【作者】 袁书华；

【导师】 陈耀强；

【作者基本信息】 四川大学 ， 物理化学， 2007， 博士

【摘要】 近年来，由机动车尾气造成的空气污染得到了越来越广泛的关注。机动车尾气净化催化剂的使用可以有效地消除尾气中的碳氢化合物（HC）、氮氧化合物（NOx）和一氧化碳（CO）等有害物质。随着排放标准的不断提高，对催化剂的性能提出越来越严格的要求。本文制备出了高性能稀土储氧材料(Ce_0.45Zr_0.45La_0.05Y_0.05Ox)和耐高温高比表面材料（稳定的Al₂O₃），用这两种材料做载体备出了性能优异的机动车尾气净化催化剂，对催化剂的催化活性、耐久性、快速起燃以及贵金属活性组分的合理利用等方面进行了详细的考察，并对催化剂在摩托车尾气净化中的应用进行了研究。以下是本文的研究内容和结果。（1）胶溶法制备的稳定的Al₂O₃（La-Al₂O₃，La-Ba-Al₂O₃和Ce-Zr-Al₂O₃）具有优异的织构性能和高温稳定性，经1050℃高温老化后，仍有120 m²·g^-1以上的比表面积，0.40 cm³·g^-1左右的孔容；共沉淀制备的四组分稀土储氧材料Ce_0.45Zr_0.45La_0.05Y_0.05Ox同样具有优异的织构性能和高温稳定性，同时还具备高的储氧能力，经1050℃高温老化后的OSC达到284.3μmol·g^-1，且仍然保持了完整的立方晶相。两种材料完全能够满足制备高性能机动车尾气净化催化剂的需求。（2）在对单Pd催化剂的考察中发现，La和Ce的共同使用是助剂的最佳添加方式；储氧组分对单Pd催化剂是不可缺少的成分，以载体的形式加入效果更好，含量在35wt％到65wt％之间；Ba的添加有利于NOx的转化，但对HC的转化有一定的不利影响，要根据催化剂的用途而选择使用。（3）在对低贵金属含量Pt-Rh型催化剂的考察中，得到了贵金属含量与涂覆量之间的最佳比例关系，有利于贵金属的充分利用。（4）制备出的高性能Pd-Rh型双涂层催化剂，表现出优异的低温起燃、快速转化和抗高温老化能力，该催化剂在与三家国外公司催化剂样品性能对比测试中，综合性能、尤其是抗高温能力达到、甚至超过所对比样品。（5）制备了汽油车中偶催化剂，在JETTA-MT车上的检测结果达到欧Ⅲ排放标准，测试值只有欧Ⅲ排放限制值的50％左右，有助于我国欧Ⅲ排放标准的按时实施。（6）制备了压缩天然气（CNG）汽车中偶催化剂，在JETTA-MT车上的检测结果达到欧Ⅲ排放标准，测试值剩与由实验得到的劣化系数只有限制值的50％左右，对我国CNG车欧Ⅲ排放标准的实施具有重要的意义。（7）针对摩托车尾气排放的特征，详细设计和制备了多种类型、多种规格的催化剂，并对催化剂性能进行综合评价，结果表明各种类型的催化剂均表现出低的起燃温度、优异的快速起燃性能和抗老化性以及宽的空燃比窗口。其中单Pd催化剂表现出良好的氧化性能；Pd-Rh型催化剂具有优异的氧化性能和对NOx较好的转化性能；Pt-Rh型催化剂具有出色的低温催化活性和非常宽的空燃比窗口；Pt-Pd-Rh型催化剂具有前三种催化剂的综合优势，并表现出高的性价比。（8）在摩托车尾气净化催化剂的应用中，工况法欧Ⅲ排放测试得到十分突出的净化效果，在与其他催化剂的对比测试中具有非常明显的性能优势和性价比优势。该结果对我国摩托车尾气排放满足欧Ⅲ标准的实施提供了有力的技术支持和应用保证。（9）以上催化剂的成功研制和应用与催化材料的优异织构性能和稳定性能密切相关。更多还原

