磁性纳米催化剂的制备及催化氧化合成葡醛酸的研究

发布时间：2018-01-19 20:43

本文关键词： 四氧化三铁催化剂对硝基苯酚葡甲苷　出处：《武汉工程大学》2015年硕士论文　论文类型：学位论文

【摘要】：磁性纳米催化剂由于其具有高催化活性和方便的磁性回收的特性,在光催化、有机合成催化和废水处理方面表现出了传统催化剂无法相比的优势。其中合成简单、磁性强的四氧化三铁通常被作为催化剂载体的核心,再通过表面包覆方法即可得到分散均匀、比表面积大且具有磁性的复合纳米材料,因而磁性纳米催化剂得到了广泛研究。本论文以共沉淀法合成了四氧化三铁,并通过二氧化硅包覆得到稳定、分散性好的Fe_3O_4@SiO_2载体,再通过表面修饰和接枝的方法得到磁性纳米载体,负载活性中心钯后,进一步用聚乙稀吡咯烷酮(PVP)固定活性中心经还原得到催化剂,或通过接枝后和锰离子配位得到配合物催化剂。对各步产物用红外、紫外、热重(TGA)、透射电镜(TEM)、X射线衍射(XRD)和X射线电子能谱(XPS)进行了结构表征。分别考察了钯催化剂对对硝基苯酚(4-NP)的还原性能及重复利用的使用性能,同时研究了这些催化剂对于α-D-甲基葡萄糖苷(葡甲苷)的氧化性能。主要研究工作如下:1.合成了具有核壳结构的Fe_3O_4@SiO_2及包覆介孔结构二氧化硅的Fe_3O_4@mp-SiO_2,再通过浸渍Pd(NH3)4Cl2负载活性钯,包覆PVP还原后得到催化剂Fe_3O_4@SiO_2-Pd和Fe_3O_4@mp-SiO_2-Pd。催化剂在硼氢化钠作为还原剂作用下对4-NP具有良好催化效果,两个催化剂对于4-NP的还原的速率常数分别为K1=0.641 min-1,K2=0.591 min-1,且两个催化剂重复利用5次仍具有较好的活性,转化率均高于86%。两个催化剂催化在四倍当量的双氧水及pH=7-8条件下氧化葡甲苷得到葡醛酸的收率分别为39.8%和50.2%。2.利用γ-氨丙基三甲氧基硅烷和γ-巯丙基三甲氧基硅烷对Fe_3O_4@SiO_2的表面改性,再分别以Na2[PdCl4]和PdCl2为钯源负载活性中心,包覆PVP后还原得到催化剂Fe_3O_4@SiO_2-NH_2-Pd和Fe_3O_4@SiO_2-SH-Pd。研究了他们对4-NP的催化还原性能,催化反应速率常数分别为K1=0.435 min-1,K2=0.514 min-1,且催化剂循环利用5次后催化活性无明显降低。催化剂在相同条件下对于葡醛酸的收率分别为24.1%和33.71%。3.用2,4-二羧基苯甲醛与乙二胺反应(摩尔比2:1)得到双席夫碱化合物,然后利用硼氢化钠还原得到含酚羟基及多氮的配体(L1);另外,利用γ-氯丙基三甲氧基硅烷和γ-氨丙基硅烷偶联剂修饰Fe_3O_4@SiO_2表面,再分别利用Williamson合成和酰化反应与配体L1或EDTA接枝,最后与锰配位得到催化剂Fe_3O_4@SiO_2-Cl-L1-Mn和Fe_3O_4@SiO_2-NH_2-EDTA-Mn。测试了催化剂对于葡甲苷的催化氧化性能,对应的葡醛酸的收率分别为25.2%和35.4%。
[Abstract]:Magnetic nanocatalysts have high catalytic activity and convenient magnetic recovery properties in photocatalysis. Organic synthesis catalysis and wastewater treatment show advantages that can not be compared with traditional catalysts. Iron trioxide, which is a simple and magnetic catalyst, is usually used as the core of catalyst carrier. Then the composite nanomaterials with uniform dispersion, large specific surface area and magnetic properties can be obtained by surface coating method. Therefore, magnetic nanocatalysts have been extensively studied. In this thesis, ferric oxide has been synthesized by co-precipitation method. The stable and dispersible Fe_3O_4@SiO_2 carrier was obtained by the coating of silica, and then the magnetic nano-carrier was obtained by surface modification and grafting method, and the active center palladium was loaded. The catalyst was further fixed with polyvinyl pyrrolidone (PVP) and the catalyst was obtained by reduction, or by coordination with manganese ion after grafting. The products of each step were obtained by IR and UV. TGA, TGA, TEM (TEM). The structure of p-nitrophenol 4-NPs was characterized by X-ray diffraction (XRD) and X-ray electron spectroscopy (XPS). The reduction performance and reuse performance of palladium catalyst for p-nitrophenol 4-NPs were investigated. The effects of these catalysts on 伪 -Dmethylglucoside (glucoside) were also studied. The main research work is as follows: 1. Fe_3O_4@SiO_2 with core-shell structure and Fe_3O_4@mp-SiO_2 coated with mesoporous silica have been synthesized. Then the active palladium was impregnated with Pd(NH3)4Cl2. After reduction with PVP, the catalyst Fe_3O_4@SiO_2-Pd and FeSZ _ 3O _ 4O _ 4s _ p _ p _ p _ 2-Pd _ 2-Pd were obtained. The reaction of catalyst with sodium borohydride as reducing agent for 4-N was carried out. P has good catalytic effect. The rate constants of the reduction of 4-NP on the two catalysts were 0.641 min-1 ~ (-1) min ~ (-1) K _ (2) O _ (0.591 min-1), respectively. The two catalysts still have good activity for 5 times. The yield of glucuronic acid was 39.8% and 50.2% respectively under the condition of four times equivalent hydrogen peroxide and pH=7-8. Surface modification of Fe_3O_4@SiO_2 by aminopropyl trimethoxy silane and 纬 -mercapto trimethoxy silane. And then separate the Na2. [PdCl4] and PdCl2 are palladium source loaded active centers. The catalytic reduction of 4-NP by PVP was studied. The catalytic reduction of 4-NP was carried out by using the catalyst Fe_3O_4@SiO_2-NH_2-Pd and FeSs _ 3O _ 4os _ 4O _ 2O _ 2-SH-Pd.The catalytic reduction of 4-NP was studied. Performance. The rate constants of catalytic reaction were 0.435 min-1 ~ (-1) K _ (2N) 0.514 min-1, respectively. Under the same conditions, the yields of the catalyst for glucuronic acid were 24.1% and 33.71 respectively. BIS Schiff base compounds were obtained by the reaction of 4-dicarboxybenzaldehyde with ethylenediamine (molar ratio 2: 1). In addition, 纬-chloropropyl trimethoxy silane and 纬-aminopropyl silane coupling agent were used to modify the surface of Fe_3O_4@SiO_2. The ligands L1 or EDTA were grafted by Williamson synthesis and acylation respectively. Finally, the catalyst Fe_3O_4@SiO_2-Cl-L1-Mn and Feal _ 3O _ 4O _ 4s _ s _ 2O _ 2-NH _ 2-S _ 2-EDTA-Mn. were obtained by coordination with manganese. The catalyst for Portugal was tested. Catalytic oxidation of glucoside. The yields of uronic acid were 25.2% and 35.4, respectively.
【学位授予单位】：武汉工程大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O643.36;TB383.1

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