形貌调变的介孔碳硅复合纳米材料的制备及其催化性能的研究

发布时间：2018-06-25 09:19

本文选题：发散状孔道 + 200nm颗粒尺寸　；参考：《华东师范大学》2015年硕士论文

【摘要】：颗粒尺寸小于200 nm,特别是具有中心发散状孔道结构的树枝状介孔纳米颗,因具有大的开放性孔道、高的可接触内表面积及小的颗粒尺寸,在细胞成像、疾病诊断、药物/基因/蛋白质储存或传递、分离及多相催化方面有潜在应用价值。很多科学家已经成功制备具有发散状孔道结构的二氧化硅介孔纳米颗粒,由于其表面丰富的羟基,可以通过硅烷化的方法在孔道内引入多种有机功能基团,但是由于有机硅烷化试剂价格昂贵、重复使用率低以及非晶型硅基介孔材料水热稳定性差的缺点,限制了它的应用。碳材料不存在上述缺点,并且具有良好的物理和化学稳定性、特殊的电子性质等优点,很多科学家已经成功制备了不同形貌的碳材料。但是颗粒尺寸小于200 nm、具有发散状孔道结构的MCNs的制备仍存在挑战。本文开展了三方面的研究工作,主要致力于通过调节体系pH影响正硅酸四乙酯的水解缩合速度以及酚醛树脂的缩合速度来制备具有不同形貌和结构的介孔碳硅复合纳米材料MSCN,并通过处理后得到具有不同形貌和结构特别是发散状孔道的MCNs和MSNs。第一部分,利用具有发散状孔道结构的MSNs作为硬模板,分别选用蔗糖,间苯二酚、4-硝基酚作为碳源进行浇筑,蔗糖与间苯二酚成功翻模MSNs的孔道结构,制备了具有发散状孔道结构、颗粒尺寸小于200 nm的MCNs,而4-硝基酚则不能,原因是4-硝基酚分子中只含有一个羟基,碳化过程中缩合程度不高导致；利用三聚氰胺和蔗糖作为共碳源成功制备保持球形结构的N掺杂MCNs,但三聚氰胺量要控制在5%以下。第二部分,利用软模板方法,通过调节体系pH控制TEOS的水解缩合速度以及酚醛树脂的缩合速度,进而影响酚醛树脂与硅氧负离子与表面活性剂胶束的静电作用,从而一步法得到具有不同形貌和结构的MSCN;当体系pH约为8时,得到具有发散状孔道结构的MSCN,通过后期氮气氛围下碳化、除硅或空气氛围下高温焙烧分别得到具有发散状孔道结构的MCNs以及MSNs;在pH等于8的条件下,碱源种类不影响发散状孔道的形成但是对于颗粒尺寸有影响,只有三乙醇胺作为碱源才能保持颗粒尺寸在200 nm以下,主要是三乙醇胺较强的氢键作用限制了颗粒的生长。第三部分,对不同结构的MCNs和MSNs进行磺酸化处理,利用叔丁醇和.间甲酚作为探针反应。具有发散状孔道结构的MCNs-B-1-S、MSNs-B-1-S催化该反应的转化率分别达到65%和58%,高于不同形貌的MCNs-S和MSNs-S以及其他体系催化剂,显示了发散状孔道结构的优势。
[Abstract]:The particle size is less than 200 nm, especially the dendritic mesoporous nanoparticles with a central divergent pore structure, due to their large open channels, high contact internal surface area and small particle size, in cell imaging, disease diagnosis, Drug / gene / protein storage or transmission, separation and heterogeneous catalysis have potential applications. Many scientists have successfully prepared mesoporous silica nanoparticles with divergent pore structures. Because of their abundant hydroxyl groups on the surface, many organic functional groups can be introduced into the channels by silanization. However, its application is limited due to the high cost of organosilanization reagents, low reuse rate and poor hydrothermal stability of amorphous silicon-based mesoporous materials. Many scientists have successfully prepared carbon materials with different morphologies due to their good physical and chemical stability and special electronic properties. However, the preparation of MCNs with divergent pore structure and particle size less than 200 nm remains a challenge. In this paper, three aspects of research work have been carried out. The main purpose of this paper is to prepare mesoporous carbon silicon nanocomposite MSCN with different morphology and structure by adjusting the pH of the system to influence the hydrolysis rate of tetraethyl orthosilicate and the condensation rate of phenolic resin. MCNs and MSNs with different morphologies and structures, especially divergent pores. In the first part, MSNs with divergent pore structure were used as hard template, sucrose and resorcinol 4-nitrophenol were used as carbon source respectively. The pore structure of MSNs was successfully flipped between sucrose and resorcinol. MCNs with divergent pore structure and particle size less than 200 nm were prepared, but 4-nitrophenol was not. The reason was that there was only one hydroxyl group in 4-nitrophenol molecule and the condensation degree was not high during carbonization. Using melamine and sucrose as common carbon source, N-doped MCNs with spherical structure were successfully prepared, but the amount of melamine should be controlled below 5%. In the second part, by adjusting the pH of the system, the hydrolysis rate of TEOS and the condensation rate of phenolic resin are controlled by soft template method, and the electrostatic interaction between phenolic resin and silica anion and surfactant micelle is affected. MSCN with different morphology and structure was obtained by one-step method, and MSCN with divergent pore structure was obtained when pH was about 8, which was carbonized in the later nitrogen atmosphere. MCNs and MSNs with divergent pore structure were obtained by calcination at high temperature in the atmosphere of silicon removal or air respectively. When pH was equal to 8, the type of alkali source had no effect on the formation of divergent pore, but had an effect on particle size. Only triethanolamine as the base source can keep the particle size below 200 nm, mainly because of the strong hydrogen bond between triethanolamine and triethanolamine. In the third part, different structures of MCNs and MSNs were treated by sulfation, and tert-butanol and MSNs were used. M-cresol acts as a probe reaction. The conversion rate of MCNs-B-1-Sn MSNs-B-1-S with divergent pore structure reached 65% and 58% respectively, which was higher than that of MCNs-S and MSNs-S with different morphologies and other catalysts, showing the advantage of divergent pore structure.
【学位授予单位】：华东师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O643.36;TB332

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