SPG乳化法制备微胶囊负载钯催化剂及性能研究

发布时间：2018-02-08 20:53

  本文关键词： SPG乳化法 微胶囊负载钯催化剂 碳-碳键形成　出处：《大连理工大学》2010年博士论文　论文类型：学位论文

【摘要】： 均相配位催化普遍具有反应效率高、选择性好、反应条件温和等优点,在现代有机合成中占有重要的地位。但是,均相配位催化存在催化剂与产物难以分离、催化剂的回收和再利用困难等问题。为了解决这些问题,化学研究者们制备了负载型的过渡金属催化剂,载体包括MCM-41、SBA-15等无机材料,以及有机高分子材料。这种方法虽然结合了多相催化与均相催化的优点,有些催化剂表现出较高催化活性和选择性,但由于金属配合物多被负载于载体表面,且金属—配体之间通常是通过较弱的配位键相结合,不可避免发生金属活性物种向反应液的溶出,使得催化活性降低；又由于这种负载型的催化剂不能较好地分散于反应介质中,影响了催化反应效率,反应时间通常比均相催化长。微胶囊负载过渡金属配合物是一种新型的有机高分子负载型催化剂,可均匀分散于整个反应介质中,其膜内配体的多点可配位作用,将更有效地阻止活性物种的流失。 本论文通过改进的方法,合成了4-二苯基膦苯乙烯(SDPP) 45单体,并利用SPG膜乳化技术制备了粒径分布均匀、膜内连有膦配体的微胶囊。最佳制备条件是：以含SDPP 1.20 g、20 wt%二乙烯基苯(DVB)和3.0 wt%的偶氮二异丁基腈(AIBN)的甲苯溶液作为分散相,以含1.0wt%的聚乙烯醇(PVA)和0.30 g／L的十二烷基硫酸钠(SLS)的水溶液作为连续相,70℃下聚合反应24 h。通过配体交换反应,获得微胶囊膜内负载钯催化剂,并利用电感偶合等离子体发射光谱分析(ICP)测定了钯含量。利用光学显微镜、扫描电子显微镜(SEM)和透射式电子显微镜(TEM)等对微胶囊及其负载钯催化剂的结构进行了表征。 通过微胶囊负载钯催化的Suzuki交叉偶联反应,考察了其催化性能及稳定性。在最佳反应条件下(1.0mol%Pd、卤代芳烃0.25 mmol,芳基硼酸0.38 mmol, K2CO30.38 mmol, IPA 2mL,80℃),溴代芳烃与苯硼酸的反应产率在80%以上,最高可达到99%。催化剂重复使用11次,4-溴苯乙酮与苯硼酸的反应产率仍可达到96%。 研究结果表明,所制得的微胶囊负载钯催化剂还能催化碘代芳烃与丙烯酸甲酯参与的Heck反应,反应产率为51-99%。催化剂经简单过滤后,重复使用5次,依然保持活性基本不变,碘苯与丙烯酸甲酯的反应产率保持在91%以上。 三相试验研究结果表明,微胶囊负载钯催化溴代芳烃与苯硼酸的Suzuki交叉偶联反应,可认为催化反应是在微胶囊内部进行的,即反应物通过微胶囊的膜孔道进入其内部,在钯催化剂的作用下,转化成产物后,再经膜孔道离开微胶囊。
[Abstract]:Homogeneous coordination catalysis has many advantages, such as high reaction efficiency, good selectivity, mild reaction conditions and so on, and plays an important role in modern organic synthesis. In order to solve these problems, the chemical researchers have prepared supported transition metal catalysts, which include inorganic materials such as MCM-41, SBA-15 and so on. Although this method combines the advantages of heterogeneous catalysis and homogeneous catalysis, some catalysts exhibit high catalytic activity and selectivity, but the metal complexes are mostly supported on the surface of the support. And the combination of metal and ligand is usually through the weak coordination bond, which inevitably leads to the dissolution of metal active species to the reaction solution, which results in the decrease of catalytic activity. Because this kind of supported catalyst can not be dispersed in the reaction medium well, it affects the efficiency of catalytic reaction. The reaction time is usually longer than that of homogeneous catalysis. Microencapsulated transition metal complexes are novel organic polymeric supported catalysts, which can be uniformly dispersed in the whole reaction medium. It will be more effective in preventing the loss of active species. In this paper, 4- diphenylphosphine styrene (SDPP) 45 monomer was synthesized by improved method, and the particle size distribution was uniform by SPG membrane emulsification technology. The optimum preparation conditions were as follows: toluene solution containing SDPP 1.20 g ~ (-1) W ~ (20) w ~ (t) divinylbenzene (DVB) and 3.0 wt ~ (%) azo-diisobutyl nitrile (AIBN) as dispersion phase. The aqueous solution containing 1.0 wt% polyvinyl alcohol (PVA) and 0.30 g / L sodium 12 alkyl sulfate (SLS) was polymerized at 70 鈩，

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