磺酸基团功能化的多孔碳纳米球的合成及催化性能的研究
发布时间：2018-10-13 15:15
【摘要】：多孔碳球(NCS)因其具有的较高的化学稳定性、较好的导电性、较低的价格,同时孔结构的引入使得其具有较大的比表面积,可控的孔道结构,可调变的径等特点,因而被广泛应用在能量高效存储和转换、催化、生物医学等方面。不同结构的多孔碳球在不同的方面有着特殊的应用。因此,许多科学家致力于多孔碳球的合成,并取得了很大的进展。在文献和课题组之前取得的一些研究成果的基础之上,在其他条件均不改变,仅通过改变表面活性剂的链长,成功制备了不同结构的介孔碳球(MCN),实现了 MCN结构由中空到发散状结构转变,并且该发散状的MCN颗粒尺寸均控制在120 nm以下。本文主要围绕如何实现不同结构的MCN的合成、机理及其功能化展开了一些研究性的工作。主要得到如下结果:1.在使用TEAH_3为碱源,其他条件相同,仅仅只简单地调变表面活性剂的链长,实现了 MCN从中空到发散状结构的合成和转变,同时结合原位跟踪体系过程中pH值的手段,发现主要是因为不同链长的表面活性剂形成胶束的CMC浓度不同,导致形成胶束的数量不同,在碱源的量相同的情况下导致胶束表面吸附的碱量不一样,这种情况下,致使胶束表面硅物种的包覆程度不一样,是实现不同结构的MCN的关键原因。2.将制备的MCN为载体,通过不同的磺酸功能化技术,探究出气相磺化法是最佳的磺酸化条件。将制备的不同结构的MCN磺酸功能化,以间甲酚与叔丁醇的烷基化反应作为探针反应,详细探究了不同碳化温度和不同结构的磺酸功能化的多孔碳纳米球(MCN-SO_3H)的催化性能,发现了最佳碳化温度的催化性能是由不同结构的MCN所决定的。3.详细探究了 MCN-SO_3H在探针反应中的循环使用效果不佳的原因:(1)反应物的吸附致使孔道被堵住,即堵孔现象。(2)MCN的载体本身是由间苯二酚-甲醛的碳前驱体合成的,探针反应使用的溶剂是间甲酚和叔丁醇。载体本身的间苯二酚的羟基会与间甲酚和叔丁醇中的羟基在酸性条件下发生反应,导致孔道可能被堵,同时底物本身参与反应的量的减少,导致得到的催化产物很少。(3)由于反应溶剂中不可避免有水的引入与生成,导致催化剂在较高的温度下-SO_3H可能会脱落。此外,通过在MCN中引入不同链长的醇,将其磺酸功能化后,实现催化剂的不同亲疏水性的调变,并探究了不同的亲疏水性的催化剂在该烷基化反应中的催化效果,同时有望在低温的壬醛与乙二醇的缩醛反应中较好的催化性能。
[Abstract]:Due to its high chemical stability, good electrical conductivity, low price, and the introduction of pore structure, (NCS) has the characteristics of large specific surface area, controllable pore structure, adjustable diameter and so on. Therefore, it is widely used in energy efficient storage and conversion, catalysis, biomedicine and so on. Porous carbon spheres with different structures have special applications in different aspects. Therefore, many scientists have made great progress in the synthesis of porous carbon spheres. On the basis of some of the research results obtained before the literature and the research group, and without change in other conditions, only by changing the chain length of the surfactant, The mesoporous carbon sphere (MCN), with different structures was successfully prepared to realize the transition of MCN structure from hollow to divergent structure, and the size of the dispersed MCN particles was controlled below 120 nm. This paper focuses on the synthesis, mechanism and functionalization of MCN with different structures. The main results are as follows: 1. When TEAH_3 was used as base source and other conditions were the same, the chain length of surfactant was simply adjusted, which realized the synthesis and transformation of MCN from hollow to divergent structure, and combined with the method of in situ tracking the pH value in the system. It was found that the amount of micelle formed was different due to the different CMC concentration of micelle formed by surfactant with different chain length, and the amount of alkali adsorbed on micelle surface was different when the amount of alkali source was the same. The different coating degree of silicon species on micelles is the key reason to realize MCN with different structure. 2. By using the MCN as carrier and different sulfonic acid functionalization techniques, it was found that the gas phase sulfonation method was the best sulfonic acid condition. The catalytic properties of sulfonic acid functionalized MCN nanospheres (MCN-SO_3H) with different carbonation temperatures and structures were investigated by using the alkylation of m-cresol with tert-butanol as a probe. It is found that the catalytic performance of the optimum carbonization temperature is determined by the different structure of MCN. The reasons for the poor recycle of MCN-SO_3H in the probe reaction were discussed in detail: (1) the adsorption of reactants resulted in the blocking of the pore channel, that is, the phenomenon of blocking the pore. (2) the carrier of MCN itself was synthesized from the carbon precursor of resorcinol-formaldehyde. The solvent used in the probe reaction is m-cresol and tert-butanol. The hydroxyl group of resorcinol in the carrier itself reacts with the hydroxyl group in m-cresol and tert-butanol in acidic conditions, which may result in the blocking of the pore channel and the reduction of the amount of the substrate itself participating in the reaction. (3) owing to the inevitable introduction and formation of water in the reaction solvent, the catalyst may fall off at a higher temperature-SO_3H. In addition, by introducing alcohol with different chain length into MCN and functionalizing its sulfonic acid, the different hydrophobicity of the catalyst was adjusted, and the catalytic effect of different hydrophilic catalyst in the alkylation reaction was investigated. At the same time, it is expected to have good catalytic performance in the acetal reaction between nonaldehyde and ethylene glycol at low temperature.
