基于温敏高分子载体的催化剂的制备与应用

发布时间：2018-06-28 02:10

本文选题：温敏性 + 高分子　；参考：《浙江理工大学》2017年硕士论文

【摘要】：金属纳米粒子由于其特殊的晶体结构和表面性质常常被应用于催化领域,但由于其极高的表面活性和比表面积,金属纳米粒子之间会发生聚集而使其催化活性降低甚至失去催化活性,因此需要将金属纳米粒子负载到一定的载体上,以分散和稳定金属纳米粒子,提高其利用率。目前常用的无机载体主要有活性炭、石墨烯、碳纳米管、Al2O3、SiO2等,也有一些有机载体(如树脂),由于这些载体通常是不溶于反应液的,因此将以这些载体负载的催化剂称为非均相催化剂。非均相催化剂在回收利用方面很方便,也有将催化剂固定在催化剂床上,但其催化效果往往并不高。相反的,以某些能溶于反应液的载体(如超支化聚乙烯亚胺)负载金属纳米粒子,可以制成均相催化剂。均相催化剂的催化效率很高,但其回收困难。温敏高分子是一类能够随温度变化发生性质极大转变的高分子。其具有一转变温度,当环境温度低于其转变温度时,温敏高分子呈亲水性,能溶于水中形成均相体系;当环境温度高于其转变温度时,温敏高分子呈疏水性,从水中析出形成非均相体系。因此若使用温敏高分子作为金属纳米粒子的载体就可以结合均相催化剂和非均相催化剂的优点。不仅如此,由于温敏高分子载体的结构会随温度的变化而变化,因此可以通过控制反应温度来控制催化反应的速率,当温敏高分子负载催化剂从体系中析出,甚至可以使催化反应停止,这样便实现了催化反应的“开”、“关”控制。另一方面,传统的催化反应通常是在有机溶剂中进行的,而由于在温敏高分子中同时存在疏水基团和亲水基团,当以温敏高分子为载体的金属纳米粒子催化剂进入催化反应体系,一些疏水性的底物会在温敏高分子的疏水区域发生聚集,提高了局部底物浓度,催化反应速率增快,因此使用温敏高分子负载催化剂可以在水相中进行催化反应。这样便在保证了催化反应速率的前提下,避免了大量有机溶剂的使用,符合“绿色化学”的理念。本文拟利用温敏高分子随温度变化会发生亲疏水性转变的温敏性能,制备出以温敏高分子为载体的高效的易分离的负载金属Pd催化剂;另一方面,试图通过控制温度来调节催化剂的催化活性,以制备出一类可控催化剂,并希望建立温敏高分子载体结构与催化剂催化活性之间的初步关系。本文以不同分子量的寡聚乙二醇甲醚甲基丙烯酸酯为温敏高分子单体、以4-乙烯基吡啶为配位单体制备了一系类高效可回收的体型温敏高分子负载Pd催化及和线型温敏高分子负载Pd催化剂。通过FTIR、NMR、XRD、DSC、TG、TEM等现代分析方法表征了温敏高分子载体及其负载Pd催化剂的结构,发现得到了Pd粒子尺寸为6-10 nm的体型温敏高分子负载Pd催化剂和Pd粒子尺寸为3.5 nm左右的线型温敏高分子负载Pd催化剂。以对硝基苯酚的催化还原为模型反应研究了不同结构温敏高分子负载Pd催化剂的催化反应动力学,分析了温敏高分子负载Pd催化剂的温敏催化效果以及温敏高分子载体结构对其催化效果的影响。最后,为了拓展温敏高分子载体的结构和应用领域,本文还制备和表征了以三苯基膦为配体的温敏高分子负载Pd催化剂,并研究了该催化剂对Suzuki-Miyaura反应的催化效果。研究发现,体型温敏高分子负载Pd纳米粒子催化剂和线型温敏高分子负载Pd纳米粒子催化剂均能有效地催化还原4-硝基苯酚为4-氨基苯酚,并且具有温敏催化效果——转变温度以下是催化反应速率快,转变温度以上时,催化反应速率慢,甚至实现了反应“开关”的控制。载体结构对催化剂效果影响颇大,线型温敏高分子负载Pd催化剂的催化效率是体型温敏高分子负载Pd催化剂的催化效率的1000多倍。线型温敏高分子对Pd纳米粒子的分散效果更好,能得到尺寸更小,单分散性更好的Pd纳米粒子。温敏高分子催化剂在循环使用8次后,仍能保持90%以上的转化率,重复使用性能良好。
[Abstract]:Metal nanoparticles are often used in the field of catalysis because of their special crystal structure and surface properties. However, because of their high surface activity and specific surface area, the metal nanoparticles will accumulate to reduce their catalytic activity and even lose the catalytic activity. Therefore, the metal nanoparticles need to be loaded on a certain carrier. The use of active carbon, Shi Moxi, carbon nanotubes, Al2O3, SiO2, as well as some organic carriers (such as resin), are commonly used in the dispersion and stabilization of metal nanoparticles. As these carriers are usually insoluble in the reaction liquid, the catalysts supported by these carriers are called heterogeneous catalysts. The catalyst is easy to recycle and immobilizing the catalyst on the catalyst bed, but its catalytic effect is often not high. On the contrary, a homogeneous catalyst can be made by loading metal nanoparticles (such as hyperbranched polyethyleneimine) with some carriers (such as hyperbranched polyethyleneimine). The catalytic efficiency of the homogeneous catalyst is very high, but the recovery is difficult. It is difficult. Thermosensitive polymer is a kind of polymer which can change greatly with temperature change. It has a transition temperature. When the environment temperature is lower than its transition temperature, the temperature sensitive polymer is hydrophilic and can dissolve in water to form a homogeneous system. When the temperature of the environment is higher than the temperature, the thermo sensitive polymer is hydrophobic and form in the water. Therefore, if the temperature sensitive polymer is used as the carrier of the metal nanoparticles, the advantages of homogeneous and heterogeneous catalysts can be combined. Not only that, because the structure of the temperature sensitive polymer carrier varies with the temperature, so the reaction rate can be controlled by controlling the reaction temperature, as Wen Min. The polymer supported catalyst can be precipitated from the system and even can stop the catalytic reaction. In this way, the "open" and "close" control of the catalytic reaction is realized. On the