【作者】 廖银念；

【导师】 叶代启；

【作者基本信息】 华南理工大学 ， 环境科学与工程， 2013， 博士

【摘要】 随着经济的持续快速发展，发展与资源环境的矛盾日益突出，大气污染成了我国目前最突出的环境问题之一，很多工业过程中排放的挥发性有机废气就是一类主要气体污染物。催化氧化可将VOCs在较低的温度下转化为无害的CO₂和H₂O，是最有前景的处理方法之一，而催化剂的研发是催化氧化研究中的研究重点。CeO₂是一种重要的稀土氧化物，具有较高的储存与释放氧能力,因此被广泛应用于多相催化反应中。MnOx也是金属氧化物催化剂中对VOCs的氧化最具活性的催化剂之一，复合金属氧化物之间由于存在结构或电子间相互协同效应，其催化活性比相应的单一氧化物要高。基于以上观点，本研究以甲苯为目标污染物，合成不同形貌的CeO₂纳米材料，研究CeO₂在甲苯催化氧化过程中的形貌及尺寸效应，同时制备了MnOx-CeO₂复合氧化物纳米棒，并探讨了它们的催化氧化性能，以及对甲苯在催化剂上的氧化过程进行了简单的讨论。主要研究内容和结论如下:（1）开发了超声辅助水热法合成出CeO₂纳米棒。考察铈源、NaOH的浓度、水热反应的温度、时间、超声作用的时间等因素对形貌的形成及产率的影响。研究发现，除了硝酸铈之外，氯化铈、醋酸铈及硫酸铈能合成棒状形貌的纳米材料，相对高的NaOH浓度更有利于纳米棒的形成，同时证实了超声作用可以明显地提高纳米棒的产率。（2） CeO₂纳米颗粒可以改用硝酸铈为铈源而依照纳米棒的合成路线而制得，CeO₂纳米立方则可以改变水热反应温度和反应时间、提高NaOH溶液的浓度等条件的水热反应制备而得。在此基础上，考察了三种样品在催化氧化反应上的形貌效应，发现纳米棒由于主要暴露活性晶面（200）和（220）而表现出最优异的催化活性。（3）通过改变水热反应的时间及NaOH溶液的浓度，可以制备得不同直径及长度的CeO₂纳米棒，发现纳米棒的直径取决于NaOH溶液的浓度，直径随着碱的浓度的增加而单调递增，而长度除了受水热反应时间的影响之外，还受碱浓度的影响。通过考察不同长径比的纳米棒的催化氧化性能，发现纳米棒的催化活性与其直径之间存在密切关系，直径越小，活性越高，有着相似直径的纳米棒具有相似的活性。（4）在CeO₂纳米棒的研究基础上，在合成CeO₂的同时添加锰盐制备出不同比例的Mn-Ce复合氧化物纳米棒，通过考察它们的催化氧化性能优化出最佳比例的复合氧化物纳米棒，探讨了活性晶格氧在催化反应中所起的作用，并证实了催化剂具有优异的热稳定性。（5）利用原位透射红外光谱对CeO₂纳米棒和Mn0.85Ce0.15O₂纳米棒催化剂上甲苯的催化氧化过程进行了分析，初步地推测了甲苯的催化氧化历程。更多还原

【Abstract】 With the development of economy, the confliction between the development andenvironment became more and more prominent The air pollution was one of the most seriousproblems. The VOCs （volatile organic compounds） were the main air pollutants from theindustry. Catalytic oxidation was one of the most promising methods to degrade the VOCs tothe harmless CO₂and water. And the research emphasis of catalytic oxidation was thedevelopment of the catalysts.Ceria was an important rare-earth metal oxide with high oxygen storage capacity, whichwas extensively applied in the heterogeneous catalytic reactions. MnOx was one of the mostactive catalysts for VOCs oxidation. The mixed metal oxides were generally more active thanthe single metal oxide due to their synergistic effect between their structures. On account ofthese viewpoints, various shapes of Ce-based nanomaterials were prepared and theirmorphology-dependent catalytic activities were studied. Furthermore, the comparison ofcatalytic activities between the hollow and solid polyhedral MnOx have been done as well.The main contents and conclusions are as follows:（1） Ceria nanorods were synthesized through ultrasonic-assisited hydrothermal reactionmethod with cerium acetate and NaOH solution. The effect of synthetic conditionson the shape and yield of nanorods products, including the cerium source, the baseconcentration, the temperature and time of hydrothermal reaction and theultrasonication time, were discussed. And the optimal conditions were obtained.（2） The ceria nanopartiacles were obtained by the same route of nanorods with thecerium nitrate. The nanocubes were prepared by changing temperature and time ofthe reaction and the base concentration. Then, it was found that the nanorods werethe most active one since they mainly exposed the active planes （200）and（220）.（3）CeO₂nanorods with various aspect ratios were controllably synthesized. The lengthand diameter of CeO₂nanorods could be controlled by tuning the hydrothermalreaction time and the concentration of NaOH solution. The diameter was influencedonly by the concentration of NaOH solution. The length of the nanorods wasimpacted not only by the reaction time, but also by the concentration of NaOHsolution. The catalytic activities were related with the diameter of the nanorods.The smaller the diameter, the better the performance, and the samples with the similar diameter had the similar activity.（4） On the basis of the research on ceria nanorods, various content of Mn were addedinto ceria to form the nanorod-structured Mn-Ce mixed oxides. The best catalysthas been optimized. The effect of the active lattice oxygen and the stability of thecatalyst were both studied.（5） The mechanism for toluene oxidation has been deduced preliminarily through themeans of in situ FTIR.更多还原