【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】：O643.36
本文编号：2269084
[Abstract]:Due to its high chemical stability, good electrical conductivity, low price, and the introduction of pore structure, (NCS) has the characteristics of large specific surface area, controllable pore structure, adjustable diameter and so on. Therefore, it is widely used in energy efficient storage and conversion, catalysis, biomedicine and so on. Porous carbon spheres with different structures have special applications in different aspects. Therefore, many scientists have made great progress in the synthesis of porous carbon spheres. On the basis of some of the research results obtained before the literature and the research group, and without change in other conditions, only by changing the chain length of the surfactant, The mesoporous carbon sphere (MCN), with different structures was successfully prepared to realize the transition of MCN structure from hollow to divergent structure, and the size of the dispersed MCN particles was controlled below 120 nm. This paper focuses on the synthesis, mechanism and functionalization of MCN with different structures. The main results are as follows: 1. When TEAH_3 was used as base source and other conditions were the same, the chain length of surfactant was simply adjusted, which realized the synthesis and transformation of MCN from hollow to divergent structure, and combined with the method of in situ tracking the pH value in the system. It was found that the amount of micelle formed was different due to the different CMC concentration of micelle formed by surfactant with different chain length, and the amount of alkali adsorbed on micelle surface was different when the amount of alkali source was the same. The different coating degree of silicon species on micelles is the key reason to realize MCN with different structure. 2. By using the MCN as carrier and different sulfonic acid functionalization techniques, it was found that the gas phase sulfonation method was the best sulfonic acid condition. The catalytic properties of sulfonic acid functionalized MCN nanospheres (MCN-SO_3H) with different carbonation temperatures and structures were investigated by using the alkylation of m-cresol with tert-butanol as a probe. It is found that the catalytic performance of the optimum carbonization temperature is determined by the different structure of MCN. The reasons for the poor recycle of MCN-SO_3H in the probe reaction were discussed in detail: (1) the adsorption of reactants resulted in the blocking of the pore channel, that is, the phenomenon of blocking the pore. (2) the carrier of MCN itself was synthesized from the carbon precursor of resorcinol-formaldehyde. The solvent used in the probe reaction is m-cresol and tert-butanol. The hydroxyl group of resorcinol in the carrier itself reacts with the hydroxyl group in m-cresol and tert-butanol in acidic conditions, which may result in the blocking of the pore channel and the reduction of the amount of the substrate itself participating in the reaction. (3) owing to the inevitable introduction and formation of water in the reaction solvent, the catalyst may fall off at a higher temperature-SO_3H. In addition, by introducing alcohol with different chain length into MCN and functionalizing its sulfonic acid, the different hydrophobicity of the catalyst was adjusted, and the catalytic effect of different hydrophilic catalyst in the alkylation reaction was investigated. At the same time, it is expected to have good catalytic performance in the acetal reaction between nonaldehyde and ethylene glycol at low temperature.
【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】：O643.36
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