N-吡啶联吡唑铱配合物催化氨硼烷水解放氢

发布时间：2018-03-05 21:30

本文选题：氢能源　切入点：氨硼烷　出处：《大连理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：随着世界各国经济的迅猛发展,人类对能源的需求逐渐增大,三大传统化石能源日益枯竭,新能源势必成为未来能源的支柱。清洁能源氢气具有燃烧热值高、不排放任何污染物的特质,是最具发展潜力的新能源。当前,氢气的有效储存是限制氢能源发展的瓶颈。在众多的储氢材料中,氨硼烷质量储氢密度高(19.6 wt%),具有安全无毒、热稳定性和化学稳定性好的特性,拥有非常好的商业应用前景。催化氨硼烷水解制氢以放氢温度适中、放氢量大、环境友好等优点而成为该领域研究的热点。目前多相催化剂存在诸多缺点,例如催化剂用量大、放氢速率慢、副产有毒气体等。相比而言,均相催化剂催化中心分布均匀,在催化活性和选择性方面有极大优势。而有关均相催化的氨硼烷水解制氢研究甚少见诸报道,究其原因在于缺乏稳定高效的水溶性催化剂,因此开发研究高效、高选择性的水溶性均相催化剂对于理解催化氨硼烷水解机制具有重要的学术价值,同时对于推动氨硼烷商业化应用具有重要的现实意义。本文设计合成了四种水溶性良好的N-毗啶联吡唑类铱配合物,并应用于催化氨硼烷水解制氢反应。首先合成了含取代基(Me, MeO, HO)的N-吡啶联吡唑双齿配体。通过这些配体与铱水合物[Cp*Ir(H2O)3]SO4 (Cp*=C5Me5)反应制备了四种水溶性催化剂。随后利用该类催化剂来催化氨硼烷水解放氢。利用[Cp*Ir(6-OH-py-pz)(H2O)]SO4对反应温度、溶液pH值、底物浓度、催化剂用量等条件进行了优化。在确定的最优条件下比较了几种催化剂的活性,结果显示[Cp*Ir(6-OH-py-pz)(H2O)] SO4表现出了最好的催化效果。平均转化频率(TOF)达到360 h-1,1.5小时后所有氨硼烷被彻底水解。在0.3 M氨硼烷条件下9小时后催化水解所有氨硼烷,转化数(TON)达到了1622。[Cp*Ir(6-Me-py-pz)(H2O)] SO4的活性则很低,在加入催化剂0.25小时后才缓慢放氢。[Cp*Ir(4-Me-py-pz)(H2O)] SO4的活性要高于[Cp*Ir(6-Me-py-Pz)(H2O)]SO4,加入催化剂后反应体系立刻放氢。这说明邻位取代甲基的空间位阻作用抑制了催化反应的进行。催化剂[Cp*Ir(6-MeO-py-pz)(H2O)] SO4是所有四种催化剂中活性最低的,放氢实验持续了31小时后,氨硼烷的转化率大约只有50%。结合文献报道和实验结果,本文提出了利用[Cp*Ir(6-OH-py-pz)(H2O)] SO4催化氨硼烷水解放氢的可能机理。其中配体上邻位的羟基增加了催化剂的水溶性。更重要的是碱性条件下生成的氧负离子(0-)和金属中心协同作用,分别与氨硼烷的N-H和B-H形成氢键,从而促进脱氢反应进行,大大提升了催化剂的活性。
[Abstract]:With the rapid development of the world economy, the demand for energy increases gradually, and the three traditional fossil energy sources are increasingly exhausted. The new energy is bound to become the pillar of the future energy. Hydrogen, the clean energy, has a high combustion calorific value. At present, the effective storage of hydrogen is the bottleneck limiting the development of hydrogen energy. Among the numerous hydrogen storage materials, the mass hydrogen storage density of aminoborane is 19.6 wtcm, which is safe and non-toxic. Good thermal and chemical stability, good commercial application prospects. Catalytic hydrolysis of ammonioborane to produce hydrogen at a moderate temperature and large amount of hydrogen, At present, heterogeneous catalysts have many disadvantages, such as large amount of catalyst, slow hydrogen release rate, toxic gas by-product and so on. It has great advantages in catalytic activity and selectivity. However, there are few reports about homogeneous catalytic hydrolysis of aminoborane to produce hydrogen, which is due to the lack of stable and efficient water-soluble catalyst. Highly selective water-soluble homogeneous catalysts are of great academic value in understanding the mechanism of catalytic hydrolysis of aminoborane. At the same time, it is of great practical significance to promote the commercial application of aminoborane. In this paper, we have designed and synthesized four iridium complexes with good water solubility. The N-pyridine-bipyrazole didentate ligands containing substituted groups were first synthesized. Four kinds of water-soluble catalysts were prepared by the reaction of these ligands with iridium hydrate [Cp*Ir(H2O)3] SO4 (CpPX) C5Me5Me5.Then, four kinds of water-soluble catalysts were prepared by the reaction of these ligands with iridium hydrate [Cp*Ir(H2O)3] SO4. This kind of catalyst was used to catalyze the release of hydrogen from ammonioborane in water. The reaction temperature was determined by [CpHIr-6-OH-py-pzOH _ 2O] SO4. The pH value of solution, the concentration of substrate and the amount of catalyst were optimized. The activity of several kinds of catalysts was compared under the determined optimum conditions. The results showed that the SO4 showed the best catalytic effect. The average conversion frequency (TOF) reached 360h-11 (1.5 h) and all the aminoborane was completely hydrolyzed after 9 hours at 0.33M aminoborane, and all aminoborane was hydrolyzed completely after 9 hours under the condition of 0.3m aminoborane. The activity of SO4 is very low. The catalytic activity of SO4 was higher than that of [CpPIR-6-Me-py-Pe-Pzhi-H _ 2O] so _ 4, which indicated that the steric steric inhibition of ortho-substituted methyl inhibited the catalytic reaction. [CpPIr-6-MeO-py-pzni-H _ 2O]. SO4 is the least active of all four catalysts. The hydrogen release experiment lasted for 31 hours, and the conversion rate of aminoborane was only about 50%. In this paper, the possible mechanism of using [CpHIrn 6-OH-py-pznH _ 2O] SO4 to catalyze the release of hydrogen from ammonioborane water is proposed. The water solubility of the catalyst is increased by the ortho hydroxyl group on the ligand, and more importantly, the oxygen anion (0) produced under the basic condition is synergistic with the metal center. Hydrogen bonds were formed with N-H and B-H of aminoborane respectively, which promoted the dehydrogenation reaction and greatly enhanced the activity of the catalyst.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ426;TQ116.2

【共引文献】