【作者】 朱大建；

【导师】 李光兴；

【作者基本信息】 华中科技大学 ， 材料物理与化学， 2009， 博士

【摘要】 Co（Salen）配合物作为一类高效的催化剂,被广泛应用于催化许多有机合成反应,如烯烃不对称催化氧化、环氧化合物水解动力学拆分、烯烃聚合、以及Diels-Alder反应等等。随着人们环保意识的增强和环保法律的强制执行,环境友好和可循环回收利用的高效“绿色”清洁催化剂近年来成为催化领域的研究热点之一,而以无机材料作为载体,将均相催化剂进行负载化是其中一个重要的研究方向。本文首先合成了三种Co（Salen）配合物,并将其用于乙醇氧化羰化合成碳酸二乙酯的反应中,结果发现邻苯二胺桥连的Co（Salophen）较乙二胺和环己二胺桥连的Co（Salen）和Co（Salcyen）的活性要高,Co（Salen）类配合物的量子化学计算结果对此给予了解释,主要是因为Co（Salophen）中Co的电子密度高,有助于底物与钴的配位,进而增强Co（Salophen）的催化活性。同时考察了反应温度、压力、催化剂浓度和时间等反应条件对Co（Salophen）催化剂活性的影响,在优化的条件下,乙醇的转化率可达15.8%,DEC的选择性高于99%。尽管Co（Salen）均相催化体系具有很好的活性,和广泛使用的贵金属相比,也具有一定的经济优势,但在使用中,特别是在氧化羰化反应中易二聚而失活,而均相催化剂的多相化是解决这些问题的有效途径。采用“瓶中造船”的方法,将合成的四种Co（Salen）配合物成功地封装于Y型分子筛的孔道内。采用FT-IR、UV-Vis、BET比表面分析、X射线粉末衍射（XRD）、热分析（TG/DTA）等方法对负载催化剂进行结构表征,证实了钴配合物封装在Y型分子筛的孔道内。将均相和Y型分子筛负载的多相催化剂用于甲醇氧化羰化合成碳酸二甲酯反应,和均相催化剂相比,负载催化剂活性有所增加。原子吸收光谱法确定了负载催化剂中Co含量和反应前后Co的流失量,Co流失实验证实,催化剂中Co含量在循环使用过程中没有明显流失,活性也无明显降低,说明催化剂在反应条件下是稳定和可重复使用的。催化剂腐蚀实验表明Co（Salophen）及Co（Salophen）-Y对不锈钢材质无腐蚀,这对于甲醇氧化羰化反应器的选材是极为有利的。采用循环伏安的方法,研究了Co（Salophen）及Co（Salophen）-Y的电化学行为,提出了与CuCl催化甲醇氧化羰化不同的反应机理。Co（Salophen）与分子氧络合形成超氧物种,然后结合甲醇,CO分子插入,另一分子甲醇亲核进攻,形成碳酸二甲酯。进一步制备了九种Co（Salen）配合物,用于乙二胺氧化羰化反应合成2-咪唑啉酮,结果表明-OH取代的水杨醛与邻苯二胺桥连的Co（Salophen）（OH）₂配合物活性最高,-OH的推电子效应和邻苯二胺苯环的共轭效应共同增加了Co（Salophen）（OH）₂中Co的电子密度,有助于反应物与Co配位活化,提高催化剂的活性。同时考察了反应温度、催化剂用量和时间等反应条件对Co（Salophen）（OH）₂催化剂活性的影响,在优化的条件下,乙二胺的转化率达54.4%,2-咪唑啉酮的产率为49%,提出了Co（Salophen）（OH）₂催化乙二胺氧化羰化的反应机理。总之,Co（Salen）配合物以及分子筛负载的Co（Salen）配合物催化剂对于氧化羰化反应具有高效、环境友好、无腐蚀及能循环回收利用等特点,在有机合成领域将会具有广阔的潜在应用前景。更多还原

【Abstract】 Co(Salen) complexes are widely used as a kind of efficient catalysts in the fields of many organic synthesis reactions, such as asymmetric oxidation of olefin, ring-opening hydrolysis of epoxides, polymerization and Diels-Alder reaction.With the public environment awareness and the compulsive implement of environment legislation, chemists have focused their interest on highly effective, environment friendly and recyclable "green" clean catalysis recently. Among those, homogeneous catalysts immobilized onto inorganic materials are the important research fields.In this work, three kinds of Co(Salen) complexes were synthesized and applied to the oxidative carbonylation of ethanol to diethyl carbonate(DEC). It was found that the activity of Co(Salophen) is higher than that of Co(Salen) and Co(Salcyen), which is rationally explained by the quantum chemistry calculation. The electron density of Co in Co(Salophen) is higher than the other Co complexes, which helps reactants combine with Co and increases the activity of Co(Salophen) catalyst. The reaction conditions, such as temperature, gas pressure, catalyst concentration and reaction time, are also investigated. The conversion of ethanol and the selectivity to DEC in the optimal condition are 15.8% and 99%, respectively.Co(Salen) complexes are active homogeneous catalysts and less expensive compared with noble metal catalysts. However, Co(Salen) complexes are easily prone to formμ-oxo dimmer to lead to lose their activity, especially in the oxidative carbonylation reaction. The heterogeneous catalysis of Co(Salen) complexes is an effective solution to this problem.Four Co(Salen) complexes were successfully encapsulated in the Y zeolite using "ship-in-a-bottle" method. The Co(Salen) complexes encapsulated in Y zeolite are characterized by FT-IR, UV-Vis, BET, XRD and thermal analysis (TG/DTA). The immobilized catalysts and their homogeneous analogues were evaluated in the oxidative carbonylation of methanol to dimethyl carbonate (DMC). Compared with the homogeneous catalysts, the encapsulated Co(Salen) complexes are more active. The content and leaching of Co are determined by atomic absorption spectrometry (AAS). It was found that the Co content in the Co(Salen)-Y and the activity of the catalysts have no change during the reaction, which make sure that the immobilized Co(Salen) complexes were stable and recyclable. The corrosion tests of the catalysts show that Co(Salophen) and Co(Salophen)-Y are noncorrosive to the stainless steel, which is vital to the selection of reactor material in the oxidative carbonylation.The electrochemistry performance of Co(Salophen) and Co(Salophen)-Y was investigated by the cyclic voltammetry (CV). Based on the electrochemistry results, the reaction mechanism of oxidative carbonylation was provided, which was different from the mechanism catalyzed by CuCl system. The mechanism is involved in several steps: Co(Salophen) is first combined with oxygen to form -O-O- species, then combined with methanol, CO insert into the complex, finally another methanol molecule nucleophilic attack reaction to form dimethyl carbonate (DMC).In the further research work, nine Co(Salen) complexes were synthesized to the application of oxidative carbonylation of ethylenediamine to 2-imidazolidinone. It was found that the activity of Co(Salophen)(OH)2 is highest. The -OH substituted salicylaldehyde complexed with o-phenylene diamine help to enhance the electron density of the Co(Salophen)(OH)2. The reaction conditions, such as reaction temperature, catalyst concentration and reaction time, were also studied. The conversion of ethylenediamine and the yield of 2-imidazolidinone at the optimal condition are 54.4% and 49%, respectively. The reaction mechanism of oxidative carbonylation of ethylenediamine catalyzed by Co(Salophen)(OH)2 was provided.In a word, the immobilized Co(Salen) catalysts and their homogeneous analogues are efficient, environmental friendly, noncorrosive and recyclable catalytic systems to oxidative carbonylation reaction, and have wide applications in the fields of organic synthesis.更多还原