树枝状介孔纳米球的绿色合成及其催化反应性能的研究

发布时间：2018-02-03 00:45

本文关键词： 介孔二氧化硅纳米球树枝状孔道共表面活性剂　出处：《华东师范大学》2017年硕士论文　论文类型：学位论文

【摘要】：介孔硅材料因具有优异的孔道结构、大的比表面积、特殊的表面性能,自首次报道合成就备受关注,它为生物和工业应用提供了载体,打开了负载大分子功能材料的大门。尺寸小于200 nm的介孔硅球由于短的扩散路径和易于接触的反应活性中心更是在催化反应领域引起了广泛的关注。本论文在本课题组对树枝状介孔材料合成的已有研究基础上,根据其合成机理,进一步探究树枝状介孔硅球的绿色合成方法,同时以这些纳米颗粒为载体制备不同催化剂,对比它们与传统介孔材料MCM-41的催化性能。文章第一部分以十六烷基三甲基溴化铵为表面活性剂,通过添加不同碳链长度的二羧酸盐为共表面活性剂,成功制备出树枝状介孔纳米硅球。当改变共表面活性剂碳链的长度,可以细微调控纳米颗粒的尺寸并能调节树枝状孔道的开放程度,而且在实验探究的范围内,使用共表面活性剂的碳链越长,其树枝状孔道结构也就越明显。文章第二部分在第一部分的基础上,通过在合成过程中原位引入钛源,一步法合成了树枝状孔道结构的含钛纳米硅球。而且同样可以通过调节共表面活性剂碳链的长度来调节树枝状孔道的开放程度。由于过渡金属杂原子易于水解的特性,文章还分别使用水解较慢的TDA与水解较快的TBOT为钛源制备树枝状含钛纳米硅球进行环己烯环氧化的实验,对比它们与传统Ti-MCM-41的催化活性,发现以TDA为钛源制备的催化剂的催化反应性能与Ti-MCM-41相当,而且其TON值要远高于Ti-MCM-41,实现了钛源的高度利用。此外文章还考察催化剂结构与钛源种类、共表面活性剂的关系,研究钛源水解速率和共表面活性剂碳链长度变化对催化剂反应性能的影响。文章第三部分尝试使用无碱法合成树枝状介孔二氧化硅纳米颗粒,该方法在不外加碱源的情况下成功利用共表面活性剂合成树枝状介孔二氧化硅纳米颗粒,该方法操作简单、成本低、污染小,满足环境保护和可持续发展要求。用这种方法制备负载银纳米颗粒的催化剂进行苯甲醇的催化氧化实验,其反应性能也要优于传统催化剂。
[Abstract]:Because of its excellent pore structure, large specific surface area and special surface properties, mesoporous silicon has attracted much attention since the first report on synthesis. It provides a carrier for biological and industrial applications. Doors open for loaded macromolecular functional materials. Dimensions less than 200. The mesoporous silica spheres at Nm have attracted much attention in the field of catalytic reaction because of their short diffusion paths and easy to contact reactive centers. In this paper, we have studied the basis of the synthesis of dendritic mesoporous materials. Go. According to the synthesis mechanism, the green synthesis method of dendritic mesoporous silica spheres was further explored, and different catalysts were prepared on these nanoparticles. In the first part, cetyltrimethylammonium bromide was used as surfactant and dicarboxylate with different length of carbon chain was added as cosurfactant. The dendritic mesoporous nanocrystalline silica spheres were successfully prepared. When the length of the carbon chain of the cosurfactant was changed, the size of the nanoparticles and the opening degree of the dendritic channels could be adjusted slightly, and within the scope of experimental investigation. The longer the carbon chain is used, the more obvious the dendritic pore structure will be. The second part is based on the first part, through the in-situ introduction of titanium source in the synthesis process. Titanium nanocrystalline silica spheres with dendritic pore structure were synthesized by one step method. The opening degree of dendritic channels can also be adjusted by adjusting the length of the carbon chain of co-surfactants. Characteristics. The cyclohexene epoxidation of dendrimer nanocrystalline silica spheres was prepared by using slow hydrolyzed TDA and fast hydrolyzed TBOT as titanium source. Comparing their catalytic activity with traditional Ti-MCM-41, it was found that the catalytic activity of the catalyst prepared with TDA as titanium source was comparable to that of Ti-MCM-41. The TON value of the catalyst is much higher than that of Ti-MCM-41, which realizes the high utilization of titanium source. In addition, the relationship between the structure of catalyst and the type of titanium source and the co-surfactant is also investigated. The effects of the hydrolysis rate of titanium source and the length of carbon chain on the reaction performance of the catalyst were studied. In the third part, dendritic mesoporous silica nanoparticles were synthesized by alkaline-free method. The method successfully synthesized dendritic mesoporous silica nanoparticles without adding alkali source. The method is simple in operation, low in cost and less in pollution. In order to meet the requirements of environmental protection and sustainable development, the catalytic oxidation of benzyl alcohol over the catalysts supported on silver nanoparticles by this method is also superior to that of the traditional catalysts.
【学位授予单位】：华东师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB383.1;O643.36

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