考察了烟气湿度、氧含量、床层温度、空速和进气浓度对其脱硝性能的影响。对HPW和HPW/SnO₂（50%）进行了NO_x吸附容量的测定,得到了它们的饱和吸附曲线和累积吸附量曲线,并通过积分计算出了它们的饱和吸附量分别为50.5 mg NO₂/gHPW和85.4 mg NO₂/gHPW。利用红外光谱表征结合文献资料分析了多酸催化系的NO_x吸附机理,认为吸附过程是假液相行为下的体相Ⅰ型扩散吸附,且杂多酸的B酸酸性越强,脱硝性能越好,综合分析后认为NO_x是通过与体相质子结合形成（NOH）⁺而吸附进入体相的吸附机理。对HPW和HPW/SnO₂（50%）进行了程序升温脱附试验,采用GC-MS检测分解产物,发现有N₂生成,从而确认采用本研究工作筛选得到的NO_x吸附-分解多酸催化新体系无需还原剂即可实现气态污染物中NO_x向N₂的转化。更多还原

【Abstract】 With the development of modern society, many proceses, such as steel making, electric power generation, the operation of car engines and incineration of municipal refuse are emitting more and more gases, such as SO₂, NO_x, CO, et al, which are harmful to ecological environment and human health. In recent years, both academia and industry all over the world have paid deep concern on the problem of air pollution. The removal of nitrogen oxides （NO_x） is one of the hottest points in the area of enrionmental pollution treatment because NO_x are very harmful and hard to be removed.Direct catalytic decomposition of NO_x has been recognized as one of the most attractive methods for eliminating pollution derived from NO_x, since it does not require addition of any reducing agent and the only products are N₂ and O₂. This method, simple and cheap, would avoid a secondary pollution. Heteropoly acids （HPAs） or heteropoly compounds （HPCs）, as a new type of catalyst for NO_x direct decomposition, have attracted the attention of worldwide researchers during the past years. HPCs are environment-friendly caltalysts and have been applied successfully in organic synthesis, but there has been no report on the industrial application of the NO_x catalytic decomposition by HPCs, to date.Seventeen kinds of solid-state heteropoly acids or their salts and eight kinds of supported heteropoly acids （mostly HPW with eight kinds of supports） with different loadings were prepared and evaluated in this study. All the catalyst systems were evaluated using a fixed-bed catalytic reactor. The adsorption efficiencies of H₃PW₁₂O₄₀ （HPW）, H₄SiW₁₂O₄₀ and （NH₄）₃PMo₁₂O₄₀ can reach upto 66.3%, 62.9% and 69.5%, respectively. HPW/SnO₂, HPW/ZSM-5, HPW/USY and HPW/SiO₂ were selected as efficient catalyst systems, with NO_x adsorption efficiencies being 77.3%, 70.5%, 65.7 and 62.3%. respectively, corresponding to the HPW loadings of 50%, 50%, 16.7% and 28.6% These four catalysis systems are characterized by IR, XRD, TEM and BET. Taking HPW/SnO₂ （50% loading） as an example, the process characteristics were carried out. Factors such as gas humidity, oxygen content, adsorption temperature, space velocity and initial NO_x concentration, were studied. NO_x saturated adsorption curve and accumulated quantity curve for HPW and HPW/SnO₂ （50% loading） were gained. The saturated amounts of NO_x adsorbed were equal to 50.5 mg NO₂/g-HPW for H₃PW₁₂O₄₀ and 85.4 mg NO₂ /g-HPW for HPW/SnO₂ （50% loading）. It was showed that there was an obvious synergetic effect between HPW and supports. Based on IR study and literatures, the NO_x adsorption mechanism involving the combination of NO_x with bulk proton to form （NOH）⁺ which can be incorporated into the secondary structure of HPCs was discussed. It is concluded that the process of NO_x adsorption on HPCs is the bulk diffusion of NO_x into HPCs by "pseudoliquid phase" effect and the interaction between NO_x and HPCs depends on the Br（?）nsted acidic strength of the solid-state HPCs. With the aid of GC-MS analysis, the process effectiveness for NO_x conversion to N₂ was confirmed by the temperature programmed desorption experiments for HPW and HPW/SnO₂ （50% loading）.更多还原