钯纳米粒子的制备及催化硝基苯加氢反应研究
发布时间：2019-01-13 09:09
【摘要】：本论文从环境友好和高效催化的目的出发,以聚乙烯醇(PVA)为稳定剂,探究了水相PVA-Pd纳米催化剂催化硝基苯加氢制备苯胺。在水相中,采用氢气还原法制备了PVA-Pd纳米催化剂,Pd纳米粒子的平均粒径为3.2 nm。在较佳工艺条件下:底物与催化剂摩尔比(S/C)1:500、温度45°C、H_2压力2 MPa、反应时间3 h,硝基苯的转化率为99.30%,苯胺的选择性为100%。催化剂重复使用4次后,硝基苯的转化率仍在90%以上。以三嵌段共聚物P123(PEO20-PPO70-PEO20)为稳定剂,探究了水相P123-Pd纳米催化剂催化硝基苯加氢制备苯胺。在水相中,采用氢气还原法制备了P123-Pd纳米催化剂,Pd纳米粒子的平均粒径为2.5 nm。在较佳工艺条件下:底物与催化剂摩尔比(S/C)1:500、温度60°C、H_2压力3 MPa、反应时间1 h,硝基苯的转化率为99.40%,苯胺的选择性为100%。催化剂重复使用5次,活性和选择性均无明显变化。基于离子液体的静电位阻双重稳定作用,探究了聚醚十八胺离子液体-Pd纳米催化剂催化硝基苯加氢制备苯胺。考察了离子液体的聚合度、烷基链和阴离子对Pd纳米粒子尺寸及形貌的影响。在较佳工艺条件下:底物与催化剂摩尔比(S/C)1:2000、70°C、H_2压力2 MPa、反应时间3 h,硝基苯的转化率为96.05%,苯胺的选择性为100%,催化剂循环使用6次后,催化性能无明显变化。上述工作涵盖了制备金属Pd纳米粒子的聚合物稳定法和离子液体稳定法。采用透射电镜(TEM)、共聚焦激光扫描显微镜(CLSM)、X射线衍射(XRD)等技术对Pd纳米催化剂进行了表征。三种稳定剂与Pd纳米粒子之间发生物理和化学吸附作用,包裹Pd纳米粒子后,形成了局部的微环境。这种微环境在增溶底物、促进底物与催化剂接触等方面发挥了巨大的作用。因此三种催化体系都体现出催化活性高、选择性好等优点,具有良好的重复使用性。以水或离子液体为反应介质,无论催化剂的制备还是硝基苯的加氢反应都在温和及环境友好的条件下进行。此外,产物与催化剂易分离。该研究为硝基苯催化加氢制备苯胺提供了有效方法,也为其它芳香硝基化合物的催化加氢提供借鉴。
[Abstract]:In this paper, the hydrogenation of nitrobenzene to aniline was studied by using polyvinyl alcohol (PVA) as stabilizer in aqueous PVA-Pd nanometer catalyst for the purpose of environmental friendly and efficient catalysis. PVA-Pd nanoparticles were prepared by hydrogen reduction method in aqueous phase. The average particle size of Pd nanoparticles was 3.2 nm.. Under the optimum conditions, the molar ratio of substrate to catalyst (S / C) 1: 500, temperature 45 掳C, pressure 2 MPa, reaction time 3 h, the conversion of nitrobenzene was 99.30 and the selectivity of aniline was 100. The conversion of nitrobenzene was still over 90% after the catalyst was reused for 4 times. Using triblock copolymer P123 (PEO20-PPO70-PEO20) as stabilizer, the hydrogenation of nitrobenzene to aniline over aqueous phase P123-Pd nano-catalyst was studied. P123-Pd nanocatalysts were prepared by hydrogen reduction method in aqueous phase. The average particle size of Pd nanoparticles was 2.5 nm.. Under the optimum conditions, the molar ratio of substrate to catalyst (S / C) 1: 500, temperature 60 掳C, pressure 3 MPa, reaction time 1 h, the conversion of nitrobenzene was 99.40 and the selectivity of aniline was 100. When the catalyst was reused for 5 times, there was no significant change in activity and selectivity. Based on the double stability of electrostatic steric hindrance of ionic liquids, the hydrogenation of nitrobenzene to aniline over polyether octadecylamine ionic liquid-Pd nanometer catalyst was investigated. The effects of ionic liquid polymerization degree, alkyl chain and anions on the size and morphology of Pd nanoparticles were investigated. Under the optimum conditions, the molar ratio of substrate to catalyst (S / C) is 1: 2000.70 掳C / C, and the reaction time is 3 h at 2 MPa,. The conversion rate of nitrobenzene is 96.05 and the selectivity of aniline is 100. After the catalyst is recycled for 6 times, the conversion rate of nitrobenzene is 96.05 and the selectivity of aniline is 100. There was no obvious change in catalytic activity. The above work includes polymer stabilization method and ionic liquid stabilization method to prepare metal Pd nanoparticles. Pd nanocatalysts were characterized by transmission electron microscope (TEM),) confocal laser scanning microscope (CLSM), X) (XRD) and other techniques. The physical and chemical adsorption between the three stabilizers and Pd nanoparticles resulted in the formation of a local microenvironment after encapsulating the Pd nanoparticles. This microenvironment plays an important role in solubilizing substrates and promoting the contact between substrates and catalysts. Therefore, the three catalytic systems have the advantages of high catalytic activity, good selectivity and good reusability. Using water or ionic liquid as the reaction medium, both the preparation of catalyst and the hydrogenation of nitrobenzene were carried out under mild and environmentally friendly conditions. In addition, the product is easily separated from the catalyst. This study provides an effective method for the hydrogenation of nitrobenzene to aniline, and also provides a reference for the hydrogenation of other aromatic nitro compounds.
