【作者】 辛绍强；

【导师】 范国梁；

【作者基本信息】 天津大学 ， 材料学， 2007， 硕士

【摘要】 柴油机主要排放物氮氧化物和微粒是大气污染的主要来源之一严重危及人类的健康。通过目前柴油机排放处理技术难以满足日趋严格的排放标准。必须开发新的柴油机排气后处理技术以进一步降低柴油机氮氧化物和微粒排放。本文对La_1-xA)xCo_1-yByO₃复合钙钛矿催化剂对于柴油机尾气排放物净化效果进行了相关研究,主要研究内容如下:1.采用低温燃烧法合成了La_1-xK_xCo_1-yFeyO₃系钙钛矿型复合氧化物催化剂,此种方法制备的催化剂颗粒分散均匀,平均粒子半径为90～200nm,比表面积约为9～15 m²/g。利用XRD、SEM、TEM、BET等方法对催化剂的晶体结构、物相特征、表面结构及其元素价态等理化性能进行了表征。采用程序升温技术对所制得的催化剂对于NO_x的净化效果以及在空气条件下对于PM的净化效果进行了相关实验,结果表明,对于NO_x的去除,La_0.7K_0.3CoO₃的催化效果最好。而对于PM的去除,La_0.6K_0.4CoO₃最为有效,使PM的起燃温度降低到400℃左右。2.分别选取A位部分取代的La_1-xK_xCoO₃（x=0.1、0.2、0.3、0.4、0.5）B位部分取代的LaFe_yCo_1-yO₃ （ y=0.1、0.2、0.3、0.4、0.5、0.6、0.7 ）和La_1-xK_xFe_yCo_1-yO₃（x=0.2、0.3、0.4,y=0.5、0.6）钙钛矿复合型氧化物,与碳黑按10:1比例混合、研磨使之紧密接触。利用热重—红外联用分析系统,以模拟气体代替实际气体来研究适合用于催化型颗粒物捕集器的催化剂。根据实验结果得出当K、Fe同时部分取代La和Co的LaCoO₃系钙钛矿型复合氧化物催化剂时,K的取代量等于0.2时(La_0.8K_0.2Fe_0.5Co_0.5O₃)PM起燃温度最低,当K的取代量一定时Fe的取代量越少则PM起燃温度越低。另外碳颗粒在NO₂中的起燃温度远远低于其在空气气氛中的起燃温度,证明NO₂浓度的升高有利于碳颗粒的燃烧,即在尾气处理过程中NO₂对颗粒物去除起着重要作用。在催化燃烧的过程中,不仅NO₂能与颗粒物反应,同时NO也能与颗粒物反应从而加速颗粒物的去除,验证了实验中所制得的催化剂具有颗粒物与NO_x协同去除作用,由于NO_x具有去除颗粒物的作用,而低温等离子体作用时能够产生大量的NO_x于是间接证明了低温等离子体可以用于柴油机尾气中颗粒物的净化,从而为低温等离子体再生催化型颗粒捕集器净化柴油机尾气排放的实际应用奠定了理论基础和实践指导。更多还原

【Abstract】 The particulate matter （PM） and nitrogen oxides （NO_x） emissions from diesel exhaust are two of main pollutants damaging environment and human health. With stringenter and stringenter emission regulations, the diesel automotive industry is currently facing serious challenges to meet the specific regulations concerning both PM and NO_x. However, the future emissions targets cannot be reached by the combu- stion adjustment and the current after-treatment technologies. Therefore, new methods for simultaneous removal of PM and NO_x from rich oxygen diesel exhaust are needed. The investigation on the purification of diesel emission by the catalytic technology was carried out in this paper.Firstly, a series of La_1-xK_xCo_1-yFeyO₃ catalysts of perovskite type structure had been synthesized at low temperature through a combustion process, during which the catalysts with particle diameters that scatters in the domain of 90 and 200 nm was prepared , and the BET values of the catalysts range from 9 to 15 m2/g. The crystal structure, phase character, surface texture and valence were characterized by XRD, SEM, and TEM. These catalysts were investigated in removal of NO_x, and PM from diesel exhaust gases using temperature-programmed reaction. The results show that La_0.7K_0.3CoO₃ behaved high catalytic activity in NO_x abatement. However initiated temperature of PM dropped to 400℃under the catalytic effect of La_0.6K_0.4CoO₃.Secondly, perovskite catalysts available for catalytic diesel particulate filter was selected by thermal gravimetric—infrared ray with model gas in place of real diesel exhausts. This experiment was carried out with a 10:1 by weight mixture of soot and powder catalysts including La_1-xK_xCoO₃（x=0.1、0.2、0.3、0.4、0.5）,. LaFe_yCo_1-yO₃（y=0.1、0.2、0.3、0.4、0.5、0.6、0.7）and La_1-xK_xFe_yCo_1-yO₃ （x=0.2、0.3、0.4,y=0.5、0.6）. The results indicate that La0.8 K0.2 Fe 0.5Co0.5O3 have the highest activity for initiated temperature of PM, and the temperature decreased with increasing y value in La_1-xK_xFe_yCo_1-yO₃. In addition, NO_x extremely contribute to soot combustion compared with air, which implies that NO₂ plays an important role in PM removal in the process of diesel exhausts cleaning. NO also accelerates PM combustion. Because non-thermal plasma produce lots of NO_x, it is reasonable for using NTP in removal of PM in diesel exhausts.更多还原