【作者】 张栖；

【导师】 叶代启；

【作者基本信息】 华南理工大学 ， 环境工程， 2010， 硕士

【摘要】 出于燃油经济性的考虑，贫燃发动机得到了越来越广泛的应用，然而，贫燃发动机尾气中富含大量的氮氧化物(其中90%以上是NO)和氧，使得传统的汽车尾气净化三效催化剂在贫燃工况下失去了催化活性，因此，开发出新型的适合贫燃条件下机动车尾气净化的催化剂势在必行。Ag/AlB2BOB3B催化剂是目前烃类选择性催化还原NO反应中研究最广泛的，它具有较好的反应活性及良好的水热稳定性，但该催化剂的低温反应活性低、反应温度范围窄。为提高催化剂的低温活性及拓宽反应温度范围，本文采用浸渍法制备了以储氧性能佳、比表面积大的CeOB2B-ZrOB2B-AlB2BOB3B复合氧化物为载体，Ag，Rh为活性金属的单组分及双组分催化剂。通过多种表征手段考察了不同Ce/Zr比CZA载体的结构、热稳定性及储氧量等性能；通过活性评价和其他表征手段考察和研究了各催化剂体系的吸附性能、反应活性、反应条件对活性的影响及催化反应机理等。研究结果表明，在铈锆固溶体中加入氧化铝使得复合氧化物具有更好的热稳定性及高的储氧性能，更适于用作贫燃机动车尾气净化催化剂的载体材料。以CZA(0.5)为载体的催化剂反应活性高于CZA(0.75)担载的催化活性，其中，双组分催化剂的反应活性又高于单组分催化剂的活性，Ag(0.04)-Rh(0.007)/CZA(0.5)是反应活性最高的催化剂，它催化作用下的NO转化率可达到90.3%，且该反应的起燃温度低，活性温度范围宽(300℃～500℃)。原位红外结果显示，在Ag-Rh/CZA催化剂作用下的丙烯还原NO反应过程如下：丙烯首先被部分氧化成羧酸盐类，NO被氧化成硝酸盐类，丙烯氧化产物与硝酸盐类反应生成反应中间体酰胺基，反应中间体再进一步与NO等反应生成目的产物。在反应过程中，活性组分Rh的存在不仅有利于催化剂表面NO及CB3BHB6B等反应物的吸附，而且能促进Ag催化生成关键反应中间体-CO-NH-，进而显著提高NO的转化率。更多还原

【Abstract】 The application of lean-burn engine is rising now for the more effective burning andmore economy. However, the traditional three-way catalyst would be ineffective under thislean-burn conditions，because of the significant increment of NOBx B(the content of NO>90%)and oxygen among the exhaust of lean-burn engine. Therefore, a new type of catalyst forautomobile exhaust purification under lean-burn condition is urgently needed to be developed.The selective catalytic reduction of NO by hydrocarbons over Ag/AlB2BOB3B catalyst is consideredto be the most effective way to remove NO from the exhaust gas, the Ag/AlB2BOB3B catalyst hashigh catalytic active and good thermal stability, however, it is inactive at low Ttemperature, andits Tactivity window is also TnarrowT.To improve the catalyst activity at low temperature and broaden the activity window, aseries of (Ag)-(Rh)/CZA catalysts were prepared by impregnation methods, usingCeOB2B-ZrOB2B-AlB2BOB3B(CZA) compounds as support due to its high specific surface area andoxygen storage capacity(OSC). The characters of the structure, thermal stability, and the OSCduring the different Ce/Zr ratio CZA compounds were characterized using kinds oftechnologies. By combining the catalytic performances and the characterized methods, thecatalysts adsorption, catalytic activities, effected factors and the reactive mechanism havebeen investigated.The results showed that the CZA which formed by adding the AlB2BOB3B into the CeBxBZrB1-xBOB2Bcompound, have the high thermal stability and OSC, and is more suitable for the lean-burnautomobile exhaust catalyst carrier material.The activities of the catalysts which use the CZA(0.5) as support were higher than theCZA(0.75) catalysts, the Ag-Rh catalysts exhibited higher catalytic performances than thesingle-component Ag or Rh catalysts. The highest NO conversion is reached at 90.3% overthe Ag(0.04)-Rh(0.007)/CZA(0.5) catalyst, accompanied by the lower light-off temperatureand wider activity window (300℃～500℃).According to the in situ DRIFTS results, the process of the NO reduction reaction byCB3BHB6B over Ag-Rh/CZA catalyst is as following: oxidation of CB3BHB6B is the first part of all,formed the carboxylate, NO is oxidized into nitrate, and the oxidation products can react witheach other which produced the crucial intermediate of -CO-NH-, the intermediate furtherreacts with NO and achieve the objective response.In this reaction, the existence of Rh not only favored the adsorption of reactants such asNO and CB3BHB6B on the catalyst surface, but also promoted the formation of crucial intermediate of -CO-NH- by Ag, thus enhancing the NO conversion notably.更多还原