【作者】 蒋成君；

【导师】 陈志荣； 李浩然；

【作者基本信息】 浙江大学 ， 化学工程与技术， 2009， 博士

【摘要】 论文首先采用了一套简单有效的方法用于水解动力学拆分催化剂的设计过程。在该方法的指导下,发现了水解动力学拆分催化剂结构与活性的关系,提出了用异核双金属催化剂来提高水解动力学拆分末端环氧化合物催化活性的方案。然后设计并合成了一类全新、廉价、高效的水解动力学拆分异核双金属催化剂。研究结果表明,与传统催化剂相比,这类催化剂的活性明显提高。论文进一步将此异核双金属催化剂固载在天然大分子化合物-壳聚糖上,使其具有易回收的优点,有利于过程绿色化。论文的目的并不局限于新型催化剂的制备和应用这两个方面,如何采用合理的模型、可行的方法来高效、准确地对催化剂进行设计将是更具推广及借鉴意义的内容。因此本论文首先提出问题:用于水解动力学拆分的（salen）Co（Ⅲ）（OAc）催化剂在反应中为什么会失活?是何种因素影响了水解动力学拆分催化剂的活性?水解动力学拆分催化剂结构与性能存在着何种关系?是否存在活性更高的催化剂?能否将均相的水解动力学拆分催化剂固载化?以上问题的回答是通过四个部分的研究逐步得出的:（1）（salen）Co（Ⅲ）（OAc）在水解动力学拆分过程中失活机理的研究;（2）单核（salen）Co（Ⅲ）催化剂结构与活性关系的研究;（3）异核双金属催化剂的合成及应用研究;（4）壳聚糖固载异核双金属催化剂的合成及应用研究。第一部分是（salen）Co（Ⅲ）（OAc）在水解动力学拆分中失活机理的研究。论文采用紫外分光光度、红外光谱等方法对催化剂和催化过程进行研究,采用GC-MS对产物进行分析,认为催化剂与水反应生成了（salen）Co（Ⅲ）（OH）,（salen）Co（Ⅲ）OAc+H₂O→（salen）Co（Ⅲ）（OH）+HOAc,（salen）Co（Ⅲ）（OH）在反应过程中的不断累积是引起催化剂失活的主要原因。第二部分是单核（salen）Co（Ⅲ）催化剂结构与活性关系的研究。论文首先对含不同轴向阴离子配体的（salen）Co配合物进行了一些理论研究。应HYPERCHEM软件,采用量子化学中的PM3方法对催化剂的E_HOMO、E_LUMO、催化剂的活性中心钴的电荷以及催化剂的总能量进行计算。与文献报道的数据对比分析,结果表明:催化剂的活性与催化剂的前线分子轨道能量有一定的关系,但是并不是表征供电子能力的最高被电子占有分子轨道（HOMO）和表征接受电子能力的最低空分子轨道（LUMO）的高低与催化剂的活性直接相关,LUMO与HOMO能级差ΔE_L-H决定催化剂反应活性的高低,ΔE值越大,催化剂活性越弱,而具有较小的ΔE_L-H的催化剂,活性较高。这可能是因为（salen）Co催化剂活化环氧化合物时,需要在轨道相互作用时达到一个平衡的状态,即催化剂即要能与环氧化合物络合,又要能在后续反应时容易脱离。因此催化剂的HOMO或者LUMO太高或太低都不利于催化的整个过程。催化剂的反应速率常数K和ΔE_L-H有很好的相关性,K^*10³=27.8-3.12ΔE_L-H,相关系数R=0.97。在以上研究的基础上,首先通过结构类似的新型催化剂验证了所提出的观点。在这些结构类似的催化剂中,以CF₃COO^-为轴向阴离子时催化剂的活性最高。当其用量为0.5mol%,水用量为0.55当量的条件下,反应进行8小时,产物ee值可达到99%。在得到验证的同时,本论文预测了一类与传统催化剂相比,催化活性更高的异核双金属催化剂。第三部分是异核双金属催化剂的合成和应用。采用预期能够提高催化剂催化活性的修饰方式,合成了系列异核双金属催化剂。采用等离子发射光谱、红外光谱及元素分析对这些异核双金属催化剂进行了表征。将催化剂应用于水解动力学拆分末端环氧化合物。研究发现在温度为20℃,催化剂的用量为0.25mol%,水用量为0.55当量的条件下,异核双金属催化剂（salen）Co（Ⅱ）（ZnCl₂）、（salen）Co（Ⅱ）（FeCl₃）、（salen）Co（Ⅱ）（SnCl₄）、（salen）Co（Ⅱ）（AlCl₃）的活性高于（salen）Co（Ⅲ）OAc,反应进行10小时,产物ee值可达到99%。异核双金属催化剂比（salen）Co（Ⅲ）OAc具有更高的催化活性。这可能是因为同一个salen单元的钴活化末端环氧化合物,另外一个活性中心活化水,即可以发生同一催化剂单元内的反应也可以发生不同催化剂单元间的反应,从而提高催化剂的活性。在同一个催化剂单元发生如下反应:被其他金属活化的水进攻与钴相连的环氧化合物,形成一个过渡态,过渡态与水反应迅速生成二醇和催化剂,催化剂进入下一个循环中。在实验中发现了异核双金属催化剂的非线性效应,用Kagan提出的非线性效应（+NLE）简化数学模型拟合所得的数据,相关系数R=0.98。第四部分是将异核双金属催化剂固载在壳聚糖上,研究目的在于有利于反应的后处理、催化剂的回收利用,将催化剂应用于环氧氯丙烷的水解动力学拆分。研究结果表明:各种固载双核salen催化剂都显示了较优越的催化效果,反应10小时,（S）-环氧氯丙烷的ee值都能够达到99%。本课题来源于生产实际,所得的结果优于早期的发现,尤其是涉及如何采用合理的模型以提高设计效率和准确率等问题,采用的方法及得到的结论具有一定的通用性,为其他催化剂的设计提供了可供参考的新思路和新方法。更多还原

【Abstract】 A simple and reasonable method to design the hydrolytic kinetic resolution （HKR） catalysts with high efficiency was developed.Guided by this method,the structure-reactivity relation of HKR catalysts was found and heteronuclear bimetallic catalysts were proposed to enhance the catalytic activity of traditional catalysts.Based on this,a new kind of cheap and high effective HKR catalysts were designed and synthesized,which could overcome the poor