other hand, the traditional catalytic reaction is usually carried out in the organic solvent, and the hydrophobic group and hydrophilic group in the thermosensitive polymer are used as the thermosensitive polymer. Some hydrophobic substrates will accumulate in the hydrophobic region of the thermosensitive polymer, which improves the concentration of the substrate and the reaction rate increases rapidly. Therefore, the catalytic reaction can be carried out in the water phase by using a thermosensitive polymer supported catalyst. This ensures the catalytic reaction. On the premise of the rate, the use of a large number of organic solvents is avoided and the concept of "green chemistry" is in line with the concept of "green chemistry". In this paper, the temperature sensitive properties of thermosensitive polymers with the change of hydrophobicity will occur with the temperature change. A highly efficient and easily separated load metal Pd catalyst with a thermosensitive polymer is prepared. On the other hand, the temperature sensitive polymer is tried to control the temperature. Degree to regulate the catalytic activity of the catalyst to prepare a kind of controllable catalyst, and hope to establish a preliminary relationship between the structure of the temperature sensitive polymer carrier and the catalytic activity of the catalyst. In this paper, the oligoethylene glycol methyl ether methacrylate with different molecular weight was used as the thermosensitive polymer monomer and 4- vinyl pyridine was used as the coordination monomer. A highly efficient and recoverable type thermosensitive polymer supported Pd catalyst and a linear thermosensitive polymer loaded Pd catalyst. The structure of a thermosensitive polymer carrier and its loaded Pd catalyst was characterized by modern analytical methods such as FTIR, NMR, XRD, DSC, TG, TEM and other modern analytical methods. The Pd particle scale was found to be a 6-10 nm type thermosensitive polymer loaded Pd catalyst. The linear thermosensitive polymer supported Pd catalyst with Pd particle size of about 3.5 nm was used. The catalytic reaction kinetics of different structure thermosensitive polymer supported Pd catalysts was studied with the catalytic reduction of p-nitrophenol as a model reaction. The Wen Mincui effect of the thermosensitive polymer supported Pd catalyst and the temperature sensitive polymer carrier structure were analyzed. Finally, in order to expand the structure and application field of the temperature sensitive polymer carrier, the thermosensitive polymer supported Pd catalyst with three phenyl phosphine as the ligand was prepared and characterized, and the catalytic effect of the catalyst on the Suzuki-Miyaura reaction was studied. The catalyst and linear thermosensitive polymer supported Pd nanoparticle catalyst can effectively catalyze the reduction of 4- nitrophenol to 4- aminophenol, and have a temperature sensitive catalytic effect. The catalytic reaction rate is fast below the transition temperature, and the reaction rate is slow when the transition temperature is above, and even the reaction "switch" control is realized. Carrier structure is the same. The effect of catalyst effect is considerable, the catalytic efficiency of the linear thermosensitive polymer supported Pd catalyst is more than 1000 times the catalytic efficiency of the type thermosensitive polymer loaded Pd catalyst. The dispersion effect of the linear thermosensitive polymer on Pd nanoparticles is better, and the Pd nanoparticles with smaller size and better monodispersity can be obtained. After 8 cycles, it can still maintain more than 90% conversion rate and good reuse performance.
【学位授予单位】：浙江理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36

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