磁性高分子纳米粒子负载型Pd催化剂的制备、应用及催化机理研究
发布时间：2019-04-24 22:01
【摘要】：Pd催化的C-C偶联反应是构建有机化合物中C-C键最为有效且温和的方法。在此类反应中,均相Pd催化剂的催化活性很高,但也存在贵金属难回收和环境污染等问题。因此,一系列的负载型Pd催化剂被研究和发展起来。与均相Pd催化剂相比,负载型Pd催化剂催化活性较低,催化机理存在争议,通过载体结构和实验研究方法的合理设计有望解决这些问题。磁性高分子纳米粒子负载型Pd催化剂不仅催化活性高、稳定性好,而且可以通过一个外加磁场快速分离,操作更加简易,同时也为其催化机理的研究提供了便利的实验条件,因此被广泛的应用于C-C偶联反应中。此外,随着人类社会的发展,绿色化学逐渐成为了化学发展的新目标,开发能在绿色介质里使用的负载型Pd催化剂具有很大的现实意义。本课题工作设计合成了两种磁性高分子纳米粒子负载型Pd催化剂Fe_3O_4@SiO_2-Dendrimer-Pd和Pd/Fe_3O_4@PMAA-Met,并通过FT-IR、VSM、TEM、AAS、XPS等表征手段对其结构和性质进行了检测。然后,将这两种催化剂用于绿色介质中的Suzuki反应和Heck反应中,考察了它们的催化活性、循环使用性能和催化机理,具体结果如下:1.将氨基化修饰的Fe_3O_4@SiO_2-NH_2逐步与丙烯酸甲酯和3,3’-二氨基二丙胺反应合成了二代的磁性树枝状高分子载体,负载Pd后得到了纳米催化剂Fe_3O_4@SiO_2-Dendrimer-Pd。该催化剂仅以0.009 mol%的Pd用量就可高效催化无溶剂Heck反应和EtOH/H_2O中的Suzuki反应,分离产率分别可达73%-99%和84%-98%。此催化剂可通过磁铁快速分离,在无溶剂Heck反应中循环使用5次仍取得88%的产率。热过滤实验结果显示此催化剂以非均相催化机理催化Suzuki反应进行。2.采用二甲双胍对聚甲基丙烯酸包覆的磁性纳米粒子Fe_3O_4@PMAA修饰,负载Pd后制备了纳米催化剂Pd/Fe_3O_4@PMAA-Met。该催化剂仅以0.01-0.0007mol%的Pd用量就可在Et OH/H_2O中高效催化Suzuki反应,产率达74%-99%,TOF值高达125714 h-1。此催化剂可用磁铁快速分离,连续使用12次后分离产率仍可达到88%。3.过滤实验结果显示Pd/Fe_3O_4@PMAA-Met在EtOH/H_2O、70oC的Suzuki反应中存在“释放与捕捉”现象,结合不同催化剂用量的动力学曲线、Hg(0)中毒实验和相轨迹曲线等研究的结果,证明了该催化剂以均相催化机理催化Suzuki反应进行。
[Abstract]:Pd-catalyzed C / C coupling reaction is the most effective and mild method for the construction of C _ (C) bond in organic compounds. In this kind of reaction, homogeneous Pd catalyst has high catalytic activity, but there are also some problems such as difficult recovery of precious metals and environmental pollution. Therefore, a series of supported Pd catalysts have been studied and developed. Compared with homogeneous Pd catalyst, the catalytic activity of supported Pd catalyst is lower and the catalytic mechanism is controversial. The reasonable design of carrier structure and experimental research method is expected to solve these problems. Magnetic polymer nanoparticles supported Pd catalyst not only has high catalytic activity and good stability, but also can be separated quickly by an external magnetic field, which is easier to operate, and also provides a convenient experimental condition for the study of its catalytic mechanism. Therefore, it has been widely used in C / C coupling reaction. In addition, with the development of human society, green chemistry has gradually become a new goal of chemical development. It is of great practical significance to develop supported Pd catalysts which can be used in green media. Two kinds of magnetic polymer nanoparticles supported Pd catalysts Fe_3O_4@SiO_2-Dendrimer-Pd and Pd/Fe_3O_4@PMAA-Met, were designed and synthesized by FT-IR,VSM,TEM,AAS,. Its structure and properties were characterized by XPS and other characterization methods. Then, these two catalysts were used in Suzuki reaction and Heck reaction in green medium, and their catalytic activity, recycling performance and catalytic mechanism were investigated. The specific results are as follows: 1. The second generation magnetic dendrimer was synthesized by the step-by-step reaction of amino modified Fe_3O_4@SiO_2-NH_2 with methyl acrylate and 3,3-diaminodipropylamine. Nano-catalyst Fe_3O_4@SiO_2-Dendrimer-Pd. was prepared by loading Pd. The catalyst can efficiently catalyze solvent-free Heck reaction and Suzuki reaction in EtOH/H_2O at the dosage of Pd of 0.009 mol%, and the separation yields can reach 73% ~ 99% and 84% ~ (98)%, respectively. The catalyst can be separated rapidly by magnet, and 88% yield can be obtained when the catalyst is reused for 5 times in solvent-free Heck reaction. The results of thermal filtration experiments show that the catalyst is catalyzed by heterogeneous catalytic mechanism for Suzuki reaction. 2. The magnetic nanoparticles Fe_3O_4@PMAA coated with poly (methacrylic acid) were modified by metformin, and then loaded with Pd, the nano-catalyst Pd/Fe_3O_4@PMAA-Met. was prepared. The catalyst can efficiently catalyze the Suzuki reaction in Et OH/H_2O at the dosage of 0.01% Pd and 0.0007mol%. The yield is 74% and the TOF value is as high as 125714 h / 1.The yield of the catalyst is 74% ~ 99% and the TOF value is as high as 125714 h / ml. The catalyst can be separated quickly by magnet, and the separation yield can still reach 88% after 12 consecutive use. 3. The results of filtration experiments showed that there was a phenomenon of "release and capture" of Pd/Fe_3O_4@PMAA-Met in Suzuki reaction of EtOH/H_2O,70oC, which combined with the kinetic curves of different amount of catalyst. The results of Hg (0) poisoning experiment and phase trajectory curve show that the catalyst is catalyzed by homogeneous catalytic mechanism for Suzuki reaction.