【学位授予单位】：青岛科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36
[Abstract]:In this paper, the hydrogenation of nitrobenzene to aniline was studied by using polyvinyl alcohol (PVA) as stabilizer in aqueous PVA-Pd nanometer catalyst for the purpose of environmental friendly and efficient catalysis. PVA-Pd nanoparticles were prepared by hydrogen reduction method in aqueous phase. The average particle size of Pd nanoparticles was 3.2 nm.. Under the optimum conditions, the molar ratio of substrate to catalyst (S / C) 1: 500, temperature 45 掳C, pressure 2 MPa, reaction time 3 h, the conversion of nitrobenzene was 99.30 and the selectivity of aniline was 100. The conversion of nitrobenzene was still over 90% after the catalyst was reused for 4 times. Using triblock copolymer P123 (PEO20-PPO70-PEO20) as stabilizer, the hydrogenation of nitrobenzene to aniline over aqueous phase P123-Pd nano-catalyst was studied. P123-Pd nanocatalysts were prepared by hydrogen reduction method in aqueous phase. The average particle size of Pd nanoparticles was 2.5 nm.. Under the optimum conditions, the molar ratio of substrate to catalyst (S / C) 1: 500, temperature 60 掳C, pressure 3 MPa, reaction time 1 h, the conversion of nitrobenzene was 99.40 and the selectivity of aniline was 100. When the catalyst was reused for 5 times, there was no significant change in activity and selectivity. Based on the double stability of electrostatic steric hindrance of ionic liquids, the hydrogenation of nitrobenzene to aniline over polyether octadecylamine ionic liquid-Pd nanometer catalyst was investigated. The effects of ionic liquid polymerization degree, alkyl chain and anions on the size and morphology of Pd nanoparticles were investigated. Under the optimum conditions, the molar ratio of substrate to catalyst (S / C) is 1: 2000.70 掳C / C, and the reaction time is 3 h at 2 MPa,. The conversion rate of nitrobenzene is 96.05 and the selectivity of aniline is 100. After the catalyst is recycled for 6 times, the conversion rate of nitrobenzene is 96.05 and the selectivity of aniline is 100. There was no obvious change in catalytic activity. The above work includes polymer stabilization method and ionic liquid stabilization method to prepare metal Pd nanoparticles. Pd nanocatalysts were characterized by transmission electron microscope (TEM),) confocal laser scanning microscope (CLSM), X) (XRD) and other techniques. The physical and chemical adsorption between the three stabilizers and Pd nanoparticles resulted in the formation of a local microenvironment after encapsulating the Pd nanoparticles. This microenvironment plays an important role in solubilizing substrates and promoting the contact between substrates and catalysts. Therefore, the three catalytic systems have the advantages of high catalytic activity, good selectivity and good reusability. Using water or ionic liquid as the reaction medium, both the preparation of catalyst and the hydrogenation of nitrobenzene were carried out under mild and environmentally friendly conditions. In addition, the product is easily separated from the catalyst. This study provides an effective method for the hydrogenation of nitrobenzene to aniline, and also provides a reference for the hydrogenation of other aromatic nitro compounds.
【学位授予单位】：青岛科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36
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