基于原子水平的Pd系纳米团簇合成以及催化性质研究

发布时间：2018-07-05 04:20

本文选题：钯 + 团簇　；参考：《安徽大学》2015年硕士论文

【摘要】：贵金属作为珠宝和流通货币,是因为他们不菲的价值和稳定的物理化学性质,所以受到了人们的广泛亲睐。科学家们发现贵金属钯与其它贵金属相比,稳定性高,催化效果好,可以用于催化很多的有机反应。更为重要的是,随着合成方法的改进和单晶衍射技术的发展,科学家们合成了各种各样的原子精确钯团簇,这给钯团簇在催化领域提供了有力的保障。原子精确的金属团簇与普通的金属纳米粒子相比,由于他们的结构确定,可以帮助人们探索催化剂结构与性质之间的关系。本文就在前人的研究基础上,合成单一分散的精确原子钯团簇与合金,应用于催化有机反应,研究催化活性以及在分子原子级水平上探讨催化反应机理。主要内容如下：1.本文通过共还原的方法有效合成一系列组分可控的金钯纳米合金,在这个合成过程中,硼烷叔丁胺化合物作为还原剂,油胺作为溶剂和还原剂对于合成这样一系列的单分散纳米合金有着重要的作用。我们研究这些合金对于苯胺脱氢偶联反应的催化活性,表明合金比等量的单纯Au或Pd的催化效果好。并且Au1Pd3@C在所有合金中表现最好,这表明随着Pd含量的升高转化率和选择性明显升高。但是,如果AuPd合金中Pd的含量太高,比如Au1Pd7@C催化剂,催化效果反而不好(在这个反应中只有81%的转化率)。2.Pd催化Suzuki-Miyaura偶联反应是构建碳骨架最通用且最有利的方法之一然而,由于Pd纳米粒子表面的活性物质和活性位点未知,很难准确的说明为什么Pd纳米粒子可以在有氧的条件下催化Suzuki-Miyaura偶联反应。因此,设计一种原子精确的团簇催化剂在原子水平上研究催化反应的本质十分重要。本文中,我们设计和合成了一个单一活性位点的[Pd3Cl(PPh2)2(PPh3)3]+团簇,然后利用它研究有氧条件下Suzuki-Miyaura偶联反应的反应机理。我们的研究系统的揭示了催化循环过程中的中间体是[Pd3Ar(PPh2)2(PPh3)3]+,这一结果通过质谱、快速X-射线吸收精细结构和密度泛函理论计算分析得到了验证。我们提出来的团簇催化Suzuki-Miyaura偶联反应的反应机理与传统的Suzuki-Miyaura偶联反应的反应机理完全不同。更重要的是,我们的研究将会对更多的金属团簇或者纳米粒子催化C-C偶联反应在反应机理的研究中提供更多的帮助。
[Abstract]:Precious metals as jewelry and currency are popular because of their high value and stable physical and chemical properties. The scientists found that palladium, a precious metal, is more stable and more efficient than other precious metals and can be used to catalyze many organic reactions. More importantly, with the improvement of synthesis method and the development of single crystal diffraction technology, scientists have synthesized a variety of atomic precise palladium clusters, which provides a strong guarantee for palladium clusters in the field of catalysis. Compared with ordinary metal nanoparticles, metal clusters with precise atoms can help to explore the relationship between the structure and properties of catalysts because of their structure determination. On the basis of previous studies, a single dispersed and precise atomic palladium cluster and alloy were synthesized, which were used to catalyze organic reactions, to study catalytic activity and to explore the mechanism of catalytic reactions at the molecular atomic level. The main content is as follows: 1. In this paper, a series of controllable gold and palladium nanocrystalline alloys were synthesized by co-reduction. In this process, borane tert-butylamine compounds were used as reductants. As a solvent and reducing agent, oleamine plays an important role in the synthesis of such a series of monodisperse nanocrystalline alloys. The catalytic activity of these alloys for the dehydrogenation of aniline was studied. Moreover, Au1Pd3 @ C exhibited the best performance in all alloys, which indicated that the conversion and selectivity increased obviously with the increase of PD content. However, if the content of PD in AuPD alloy is too high, such as Au1Pd7@ C catalyst, the catalytic effect is not good (only 81% conversion in this reaction) .2.Pd catalytic Suzuki-Miyaura coupling reaction is one of the most common and advantageous methods to construct carbon skeleton. It is difficult to explain exactly why PD nanoparticles can catalyze Suzuki-Miyaura coupling reaction under aerobic conditions because the active substances and active sites on the surface of PD nanoparticles are unknown. Therefore, it is very important to design a kind of atom precise cluster catalyst to study the nature of catalytic reaction at atomic level. In this paper, we designed and synthesized a single active site [Pd3Cl (PPh2) 2 (PPh3) 3] cluster, and then used it to study the reaction mechanism of Suzuki-Miyaura coupling under aerobic conditions. Our study systematically revealed that the intermediate in the catalytic cycle was [PD _ 3Ar (PPh2) _ 2 (PPh3) _ 3], which was verified by mass spectrometry, fast X-ray absorption fine structure and density functional theory calculation. The reaction mechanism of the cluster catalyzed Suzuki-Miyaura coupling reaction is completely different from that of the traditional Suzuki-Miyaura coupling reaction. More importantly, our research will provide more help in the study of the reaction mechanism of C-C coupling reaction catalyzed by more metal clusters or nanoparticles.
【学位授予单位】：安徽大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1;O614.823

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