【作者】 郭丽萍；

【导师】 李浩然； 王从敏；

【作者基本信息】 浙江大学 ， 化学， 2010， 博士

【摘要】 随着地球资源日趋匮乏和环境问题日趋严重,如何将CO2变废为宝是当今世界的焦点之一。利用环氧化合物和CO2反应,生成相应的工业原料聚碳酸酯或环碳酸酯是目前化学固定C02研究领域的热点。在众多催化体系中,(salen)MX催化体系对空气和水稳定,催化剂合成较简单,催化效率较高,因而具有良好的工业应用前景,是近十年来C02共聚及环加成反应领域最受瞩目的催化体系之一。季铵(鏻)盐等助催化剂的加入,能大幅度提高该催化体系的催化活性和反应的选择性。虽然经过近十年的研究,该催化体系已有了很大的发展,但是由于其在该领域的应用时间不长,其相关反应机理以及新催化剂的开发都有待进一步的研究。本论文以(salen)MX-季铵(鏻)盐催化体系为主要研究对象,合成了几类新型(salen)MX配合物,并考察了其在催化环氧化合物和CO2反应中的效果,此外,我们还单独对助催化剂季铵(鳞)盐在该类反应中的催化活性进行了较细致的研究。目前salen催化剂的二胺骨架主要集中于环已二胺、苯二胺、乙二胺等邻位二胺,而以非邻二胺型salen金属配合物催化二氧化碳和环氧化合物的共聚反应鲜有报道。本论文在第二章中以天然赖氨酸为二胺骨架,首次合成了非邻二胺骨架的赖氨酸型salen金属铬配合物(lys-salen)CrCl,并将其应用于二氧化碳和环氧化合物共聚反应中。实验结果表明,(lys-salen)CrCl结合助催化剂双三苯基膦氯化铵(PPNC1),能有效催化CO2和环氧环已烷(CHO)的交替活性共聚。与传统的(salen)MX催化剂相比,该催化剂的优点在于它是由市售的环保的天然赖氨酸为原料合成的,并且,虽然其催化活性并没有比传统(salen)MX有明显提高,但是(lys-salen)CrCl显示了更好的稳定型：共聚反应的选择性和聚合产物的聚碳酸酯链节含量不易受反应环境影响,始终保持在很高的水平。此外,对(lys-salen)CrCl的ESI-MS表征发现,一分子水紧密结合在配合物金属中心上,这为“金属中心上结合的水引起了产物分子量的双峰分布”提供了直接的证据。在第三章中,我们将(lys-salen)CrCl-PPNCl用于催化CO2和另一种单体环氧丙烷(PO)的反应,结果表明,该催化体系也能在较低的催化剂浓度下,使CO2和PO进行环合反应生成相应的环碳酸酯。由于催化CO2和PO共聚反应的多为salen金属钴配合物,我们又合成了(lys-salen)CoOAc,并考察了其在催化CO2和PO反应中的效果,结果表明,(lys-salen)CoOAc-PPNCl催化体系中CO2和PO发生的是环合反应。多个研究表明,离子液体支载型化合物在催化领域具有特殊的优越性。如果将季铵(鏻)盐助催化剂直接支载在主催化剂(salen)MX中,这种双功能型催化剂能不能在CO2和环氧化合物的反应中发挥特殊的作用呢?第四章中,我们尝试在salen配体的苯环上进行改造,合成季铵盐支载型salen金属配合物,并最终成功合成了几种咪唑盐支载的salen金属配合物。催化反应结果表明,只有小部分金属配合物能催化PO和CO2的环合反应,大部分配合物没有明显的催化效果。经过对比和分析,我们认为低溶解度和支载链太短可能是催化剂失活的两个重要因素,为以后开展相似的工作提供了参考。催化剂(salen)MX的结构可以多变,而助催化剂季铵(鏻)盐的种类也非常繁多。目前,催化剂的优劣大多数是通过实验操作,根据各体系催化反应的结果进行比较得出的。然而,这种挑选催化剂的方法会耗费比较多的人力、物力以及能源。因此,从保护资源的角度看来,如何更简单、更经济地选择催化体系也是一个重要的议题。在第五章中,我们以季铵(鳞)盐和碱金属盐等卤化盐为对象,研究了它们在水辅助催化CO2和PO的反应中,反应活性和电导率之间的关系。结果表明,无论是催化剂改变、水量改变还是助溶剂改变时,反应活性的变化趋势和电导率的变化趋势是基本一致的。这不仅用实验直接证实了在CO2和环氧化合物反应体系中,季铵(鳞)盐等催化剂的活性与其离子的移动能力密切相关；更重要的是,这一现象提示我们,在这类反应,甚至于其他由卤化盐催化的反应中,也许可以通过进行简单的电导率测量来初步筛选催化体系。总体来说,本论文主要在环氧化合物化学固定CO2领域,以(salen)MX-季铵(鏻)盐催化体系为研究对象,对(salen)MX的设计与合成和季铵(鏻)盐的催化作用等方面进行了探索和研究,为该催化体系的设计和改进提供了经验。更多还原

