高性能碳烟燃烧复合氧化物催化剂的设计与制备

The diesel vehicle has been widely used due to its efficient fuel economy and high power performance, the removal of NOx and soot particle is still the major challenge for the after treatment technology of diesel exhaust. The diesel particulate filter (DPF) is widely developed to remove soot particle now. The combination of DPF and catalytic combustion of soot is expected to lower the temperature of soot combustion, which can promote the in situ regeneration of DPF in the exhaust temperature range. So it is very important to develop the catalyst with the high performance for soot combustion. The idea of this work is to increase the catalysts activity for soot combustion through the acceleration of oxygen activation on the surface. The effects of the doped metal oxides on the abilities of CeO2 and Co3O4 for the adsorption and activation of oxygen, the formation and the amount of the active oxygen species, the transfer and release of active oxygen species would be investigated. The effects of different exhaust components on soot combustion would be studied in detail to establish the network of reaction kinetics. The concepts of NOx oxidation, adsorption-storage, and quick decomposition will be adopted to improve the performance of soot combustion under loose contact condition. At the same time, the increase of SO2 tolerence of catalysts would be explored by the acceleration of decomposition and redcution abilities of surface sulfate species through the enhancement of steam reforming and/or water gas shift reaction. The relationship among the composition and structure of catalysts, surface property, the performance of soot combustion should be suggested after this reasearch, and the results are expected to provide the foundation for the design and preparation of catalysts with high performance for soot combustion.

柴油车具有优异燃油经济性和动力性能，其尾气排放控制技术以NOx和碳烟净化为主要特征，其中颗粒物捕集器(DPF)被广泛用于碳烟的去除。将DPF与催化燃烧相结合有望使碳烟燃烧温度降低到排气温度范围内，可实现DPF原位再生，高性能碳烟燃烧催化剂的开发是目前所需解决的关键。课题以CeO2和Co3O4为基础，从提高催化剂吸附活化氧的能力入手，通过引入其它金属氧化物，研究表面活性氧物种的形成、存在形式、传递与释放等对碳烟燃烧性能的影响规律。考察尾气中各组分对碳烟燃烧性能的影响，建立复杂体系下的动力学反应网络，确定碳烟催化燃烧的反应机理。同时在组成设计上引入NOx氧化-吸附存储-快速分解，及通过强化蒸汽重整/水汽变换加速表面硫酸盐分解和还原的理念，提高碳烟催化燃烧的活性和抗硫稳定性。通过本课题的研究，建立催化剂的组成-结构-表/界面性质-碳烟燃烧性能之间的构效关系，为制备高性能碳烟燃烧催化剂提供基础。

柴油车已成为我国机动车NOx和PM排放的主要分担者。因此，以NOx和PM净化为特征的柴油车尾气污染物排放控制成为研究的热点。以CeO2和Co3O4为基础，通过掺杂方式引入碱金属（K）或者过渡金属（Bi）都可以有效提高催化剂的反应活性。负载型的CeO2/LaMnO3催化剂具有良好的催化活性；其T50降低至410oC，催化剂经过10次循环后仍可保持良好的催化活性；与Co3O4 相比，Bi0.2Co在松散和紧密接触条件其T50分别降低90 和 75 °C；掺杂K可显著提高KxCo催化剂在松散接触条件下的活性，使T50降低130℃。.复合形式不同导致CeO2与LaMnO3之间的相互作用不同，其中负载型催化剂具有最佳的活性，这是由于在焙烧过程中部分Ce进入LaMnO3晶格，导致晶格畸变，增加了表面Mn4+/ Mn3+和活性氧物种的数量占总氧物种数量比例，进而提高其NO氧化和硝酸盐存储释放能力，提高催化剂碳烟燃烧活性。.Bi2O3-Co3O4在相对较低温度下就可以在界面处产生大量氧空穴，体相氧物种的移动能力由此得到促进。而Bi-Co界面起到了“气相氧泵”的作用,气相氧在Bi-Co界面处吸附后可通过氧空穴进一步传送至体相，因此氧的活化和碳颗粒物的反应可以在不同位点进行，即反应遵循“原料电池型”反应机理。.反应气氛中存在水对于催化剂活性（尤其在松散接触条件下）具有一定的促进作用，这是因为水的存在有利于改善催化剂-碳颗粒物接触状态或者碳颗粒物氧化的中间产物的水解；水热老化预处理对于Bi0.2Co活性未产生明显影响； Bi掺杂可以有效地抑制硫沉积，经过SO2预处理后其活性也未发生明显变化；NO的存在促进了烯酮物种的产生和异氰酸盐物种数量的增加从而促进碳烟燃烧。.钾的加入引发了Co3O4晶体微应力的增加，造成更多缺陷位点和Co3+离子的暴露；同时由于钾具有熔点极低的特性，可以增加催化剂表面流动性从而改善催化剂与碳烟颗粒物的接触状态；这是K的引入促进碳烟催化燃烧的原因。