【作者】 张明；

【导师】 叶代启；

【作者基本信息】 华南理工大学 ， 环境科学， 2011， 硕士

【摘要】 当前,柴油机动车因具有良好的动力性和经济性,更有着节能环保的优势在世界各国得到广泛的使用,但其排气中的污染物特别是碳烟颗粒物给城市环境来了严重的影响。排气后处理技术中颗粒物过滤器(DPF)作为柴油车排气碳烟消除最有效且实用的方法在柴油车排气处理装置中广为使用,但需在DPF内壁上涂覆贵金属型催化剂,而贵金属资源日益短缺,且价格昂贵等因素正引领着众多前沿研究者将催化剂设计推向其它可替代金属或金属(复合)氧化物。基于此,本文将MnOx-CeO2为研究对象,研究将其用于催化氧化碳烟的性能。本文将Mn引入CeO2以期提高其储氧和氧化还原性能,并将其用于催化氧化柴油车排气碳烟,通过比表面积(BET)、X射线衍射(XRD)、程序升温还原(TPR)、程序升温脱附(TPD)、X射线电子能谱(XPS)、原位漫反射傅里叶变换红外光谱(In-situ DRIFTS)等表征手段研究该催化剂特性与碳烟氧化活性的关联。另结合柴油车排气特点,在活性评价和原位红外测试中引入NO,探讨了NO和O2在催化剂表面形态及其演变与碳烟氧化的关联,并推断机理。经过研究得出以下主要结论：1)用共沉淀法将Mn引入CeO2后,MnOx-CeO2催化剂形成了仍具有立方相萤石结构固溶体,氧化还原性能提高,同时促生了比CeO2更多的氧空位,有利于气相氧在催化剂表面上的吸附、活化和迁移,催化剂表面生成丰富的氧物种(O2-,O-,O2-)。2)MnOx-CeO2复合氧化催化剂比MnOx, CeO2能显著地降低碳烟的起燃温度,在O2气氛下,催化剂对碳烟的活性与其表面原子吸附氧O-密切相关；当引入NO至反应气氛中,更提升了各催化剂对碳烟的氧化活性,而这与催化剂对NO较强氧化活性和NOx存储性能密切关联。3)NO吸附于MnOx, CeO2和MnOx-CeO2催化剂后可被表面氧物种(O2-,O-,O2-)氧化并生成NO2-,NO3-等物种并储存,O2的引入更促进了NO向NO2-,NO3-物种的氧化,同时因MnOx-CeO2复合氧化物具有NO3-存储能力有利于碳烟氧化。4)在碳烟催化氧化反应中,MnOx(z)-CeO2系列催化剂上生成的碳氧中间物种C(O)不仅能与气相中的O2,NO2反应生成CO2,还可与其表面存储的NO3-直接发生反应而被氧化。更多还原

【Abstract】 Nowadays, diesel motor vehicles are widely used in many countries all over the word for their good performance and high fuel economy, also because of the advantage of saving energy and environmental protection, however, serious environmental impact are brought out because of pollutans especially soot from exhaust. Diesel Particulat Filter (DPF) as one kind of after-treatment technology is widely applied for its effective and functional method for soot elimination, but precious metal catalyst are needed to be coated on the wall in the DPF, while because precious metals resources are growing shortages and expensive, other alternative metal or metal (composite) oxides are anticipated by many frontier researchers. Based on these points, MnOx-CeO2 was applied as the research object in this paper to study the performance of catalytic soot combustion.Mn was introduced into CeO2 in order to improve oxygen storage and redox performance, and applied for catalytic oxidation of diesel soot, BET specific surface area (BET), X-Ray diffraction (XRD), Temperature Programmed Reduction (TPR), Temperature Programmed Desorption (TPD), X-ray Photoelectron (XPS), In-situ Diffuse Fourier Transorm Infrared Spectroscopy (In-situ DRIFTS) are used to study the correlation between catalyst features and soot oxidation activity. In addition, considering the characteristics of diesel exhaust, NO was introduced in the reaction atmosphere of TPO and In-situ DRIFTS test in order to explore the correlation between morphology and evolution of NO/O2 and soot oxidation, and then the mechanism was inferred.The main conclusion were concluded after the study:1) With Mn introduced into CeO2 by coprecipitation method, MnOx-CeO2 still has formed a cubic phase fluorite structure, redox ability was improved greatly, and more oxygen vacancies were produced compared with CeO2, thus being good for the adsorption, activation and migration of gas oxygen on the catalyst, also rich surface oxygen species are formed (O2-,O-,O2-).2) MnOx(z)-CeO2 series catalysts could obviously reduce the light-off temperature of soot compared with pure MnOx and CeO2, with oxygen existed, the activity of catalysts were correlated well with the atomic adsorptive oxygen(O-); While NO was added into the reation atmosphere, the activity was greatly improved, which had close association performance with the high NO oxidation ability and NOx storage ability.3) NO could be oxidized to NO2-, NO3- by surface oxygen species (O2-, O-, O2-) on MnOx, CeO2 and MnOx-CeO2 catalysts, while the introduction of O2 gas would improve the NO oxidation ability to NO2-, NO3-, the soot oxidation could be improved because of high NO3- storage ability by MnOx-CeO2 complex oxides 4) During the soot catalytic oxidation reaction, carbon oxygen intermediate species C(O) gengrated on MnOx(z)-CeO2 series catalysts could not only react with O2, NO2 gas phase to produce CO2, also with the NO3" stored on the catalyst surface directly.更多还原