【作者】 吴韶亮；

【导师】 刘欣梅； 阎子峰；

【作者基本信息】 中国石油大学 ， 工业催化， 2007， 硕士

【摘要】 随着汽车尾气污染的日益严重,尾气净化成为时势所趋。本论文的主要目的就是合成具有大比表面积、较好热稳定性和储氧性能的铈锆固溶体,并以其为载体制备汽车尾气净化催化剂,为新型汽车尾气净化催化剂的开发奠定基础。分别采用固相反应法、共沉淀法和水热晶化法合成了铈锆固溶体,并考察了各因素对固溶体结构和性能的影响。结果表明,固相反应法铈锆固溶体表面缺陷多、稳定性差,焙烧后孔结构坍塌、比表面积较小、孔径分布较宽;而水热晶化法铈锆固溶体表面缺陷少、结构稳定性高、比表面积大、孔径分布单一;与表面缺陷相对应,固相反应铈锆固溶体具有较大的储氧量和较低的还原温度,而水热晶化铈锆固溶体具有相对较低的储氧量和较高的还原温度;共沉淀法固溶体介于两者之间。在对合成条件的优化过程中发现,Taguchi设计法是一种优化功能材料结构设计方案的有效方法,由此可以方便地获得材料设计过程中的主导因素和最佳的设计条件。通过向固溶体结构中引入过渡金属元素可以有效地改善其热稳定性,其中Pr是最佳的结构稳定剂。采用浸渍法制得铈锆固溶体负载的Pd基尾气净化催化剂,发现以共沉淀法合成的固溶体为载体制得的催化剂有着较低的起燃温度,而水热晶化法的有着最高的转化率,固相反应法的反应性能最差。对于CO转化,催化剂的起燃温度随着Pd负载量的增大而升高,而对于CH4却呈现出相反的规律。关联固溶体结构和性能之间的关系,发现具有较大比表面积、均一孔径分布的固溶体显示了较高的催化反应性能。更多还原

【Abstract】 It is essential to innovate the catalyst for purification of vehicle exhaust gas because air pollution is even serious with increase of vehicles. In this paper, ceria-zirconia solid solution with larger specific surface area, well thermal stability and oxygen storage capacity were prepared to act as support for such purifying catalysts. This work will be benefit to develop a novel catalyst for exhaust gas treatment.Ceria-zirconia solid solution was respectively synthesized via solid state reaction, coprecipitation and hydrothermal methods. The effect of different factors on the structure and performance of solid solution was systematically investigated. The results showed that ceria-zirconia solid solution synthesized by solid state reaction exhibited more surface defective sites and lower stability. It resulted in the lower surface area and wider pore diameter distribution after cacination. While the samples prepared by hydrothermal method bear higher thermal stability, lager surface area and narrow pore diameter distribution. The more surface defective sites contribute the better oxygen storage capacity. It means that the solid solution prepared by solid state reaction possesses the optimum oxygen storage capacity among the three preparation methods, and simultaneously bear the lowest reduction temperature. On the contrary, the samples synthesized by hydrothermal method showed poor oxygen storage capacity and higher reduced temperature. The performance of the ceria-zirconia solid solution synthesized by coprecipitation was in the middle of the others. The research showed that Taguchi design was reasonable method to investigate optimal synthesis conditions. The main effect factor was also obtained using this design method. In order to improve the thermal stability of ceria-zirconia solid solution, transitional metal oxides was introduced. Pr was good stabilizer to improve the structure of solid solution.The catalysts for exhaust gas treatment were prepared by impregnation method. The results showed that the catalyst supported by ceria-zirconia solid solution synthesized via coprecipitation method possessed lower ignition temperature, via hydrothermal method bear the highest conversion. While the solid solution prepared with solid state reaction exhibited the poor catalytic performance compared with others. For the conversion of CO, the ignition temperature was increased with increase of Pd supported. For the conversion of CH4, the rule was opposite. Moreover, the investigation showed that there is intimate relationship between the structure of solid solution and catalyst performance. The support with larger specific surface area, uniform pore diameter distribution showed better catalytic reaction performance更多还原