activity of traditional catalysts, furthermore,chitosan supported heteronuclear bimetallic catalysts were designed, which were easy to recover.The purpose of this thesis was not limited to prepare and apply the new catalysts. How to construct a reasonable model and develop a feasible method to design the catalysts accurately and effectively was also studied.Several questions were proposed in this thesis:Why does the Jacobsen’s Co-salen catalyst deactivate in HKR? What will affect the activity of catalyst? What’s the relationship between the structure and performance of the catalysts? Is there any catalyst with more activity? Can the catalyst be loaded homogeneously?All of above questions were concluded step by step in four research sections, which are listed as follows:（1） the mechanism of deactivation of Jacobsen’s Co-salen catalyst during the HKR;（2） relationship between the structure and performance of the catalysts; （3）synthesis and apply the new heteronuclear bimetallic catalysts;（4） synthesis and apply new loading heteronuclear bimetallic catalysts.The first part of the thesis concerned the mechanism of deactivation of Jacobsen’s catalysts.Possible mechanisms of deactivation of Jacobsen’s Co-salen catalyst during the HKR of epichlorohydrin were explored by UV-vis spectroscopy, IR spectroscopy and GC-MS.It indicated that the main reason was the addition of the Co-salen counterions to epoxide the formation of Co-OH during the reaction correlated with deactivation.（salen）Co（Ⅲ）OAc+H₂O→（salen）Co（Ⅲ）（OH）+HOAc. The deactivation also could be attributed to the destroy of complexation structure.The second part of the thesis concerned the relationship between the structure and performance of the catalysts.Some fundamental research were put forward to the （salen）Co containing different anionic axial ligands.The geometric structures,E_HOMO, E_LUMO,electron densities of cobalt and energy are calculated at PM3 level.Compared to the results reported in literature,the structure-reactivity relation of HKR catalysts was found and a method to enhance the catalytic ability of HKR catalysts was proposed.A new kind of high effective catalysts were designed.The factors affect catalytic activity directly were not the HOMO and the LUMO.The center cobalt atom of （salen）Co（Ⅲ） activated the epoxy compounds and epoxy compounds broke at the same time.