【学位授予单位】：兰州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36
[Abstract]:Pd-catalyzed C / C coupling reaction is the most effective and mild method for the construction of C _ (C) bond in organic compounds. In this kind of reaction, homogeneous Pd catalyst has high catalytic activity, but there are also some problems such as difficult recovery of precious metals and environmental pollution. Therefore, a series of supported Pd catalysts have been studied and developed. Compared with homogeneous Pd catalyst, the catalytic activity of supported Pd catalyst is lower and the catalytic mechanism is controversial. The reasonable design of carrier structure and experimental research method is expected to solve these problems. Magnetic polymer nanoparticles supported Pd catalyst not only has high catalytic activity and good stability, but also can be separated quickly by an external magnetic field, which is easier to operate, and also provides a convenient experimental condition for the study of its catalytic mechanism. Therefore, it has been widely used in C / C coupling reaction. In addition, with the development of human society, green chemistry has gradually become a new goal of chemical development. It is of great practical significance to develop supported Pd catalysts which can be used in green media. Two kinds of magnetic polymer nanoparticles supported Pd catalysts Fe_3O_4@SiO_2-Dendrimer-Pd and Pd/Fe_3O_4@PMAA-Met, were designed and synthesized by FT-IR,VSM,TEM,AAS,. Its structure and properties were characterized by XPS and other characterization methods. Then, these two catalysts were used in Suzuki reaction and Heck reaction in green medium, and their catalytic activity, recycling performance and catalytic mechanism were investigated. The specific results are as follows: 1. The second generation magnetic dendrimer was synthesized by the step-by-step reaction of amino modified Fe_3O_4@SiO_2-NH_2 with methyl acrylate and 3,3-diaminodipropylamine. Nano-catalyst Fe_3O_4@SiO_2-Dendrimer-Pd. was prepared by loading Pd. The catalyst can efficiently catalyze solvent-free Heck reaction and Suzuki reaction in EtOH/H_2O at the dosage of Pd of 0.009 mol%, and the separation yields can reach 73% ~ 99% and 84% ~ (98)%, respectively. The catalyst can be separated rapidly by magnet, and 88% yield can be obtained when the catalyst is reused for 5 times in solvent-free Heck reaction. The results of thermal filtration experiments show that the catalyst is catalyzed by heterogeneous catalytic mechanism for Suzuki reaction. 2. The magnetic nanoparticles Fe_3O_4@PMAA coated with poly (methacrylic acid) were modified by metformin, and then loaded with Pd, the nano-catalyst Pd/Fe_3O_4@PMAA-Met. was prepared. The catalyst can efficiently catalyze the Suzuki reaction in Et OH/H_2O at the dosage of 0.01% Pd and 0.0007mol%. The yield is 74% and the TOF value is as high as 125714 h / 1.The yield of the catalyst is 74% ~ 99% and the TOF value is as high as 125714 h / ml. The catalyst can be separated quickly by magnet, and the separation yield can still reach 88% after 12 consecutive use. 3. The results of filtration experiments showed that there was a phenomenon of "release and capture" of Pd/Fe_3O_4@PMAA-Met in Suzuki reaction of EtOH/H_2O,70oC, which combined with the kinetic curves of different amount of catalyst. The results of Hg (0) poisoning experiment and phase trajectory curve show that the catalyst is catalyzed by homogeneous catalytic mechanism for Suzuki reaction.
【学位授予单位】：兰州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36
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