【Abstract】 In recent years, more and more attention has been paid to the air pollution result from the automobile exhaust gas. The exhaust catalysts can remove the harmful hydrocarbons （HC）, nitrogen oxides （NOx） and carbon monoxide （CO）. Along with the strict emission standards, more and more requests for the performance of the catalysts are put forward. A rare earth oxygen storage material (Ce_0.45Zr_0.45La_0.05Y_0.05O₂) with excellent performance and the thermal-resistant materials （stabilized Al₂O₃） with high specific surface area were prepared in this paper. Many kinds of exhaust catalyst were prepared using the two kinds of support material. The catalytic activity, durability, fast light-off performance and precious metals distribution of the catalysts, etc. were investigated in detail. Many researchs in the application of motorcycle exhaust catalysts were carried out. The main contents and results in this thesis can be summarized as follow:（1） Stabilized Al₂O₃ （La-Al₂O₃, La-Ba-Al₂O₃ and Ce-Zr-Al₂O₃） prepared with Gel-Solution method has excellent performance in textural structure and thermal stability, so as the oxygen storage material （OSM, Ceo.45Zro.45Lao.05Yo.05Ox）. In addition, the OSM has good oxygen storage capacity （OSC）. After aged at 1050℃, the specific surface area (S_BET) is up to120 m².g^-1 for stabilized Al₂O₃, the OSC is up to 284.3μmol.g^-1 for OSM. Two kinds of material still keep single phase. Two kinds of support material can satisfy completely the request of preparing exhaust catalysts.（2） After the investigation of Pd only catalysts, some results are obtained. The common usage of the La and Ce additives is the best way to promote the catalytic activity of Pd only catalyst. The OSM is an indispensable composition to Pd only catalyst, the best content is within 35 wt% and 65 wt%. Ba additive can enhance NOx conversion, but has a disadvantage influence to HC conversion.（3） The optimal ratio between the precious metals （PM） content and the coating weight is obtained after the investigation of low precious metals content Pt-Rh catalyst. This result is advantageous to the economical usage of the precious metals in preparing catalysts.（4） Pd-Rh catalyst with double coating layers was prepared elaborately. The catalyst possesses excellent catalytic activity, durability and fast light-off performance. It shows better performance than that of the three foreign catalyst samples, especially the high thermal stability. （5）Medium-Coupled Catalysts （MCC） meeting gasoline vehicles EU III emission standards were prepared elaborately. The encapsulated MCC was tested in a JETTA-MT gasoline vehicle according to the LDECE2000 test recycle. The values of HC, CO and NOx given by the results are only 65.5 %, 61.8 % and 38 % of the value of the EU III emission standards, which shows that the MCC not only has good low temperature activity but also has high thermal stability. The high performance MCC will help to bring the EU III emission standards into effect on time in China.（6） The MCC meeting CNG vehicles EU III emission standards was prepared elaborately also. It was tested in a JETTA-MT CNG vehicle according to the LDECE2000 test recycle. The test value of CH₄, CO and NOx given by the results are only about 50% of the value of the EU III emission standards. The MCC for CNG vehicles will help to bring the EU III emission standards into effect in China.（7） According to the characteristics of motorcycle exhaust gas, various types and specifications of catalysts were designed and prepared elaborately. The results of evaluation that the catalysts have low light-off temperature, fast light-off performance, high thermal stability and a wider A/F window. Pd only catalyst shows good oxidizing performance. Pd-Rh catalyst shows good performance for oxidizing CO and reducing NOx. Pt-Rh catalyst shows excellent catalytic activity at low temperature and wide A/F window. Pt-Pd-Rh catalyst possesses excellent qualities of the three catalysts mentioned above and shows the price advantage.（8） Compared with other catalysts, the motorcycle exhaust catalysts prepared in this thesis show the the best performance in the recycle test, which will help to bring the motorcycle EU III emission standards into effect on time in our country.（9） The excellent performance of all kinds of catalyst prepared is based specially on the excellent textural structure and stability of support materials.更多还原