ΔE_L-H(Energy level difference of E_LUMO and E_HOMO) determined the activity of catalyst.This could be owned to the adsorption and desorption on the active center-cobalt.The relationship of theΔE_L-H and speed constant was K^*10³=27.8-3.12ΔE_L-H,and the related coefficient R for regression was 0.97.At the same time,some catalysts containing different axial direction anionic ligands were applied in HKR of racemic terminal epoxides.Reliability of the catalyst design was verified.At 20℃,with the water equivalent of 0.55,and the catalyst concentration of 0.5mol%,the e.e.of the（S）-epichlorohydrin would reach 99%in 8 hr catalyzed by the new or the reused（salen）Co（Ⅲ）（OOCF₃）.The third part of the thesis concerned the synthesis and application of heteronuclear bimetallic catalysts.The synthesized heteronuclear bimetallic catalysts were expected to improve the reactivity.This kind of new catalysts was explored by UV-vis spectroscopy,IR spectroscopy,elementary analysis and ICP.Validity of the catalysts were inspected and verified by the application in HKR of racemic terminal epoxides.At 20℃,with the water equivalent of 0.55,and the catalyst concentration of 0.25mol%,the activity of（salen）Co（Ⅱ）（ZnCl₂）,（salen）Co（Ⅱ）（FeCl₃）, （salen）Co（Ⅱ）（SnCl₄）,and（salen）Co（Ⅱ）（AlCl₃）was better than that of （salen）Co（Ⅲ）OAc,and the e.e.of the（S）-epichlorohydrin could reach 99.5%in 10 hr.The activity of heteronuclear bimetallic catalysts were higher than that of the （salen）Co（Ⅲ）OAc.The reason could be that the cobalt activated epoxy compounds in one salen unit and other active center may active the water,and the reaction may take place in one unit or two,and then the activity of catalyst may be improved.The water connected on the other metals could attack the activatory epoxy compounds to form a transient formation,which could react with water quickly to form water and diol.Nonlinear effects of the heteronuclear bimetallic catalysts were discovered in the experiments,and the mathematical model of（+NLE） proposed by Kagan were used to fit the results.The fourth part of the thesis concerned the preparation of chitosan-supported chiral salen Co（Ⅱ） catalyst and its application in HKR of epichlorohydrine.Chitosan supported（salen）Co（Ⅱ） with different anionic ligand were synthesized.The ligand and catalyst were characterized by NMR,IR spectroscopy,elemental analysis and ICP.The catalystes were then used for HKR of ECH.The results showed that in respect of catalytic effect,the ZnCl₂,AlCl₃,FeCl₃,and SnCl₄ as anionic ligand was better,and the e.e.of the（S）-epichlorohydrin could reach 99%in 10 hr.This project comes from the industry and the obtained results are preponderant, compared to some of the previous methods.It provides more choices for the industry. This thesis deals with both the experiments and theories.Especially,it concerns how to build reasonable models to enhance the accuracy and efficiency of the design process.The methods used in this thesis are universal.It provides some feasible methods and ideas for the catalyst designing process.更多还原