温控自分离纳米金催化剂在醇类的选择性氧化中的应用

发布时间：2018-04-04 11:27

  本文选题：温控自分离　切入点：纳米金催化剂　出处：《湖南师范大学》2015年硕士论文

【摘要】：纳米金催化剂在醇类选择性氧化反应中有很好的催化性能,是目前纳米金催化领域的研究热点。近年来,溶胶型纳米金催化剂作为拟均相纳米金催化剂受到了广泛关注。该类催化剂中的纳米金活性中心能与反应底物充分接触,因而在液相选择性氧化反应中展示出很高的催化效率。由于溶胶型纳米金催化剂采用有机化合物作为金纳米粒子稳定剂,常存在催化剂难以分离,回收使用困难的问题。任务导向型离子复合物的阴阳离子结构可以根据特定需要进行功能化修饰,同时,离子复合物表面张力很低,能很好的稳定纳米粒子,因而以其作为溶胶型纳米金催化剂的稳定剂,有可能解决催化剂的分离问题。本论文在前期研究结果的基础上,以聚乙二醇(PEG)修饰任务导向型离子复合物,利用PEG在甲苯中的特殊温控相变性能,得到具有温控自分离特性的溶胶型拟均相纳米金催化剂,并考察了其在醇类选择性氧化中的催化性能,具体工作如下:(1)选取PEG6000合成了氯离子为阴离子的乙烯基功能化离子复合物[PEG6000VIM][Cl],通过阴离子交换反应,将乙酸根阴离子引入其中,合成了乙酸根为阴离子的乙烯基功能化离子复合物[PEG6000VIM][Ac]。分别以上述两种离子复合物作为稳定剂制备了相对应的纳米金催化剂[PEG6000VIM][Cl]-GNPs和[PEG6000VIM][Ac]-GNPs。以分子氧为氧化剂,考察了两种催化剂在无碱条件下苯甲醇选择性氧化反应中的催化性能,相比于含氯离子的催化剂[PEG6000VIM][Cl]-GNPs及文献中纳米金催化的同类反应,含乙酸根的离子复合物稳定的纳米金催化剂[PEG6000VIM][Ac]-GNPs表现出大为提高的TOF值。优选了金含量为0.065wt%的[PEG6000VIM][Ac]-GNPs-0.065作为最佳催化剂,考察了溶剂甲苯的用量、反应温度、催化剂用量及反应时间对苯甲醇选择性氧化反应的影响,在最佳反应条件下,催化剂的TOF值达到了0.63 mol·g-1·h-1。(2)为提高苯甲醇的转化率,引入了第二种金属到催化剂[PEG6000VIM][Ac]-GNPs中,制备了常见的金基双金属催化剂Au-Cu/[PEG6000VIM][Ac]、Au-Ag/[PEG6000VIM][Ac]、Au-Mn/[PEG6000VIM][Ac]、Au-Pd/[PEG6000VIM][Ac],从中优选了催化剂Au-Pd/[PEG6000VIM][Ac]。对催化剂中Au-Pd含量及组成结构进行了优化,得到了最佳催化剂Au1Pd7/[PEG6000VIM][Ac]-0.6:Au-Pd摩尔比为1:7,Au与Pd总金属含量为0.6 wt%。在最佳反应条件下,该催化剂的苯甲醇转化率和苯甲醛选择性分别达到98.3%和99.0%。
[Abstract]:Nanocrystalline gold catalysts have good catalytic performance in the selective oxidation of alcohols.In recent years, sol-type nanocrystalline gold catalysts as pseudo-homogeneous nanocrystalline gold catalysts have attracted wide attention.The nanometer gold active center in this kind of catalyst can fully contact with the substrate, so it shows high catalytic efficiency in the liquid phase selective oxidation reaction.Due to the use of organic compounds as stabilizers of gold nanoparticles in sol-type nanocrystalline gold catalysts, it is often difficult to separate the catalysts and recycle them.The cationic and anion structures of task-oriented ionic complexes can be functionalized according to specific needs. At the same time, the surface tension of ion complexes is very low and the nanoparticles can be well stabilized.Therefore, it is possible to solve the problem of catalyst separation by using it as a stabilizer of sol-type nano-gold catalyst.Based on the previous research results, the task-oriented ionic complexes were modified with polyethylene glycol (PEG), and the sol-like pseudo-homogeneous nano-gold catalysts with temperature control self-separation properties were obtained by using the special temperature-controlled phase transition of PEG in toluene.Its catalytic performance in selective oxidation of alcohols was also investigated. The main work was as follows: (1) PEG6000 was selected to synthesize vinyl functionalized ion complex [PEG6000VIM] [Cl] with chloride ion as anion, and the acetate anion was introduced into it by anion exchange reaction.Vinyl functionalized ionic complex [PEG6000VIM] [ac] with acetate as anion was synthesized.The corresponding nanocrystalline gold catalysts [PEG6000VIM] [Cl] -GNPs and [PEG6000VIM] [ac] -GNPs were prepared by using the above two ionic complexes as stabilizers, respectively.The catalytic properties of two catalysts for selective oxidation of benzyl alcohol under alkali-free conditions were investigated by using molecular oxygen as oxidant. Compared with the catalyst [PEG6000VIM] [Cl] -GNPs containing chlorine ion and the similar reactions catalyzed by gold nanoparticles in literature, the catalytic performance of the two catalysts was compared with that of the catalyst [PEG6000VIM] [Cl] -GNPs containing chloride ions.The [PEG6000VIM] [ac] -GNPs prepared by ionic complex containing acetic acid showed a significant increase in TOF value, and the gold nanocrystalline catalyst [PEG6000VIM] [ac] -GNPs showed a significant increase in TOF value.[PEG6000VIM] [ac] -GNPs-0.065 with gold content of 0.065 wt% was selected as the best catalyst. The effects of the amount of toluene, reaction temperature, catalyst amount and reaction time on the selective oxidation of benzyl alcohol were investigated.鍌�鍖栧墏鐨凾OF鍊艰揪鍒颁簡0.63 mol路g-1路h-1.(2)涓烘彁楂樿嫰鐢查唶鐨勮浆鍖栫巼,寮曞叆浜嗙��浜岀�嶉噾灞炲埌鍌�鍖栧墏[PEG6000VIM][Ac]-GNPs涓，

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