磁性纳米催化剂的制备、表征及其在Knoevenagel缩合反应中的应用研究

发布时间：2018-01-26 04:52

本文关键词： 磁性纳米材料纳米催化剂 Knoevenagel缩合反应磁性分离循环利用　出处：《浙江大学》2016年硕士论文　论文类型：学位论文

【摘要】：磁性纳米材料具有特殊的物理性质和化学性质,在电子、信息、自动控制、有机合成、生物医药等学科领域有广泛的应用。特别是对于催化领域,磁性纳米粒子作为催化剂或催化剂载体表现出优异的性能,且它还具有可磁性分离的特性,为纳米级催化剂的分离提供了新的思路。Knoevenagel缩合反应是形成C=C最重要的反应之一,其缩合产物是极其有价值的合成中间体,在化工领域占据非常重要的地位。因此,拓展磁性纳米材料的应用范围,使其作为绿色,环保的催化剂用于Knoevenagel缩合反应的研究,不仅具有基础研究的创新性,也具有重要的工业化应用意义。本文主要从以下两个方面对磁性纳米材料作为Knoevenagel反应的催化剂进行研究。一方面,通过溶剂热法和Stober法分两步制备出Fe3O4@SiO2磁性纳米催化剂,采用FTIR、XRD、TEM、VSM等手段确定其结构和组成。以苯甲醛与丙二腈的Knoevenagel缩合作为探针反应,并优化反应条件,在最佳条件下实现苯甲醛的完全转化后,目标产物的收率达到97.8%。同时,通过对比不同催化剂的实验结果,推断Fe3O4@SiO2催化剂的活性组分为Si02层。循环实验表明Fe3O4@SiO2催化剂循环使用第7次时仍然能维持90.1%的转化率和93.5%的选择性,且催化剂的结构和组成在重复利用中也没有发生改变。因此,所制备的催化剂具有优异的可循环利用性和稳定性。而且,Fe3O4@SiO2磁性纳米催化剂可通过外加磁场进行分离,操作简便,具有很好的工业化应用前景。此外,将Fe3O4@SiO2运用在11种不同结构的醛与丙二腈反应中。结果表明,大部分的反应在催化剂的作用下能较快进行,且底物中吸电子基以及苯环的存在对反应效果有积极的作用。另一方面,本文采用一步溶剂热法制备了一系列MFe2O4(M=Mn,Cu,Co, Zn和Ni)磁性纳米粒子,通过FTIR、XRD、TEM、BET、VSM等手段确定其结构和组成。同样以苯甲醛与丙二腈的Knoevenagel缩合作为模型反应,考查不同MFe2O4纳米粒子对反应的催化效果,结果表明NiFe2O4催化活性最好,同时推断M元素为MFe2O4的关键活性组分。优化NiFe2O4催化剂用量使得目标产物收率高达98.6%。通过在最佳条件下的循环实验,发现NiFe2O4循环使用第8次时活性没有明显降低仍然能维持反应95.1%的转化率和96.2%的选择性,且催化剂的结构和组成在重复利用中也没有发生任何改变。因此,所制备的催化剂具有优异的可循环利用性和稳定性。将NiFe2O4运用在11种不同结构的醛与丙二腈或氰乙酸乙酯反应中,发现催化剂对反应具有良好的普适性,底物醛分子中吸电子取代基以及苯环的存在对反应效果有积极的影响。另外,活泼亚甲基的活性与其两端吸电子基团的电负性呈正相关性。
[Abstract]:Magnetic nanomaterials with special physical and chemical properties have been widely used in the fields of electronics, information, automatic control, organic synthesis, biomedicine and so on, especially in the field of catalysis. As a catalyst or catalyst carrier, magnetic nanoparticles have excellent performance, and it also has magnetic separation properties. Knoevenagel condensation reaction is one of the most important reactions to form CfC, and the condensation product is an extremely valuable synthetic intermediate. Therefore, the application of magnetic nanomaterials as green and environmentally friendly catalysts for the study of Knoevenagel condensation reaction is expanded. It is not only innovative in basic research. Magnetic nanomaterials as catalysts for Knoevenagel reaction are studied in the following two aspects. Fe3O4@SiO2 magnetic nanocrystalline catalyst was prepared by solvothermal method and Stober method. The Knoevenagel condensation of benzaldehyde and malonitrile was used as probe reaction, and the reaction conditions were optimized to realize the complete conversion of benzaldehyde under the optimum conditions. The yield of the target product was 97.8. at the same time, the experimental results of different catalysts were compared. It is inferred that the active component of Fe3O4@SiO2 catalyst is Si02 layer. The cycle experiment shows that Fe3O4@SiO2 catalyst can still maintain the conversion rate of 90.1% and 9% under the 7th cycle. 3.5% selectivity. The structure and composition of the catalyst have not changed in reuse. Therefore, the prepared catalyst has excellent reusability and stability. Fe3O4@SiO2 magnetic nanocrystalline catalyst can be separated by external magnetic field. It is easy to operate and has a good prospect of industrial application. Fe3O4@SiO2 was applied to the reaction of aldehydes with malonitrile with 11 different structures. The results showed that most of the reactions could be carried out quickly under the action of catalyst. On the other hand, a series of MFE _ 2O _ 4 / M _ 2O _ 4 and mn _ (mn) Cu _ (2 +) were prepared by one-step solvothermal method. Zn and Ni) magnetic nanoparticles were prepared by FTIR and XRDX Tem BET. Knoevenagel condensation of benzaldehyde and malonitrile was also used as model reaction to study the catalytic effect of different MFe2O4 nanoparticles on the reaction. The results showed that the catalytic activity of NiFe2O4 was the best. At the same time, it is inferred that M element is the key active component of MFe2O4. Optimizing the amount of NiFe2O4 catalyst can make the yield of target product up to 98.6. It was found that the activity of NiFe2O4 could maintain the conversion of 95.1% and the selectivity of 96.2% after the 8th cycle use. And the structure and composition of the catalyst has not changed in the reuse. The prepared catalyst has excellent reusability and stability. NiFe2O4 was used in the reaction of aldehydes with malonitrile or ethyl cyanoacetate with 11 different structures. It is found that the catalyst has a good universality for the reaction, and the presence of the electron-absorbing substituents and benzene rings in the substrate aldehydes has a positive effect on the reaction effect. The activity of active methylene is positively correlated with the electronegativity of the electron-absorbing groups at both ends.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：O643.36;TB383.1

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