【作者】 杨晓敏；

【导师】 邱介山； Jeroen A.van Bokhoven；

【作者基本信息】 大连理工大学 ， 化学工艺， 2010， 博士

【摘要】 随着人们对环境问题的日益关注,开发环境友好的新型催化材料和工艺路线引起研究者的广泛关注。多相催化技术是发展绿色化学方法的关键之一。本文针对负载型纳米金、钌催化剂的催化氧化性能进行研究,考察其催化醇类化合物选择氧化及CO氧化反应的性能。采用原位表征技术考察工作状态负载型金催化剂的结构,以建立催化剂结构和催化性能之间的关系,进而对反应机理进行深入分析。主要研究内容和结果如下：以氧气或空气为氧化剂,Au／TiO2或Ru／CNTs为催化剂,水为单一溶剂或水与另外一种有机溶剂的混合物为混合溶剂,在温和的条件下,成功实现醇类化合物高效催化选择氧化制备高附加值的醛类或酮类化合物。在苯甲醇选择氧化制备苯甲醛反应中,水显著增强Au／TiO2和Ru／CNTs的催化活性。其原因为水的存在有助于形成一种独特的乳液催化反应体系,乳滴界面的存在减弱了反应的扩散限制,加速反应的进行。水的存在利于O2在Au／TiO2催化剂表面的吸附与活化,这也是水促进Au／Ti02催化活性的可能原因。我们的研究结果证实在此独特的乳液多相催化反应体系中,负载型金、钌催化剂催化醇类化合物需氧氧化制备高附加值的醛类、酮类化合物具有应用潜力。采用新颖的微波辅助乙二醇液相还原法(MW-EG)制备了金粒径大小约为7 nm的Au／CNTs催化剂和钉粒径大小约为1-2nm的Ru／CNTs催化剂,它们均表现出较高的催化苯甲醇选择氧化活性和苯甲醛选择性。与浸渍法、沉积-沉淀法和乙二醇液相还原法相比,采用MW-EG法制备的Au／CNTs催化剂表现出较高的催化苯甲醇选择氧化活性。采用MW-EG法制备的Ru／CNTs催化剂,其催化活性明显优于采用传统浸渍法制备的催化剂的催化活性。MW-EG法为制备高活性负载型金属催化剂提供了新的研究思路,Au／CNTs和Ru／CNTs是一种新颖且具有应用潜力的醇类化合物选择氧化催化剂。采用X射线吸收光谱、原位红外光谱并结合动力学方法考察负载型金催化剂催化CO氧化反应的性能和反应机理。动力学实验结果表明：水促进Au／TiO2催化CO氧化反应的活性。原位X射线吸收光谱和红外光谱研究结果证实,水具有双重促进作用：水增加O2在负载型金催化剂表面的活化能力；水抑制碳酸盐和类碳酸盐物种的生成并促进其分解。在CO氧化反应中,负载型金催化剂的催化活性逐渐降低。红外光谱研究结果表明催化剂表面碳酸盐和类碳酸盐物种的生成是引起催化剂初始活性降低的主要原因。更多还原

【Abstract】 Due to increasing concern about environmental impact, there has been tremendous interest in developing environmentally friendly catalysts and processes in chemical synthesis and processing. Heterogeneous catalysis is a key to successful development of so-called "green chemistry". In this work, heterogeneous gold and ruthenium catalysis were investigated, which mainly focused on heterogeneous oxidation reactions such as alcohol oxidation and CO oxidation. Working gold catalysts were characterized by in situ spectroscopy, which may provide correlations between the catalyst structure and catalytic activity. Reaction mechanisms were further studied.Effective catalytic oxidation of alcohols under mild conditions has been realized in a special heterogeneous reaction system, in which supported gold or ruthenium catalysts function as catalysts, oxygen or air as oxidant, and water or the mixture of water and a kind of organic reagent like p-xylene or toluene as solvent. The unique and significant promotion effect of water has been evidenced by the selective oxidation of benzyl alcohol to benzaldehyde over Au/TiO2 and Ru/CNTs catalysts, respectively. Water helps to form unique emulsion droplets where the solid catalysts assemble at the interface. The interfaces of the emulsion droplets favor the mass transfer, resulting in the increase in the conversion of the substrate. Water facilitates O2 adsorption and activation over Au/TiO2. The present work has highlighted the potential of supported gold and ruthenium catalysts in aerobic oxidation of alcohols in the unique multiphase reaction system with water as promoting solvent.By making use of a novel microwave-assisted ethylene glycol approach (MW-EG), high performance Au/CNTs and Ru/CNTs catalysts that are novel and active for the selective oxidation of benzyl alcohol to benzaldehyde have been made. The as-prepared Au/CNTs catalysts have small gold particle size of 7 nm. The as-prepared Ru/CNTs catalysts have small ruthenium particle size of 1-2 nm. The catalytic activity of Au/CNTs by MW-EG method is much higher than that by impregnation method, deposition-precipitation method, and ethylene glycol approach. The catalytic activity of Ru/CNTs by MW-EG method is also much higher than that by traditional impregnation method. The microwave-assisted ethylene glycol approach to Au/CNTs and Ru/CNTs catalysts is novel and efficient, and will give a new impetus to the study of supported metal catalysts in the viewpoint of basic and applied science. Catalytic activities of Au/TiO2 for CO oxidation were studied. Reaction mechanisms of CO oxidation over supported gold catalysts were studied by in situ X-ray adsorption spectroscopy and infrared spectroscopy. Water helps to significantly improve the catalytic activity of Au/TiO2. Water has dual promotional functions in the reaction system:to increase the activation ability of the oxygen, and to inhibit the formation of these surface carbonate-like species and also help to their decomposition. The pronounced decrease of the initial activity of the supported gold catalysts was observed, which is caused by the accumulation of surface carbonate-like species on the surfaces of the supported gold catalysts.更多还原