具有高密度活性位的三维有序大孔基催化剂设计、制备及对柴油炭烟催化燃烧性能研究

The particulate matter (PM, mainly containing soot particles) emitted from diesel engines is a main source of urban atmospheric particulate matters (PM2.5, particle sizes <2.5 μm), and it has caused acute human health and environmental problem. The emission reduction of PM is a hot problem to be solved in the field of the environmental catalysis. The combination of traps and oxidation catalysts in the continuously regenerating particulate trap (CRT) appears to be one of the most efficient after-treatment techniques for the purification of diesel engine emissions, and the key factor of CRT technique is how to design and exploit the highly active catalysts for diesel soot combustion. In this project, three-dimensionally ordered macroporous (3DOM) oxides are planed to as the support or assistant due to improve the contact between diesel soot and catalyst, and noble metal nanopartilces (Au, Pt, Pd and so on) are planed to as the active component. A series of 3DOM oxide-supported noble metal nanopartilce catalysts are designed and synthesized by the gas bubbling-assisted membrane reduction (GBMR) method and the in-situ synthesis method just developed in our lab. Based on the research results of the structures and the physiochemical properties of the catalyst, the effects of the morphology and structure of noble-metal nanopartilces and the interface structure between support and noble-metal nanopartilces on the catalytic activity and the capability of adsorption and activation for oxygen molecule are in-depth discussed. The structure-function relationship between the atom-scale structure of active components and the density of active sites for oxygen molecule activation is determined, and then the catalysts with high density of active sites and high stability for soot combustion are designed and prepared. The catalytic reaction mechanisms for soot combustion are further revealed, which provides the theoretical and practical foundation for the further research and development of the catalysts with high active for soot combustion.

柴油车排放的炭烟颗粒物（PM）是城市大气PM2.5的主要来源之一，对环境和人类健康造成了巨大的危害，PM的减排是目前环境催化领域中一个亟待解决的热点问题。利用过滤器与催化剂相结合的连续过滤再生技术（CRT）是最有效的PM减排技术，该技术的关键问题是设计开发高活性的催化剂。本项目拟选择能够提供良好固-固接触能力的三维有序大孔（3DOM）结构氧化物为载体/助剂，以贵金属纳米颗粒（Au、Pt、Pd等）作为活性组分，利用自主研发的"气膜辅助还原法"和"原位合成法"制备该系列催化剂。深入探讨贵金属纳米颗粒的形貌、结构以及载体与贵金属纳米颗粒之间的界面结构对催化剂活化分子氧能力和催化活性的影响；建立催化剂的活性组分原子尺度结构与活性位密度间的构效关系，从而设计并制备具有高密度活性位、高稳定性的PM燃烧催化剂；揭示柴油炭烟燃烧反应催化作用机理，为进一步研发高活性PM燃烧催化剂提供理论依据和实践指导。

柴油车排放出的炭烟颗粒物(PM)是城市大气PM2.5的主要来源之一，它的有效消除是目前环境催化领域中一个亟待解决的难点问题。基于柴油炭烟颗粒物催化是一个典型的气-固-固多相复杂反应的本质，我们提出了高活性PM燃烧催化剂设计应该遵循提供良好固—固接触能力与强活化氧能力相结合的创新性学术思想。本项目利用能够提高固-固接触能力的三维有序大孔氧化物作为载体，以能够提高活化氧能力的贵金属或贵金属-氧化物复合纳米颗粒作为活性组分，设计并制备了多个系列的三维有序大孔（3DOM）氧化物担载贵金属催化剂，例如，3DOM-Ce0.8Zr0.2O2担载Au-Pt双金属（合金和核壳结构）、3DOM -LaFeO3担载Au纳米颗粒、3DOM-MnxCe1-xOδ担载Pt纳米颗粒、3DOM-SiO2担载碱金属掺杂MnOx以及3DOM-TiO2担载Au(Pt)@CdS核壳纳米颗粒等催化剂。深入探讨催化剂的制备规律，形成了气膜辅助还原法、气膜辅助还原/沉淀法、原位胶体晶体模板法等多种制备方法。同时采用多种物理测试手段对所制备催化剂进行结构和物化性能表征研究，测试了炭烟催化燃烧活性，并深入研究催化反应机理，其中，研发的3DOM-Ce0.8Zr0.2O2固溶体担载Au@Pt核壳结构纳米颗粒催化剂展示了较高的催化炭烟燃烧活性，起燃温度最低仅214 oC，这是目前文献报道的最低炭烟催化燃烧起燃温度（最高活性），另外，纳米Au@Pt核壳颗粒结构不仅能够提高Au基催化剂的热稳定性，而且还能提高Pt基催化剂的选择性（SCO2）。.在国家自然科学基金青年基金项目的资助下，通过3年的研究工作，本项目取得了一些重要研究进展。到目前为止，在Journal of Catalysis, Journal of Materials Chemistry A, Applied Catalysis B: Environmental, Catalysis Today等国际期刊上发表SCI收录论文16篇，其中，第一作者发表一区论文3篇；参加国内外学术会议15次并做口头报告13次，申请发明专利3项，授权发明专利1项。这些研究结果不仅对气-固-固多相复杂反应催化剂的设计具有重要的基础研究意义，而且为进一步研发高活性炭烟颗粒物燃烧催化剂提供了理论依据和实践基础，因而具有重要的环保意义和社会效益。