【Abstract】 Carbon dioxide fixation has received worldwide attention in decades, since CO2 is not only one of the greenhouse gases, but also an abundant, economical, and biorenewable resource. One of the most promising reactions in this area is the reaction of CO2 and epoxides to prepare polymeric or cyclic carbonates. Since salen-metal complexes [(salen)MX] are stable to air and water, easy to prepare, and have higher catalytic activity for the copolymerization of CO2 and epoxides, among the numerous metal-based catalyst systems, the salen-metal complex system is of special interest. Using binary catalyst system of (salen)MX as catalyst in conjunction quaternary ammonium/phosphonium salt cocatalyst could markedly enhance the catalytic activity and selectivity. However, it has been only about ten years since salen-metal complex was firstly applied to catalyze the reaction of CO2 and epoxides. Therefore, while some achievements have been made in this area, there are still many areas we need to explore, such as the modification and development of (salen)MX or investigating the reaction mechanism in more detail, In this paper, we focus on the (salen)MX- quaternary ammonium/phosphonium salt catalytic system. Several new salen metal complexes are synthesized and applied to catalyze the reaction of the CO2 and eopxides. In addition, the catalytic activity of the quaternary ammonium/phosphonium salts on such reaction is studied in more detail.Up to now, diamines, as the framework for H2salen ligands, focus only on some ortho-diamines, such as 1,2-cyclohexenediamine,1,2-phenylenediamine, and 1,2-ethylenediamine. So far as we know, the copolymerization catalyzed by salen-metal complex from non-ortho-diamine was absent. It prompted us to verify whether the salen-metal complex synthesized from non-ortho-diamine could effectively catalyze the copolymerization of CO2 and epoxides. We prepared a natural lysine-based (salen)CrⅢCl, and investigated the copolymerization of CO2 and cyclohexene oxide(CHO) catalyzed by this catalyst. The results showed that the (lys-salen)CrⅢCl, with PPNC1 (PPN+=bis(triphenylphosphoranylidene)ammonium) as cocatalyst, could effectively catalyze the alternating copolymerization. In contrast to the traditional salen-metal catalysts, the (lys-salen)CrⅢCl catalyst was prepared from lysine, which is commercially available and optically pure. Although the activity of (lys-salen)CrⅢCl catalyst is not better than traditional salen-metal catalysts, it shows some advantages such as high carbonate linkage, narrow molecular weight distribution, and good selectivity. In addition, the ESI-MS measurement of (lys-salen)CrⅢCl indicated that one molecule of water coordinated to the central metal ion, responding to the bimodal GPC curve of copolymers.The catalytic activity of (lys-salen)CrⅢCl-PPNCl on the reaction of CO2 and propylene oxide(PO) was also investigated, and it exhibited that this catalytic system could catalyze the coupling reaction of CO2 and PO in low catalytic concentration, producing cyclic carbonate. Since the copolymerization of CO2 and PO is usually catalyzed by salen cobalt complexes, the cobalt complex of lys-salen ligand [(lys-salen)CoOAc] was also prepared and applied to catalyze the reaction of CO2 and PO. It is a pity that it is also a coupling reaction between CO2 and PO.Many studies show that the ionic-liquid-supported catalysts are of particular advantage in many reactions. Can we synthesize a quaternary ammonium/phosphonium-supported salen metal complex? Is such a bifunctional salen metal catalyst of particular advantage in the reaction of CO2 and epoxides? We tried to modify the phenyl of salen ligand, in order to prepare quaternary ammonium-supported salen metal complex, and finally several ammonium-supported salen metal complexes were synthesized. However, most of these complexes have almost no catalytic activity. We believe that low solubility in PO and the short distance between the supported ammonium and metal center are main factors for the deactivation of catalysts.In most cases, a better catalyst is selected by comparing the reaction results with different catalysts after practical experiment. From the standpoint of resource conservation, how to select catalysts simply and cost-effectively is also an important topic. The relationship of activity and electrical conductivity of catalyst, which contains quaternary ammonium/phosphonium and alkali halides, in water-assisted coupling reaction of CO2 and PO was studied. It exhibited that the PO conversion was closely correlated with the electrical conductivity, when different catalysts, different amounts of water, and different hydroxy solvents were added in the reaction. This phenomenon not only proves that the catalytic activity was closely related to the ionic mobility of catalysts, but also indicates the simple operation of conductivity measurement might be helpful in deciding which catalyst should be chosen, which solvent should be used, how much solvent should be added in these reactions, and even in some other halide salts-aided reaction.To sum up, several new salen metal complexes were synthesised, and combined with quaternary ammonium/phosphonium salts, which were applied to catalyze the reaction of CO2 and epoxide. In addition, the activity of quaternary ammonium/phosphonium salt was studied. We except it can be used for the futher development of the (salen)MX-quaternary ammonium/phosphonium salt catalytic system for the chemical fixation of CO2.更多还原