【作者】 夏莹；

【导师】 黄学辉；

【作者基本信息】 武汉理工大学 ， 材料学， 2010， 硕士

【摘要】 钙钛矿型复合氧化物是一种应用领域非常广泛的功能型材料,尤其是具有优良的催化性能,作为最有希望取代贵金属的环保催化材料已受到国内外许多研究者的关注,如何提高钙钛矿型复合氧化物的催化活性及其抗老化性能是目前研究的热点之一。在对文献调研和分析钙钛矿型复合氧化物催化剂研究现状及进展的基础上选择稀土钙钛矿型复合氧化物作为研究对象,研究材料制备及其性能,为汽车尾气催化转化器材料提供理论与实验数据。本文采用柠檬酸溶胶-凝胶自燃法制备钙钛矿型复合氧化物La-Ba-Cu基催化剂,在A位掺杂Sr、Ca、Mg、K,在B位掺杂Co、Fe、Cr、Mn等多种金属元素,实施对催化剂的改性。采用XRD、SEM、BET、TPD等手段对制备的催化剂进行相关表征,研究不同位置、不同金属元素的掺杂对催化剂结构、微观形貌和性能的影响,通过测试催化剂对CO、CH4、NO气体的催化转化效率,评价催化剂的活性大小,探索掺杂对催化剂活性的影响。同时,对制备的新鲜催化剂进行了热老化和硫老化实验,考察掺杂对催化剂抗老化性能的影响。由XRD分析表明,在本实验条件下,B位Co、Fe单掺杂以及B位Fe、Co双掺杂和采用K、Co的A、B位复合掺杂样品能形成纯度较高的钙钛矿结构,A位掺杂的样品多数都有杂质相La2Cu04生成。从样品的微观形貌上可以观察到,掺杂后的样品颗粒尺寸减小,分散均匀,团聚较少。其中较为突出的是La4BaCu4CoO13+δ和La4Ba0.5K0.5Cu3Co2O13+δ,颗粒大小在50-100nm左右。同时,BET结果也印证了其具有较大的比表面积。样品的O2-TPD测试结果表明,B位掺杂Co、Fe以及K、Co的复合掺杂使催化剂的表面吸附氧增多。催化活性的测试表明催化剂的活性与表面吸附氧浓度有密切关系,其中活性最好的是La4Ba0.5K0.5Cu3Co2-O13+δ,其对CH4、CO、NO起燃温度T50分别为250℃、265℃、280℃。催化剂经900℃热老化8h后,催化剂的颗粒都有所长大,比表面积减小,其中La4BaCu4CoO13+δ降低较少,老化后表面积为4.967m2/g。其抗老化性能较好。硫老化后,A位掺杂样品La4Ba0.5Sr0.2Cu5O13+δ的结构保持最好,没有发生结构解体,而La4BaCu4CoO13+δ和La4BaCu4Fe0.5Co0.5O13+δ都有不同程度的结构解体,生成了对应的金属硫酸盐。更多还原

【Abstract】 Perovskite-type composite oxide is a funtional materials which are widely used, especially the excellent catalytic properties. They have attracted particularly attentions because of their special applications as the most promising to replace precious metals catalysts materials, how to improve the catalytic activity of perovskite-type composite oxide is an important aspect of the study. In this paper we choose perovskte-type oxides as disquisitive object, researched their preparation and properties, and provided academic and experimental data for catalytic instrument of automobile’s exhaust.In this paper, a series of layered perovskite-type La-Ba-Cu-based catalyst were synthesized by citrate acid sol-gel method. Doping Sr, Ca, Mg, K in the position of "A", and doping Co, Fe, Cr, Mn in the position of "B" to improve their related properties. The physical and chemical properties and function mechanism of different doping catalysts were characterized by means of XRD, SEM, BET, TPD, the influence of doping on catalytic properties were researched. The catalytic activities were evaluated by testing the conversion efficiency of CO, CH4, and NO gas. Meanwhile, thermal aging and sulfur aging experiments were taken on fresh catalysts, the anti-sulfuration and anti-aging properties on doping catalysts were studied.The XRD spectrum demonstrated that catalysts which single-doped Fe, Co and double doping Fe, Co in the position of "B" and composite doping K, Co in the position of "A","B" were formed a high purity perovskite-type structure at 750℃, but samples which single-doped in the position of "A" almost have a impurity phase La2CuO4. From the microstructure of catalysts, we can be observed that particle size of the doped samples decreased, and evenly dispersed, less conglobation. The more prominent is the La4BaCu4CoO13+δand La4Ba0.5K0.5Cu3Co2O13+δ, their particle size is about 50-100nm. Meanwhile, BET results also confirmed that they had a smaller surface area. The O2-TPD demonstrated that the surface adsorbed oxygen increased on the catalysts which doping Co, Fe in the position of "B" and composite doping K, Co. Catalytic activity tests demonstrated that the catalytic activity is closely related with the concentration of surface adsorbed oxygen, which had the highest activity is La4Ba0.5K0.5Cu3Co2O13+δ, their light-off temperature T50 of CH4, CO, NO were 250℃,265℃,280℃.After thermal aging at 900℃for 8h, the catalysts particles and surface area had an obviously decrease, in which, after aging the La4BaCu4CoO13+δhad largest surface area which was 4.967m2/g, and had better anti-aging properties. After sulfuration, the structure of La4Ba0.8Sr0.2Cu5O13+δremained steady, haven’t occurred structural disaggregation, but La4BaCu4CoO13+δand La4BaCu4Fe0.5Co0.5O13+δhave different degree of structural disaggregation, formatted the corresponding metal sulfate.更多还原