LDHs负载Pd催化剂的制备、表征及催化性能研究

发布时间：2018-04-21 15:20

本文选题：LDHs + 剥层　；参考：《太原理工大学》2017年硕士论文

【摘要】：Layered Double Hydroxides(LDHs)是由带正电荷的二维层板与层间平衡电荷阴离子及水分子组成的一类层状无机材料。层板表面可调的酸碱度,层板阳离子和层间阴离子化学组成可调控等特性使LDHs作为载体在制备负载型催化剂用于多相催化方面有广阔的应用前景。但是由于LDHs层板堆积严重,层间距小,比表面利用率低,制约了活性组分在其上的分散度。因此,为了解决上述问题,本文选择Pd为活性组分,拟主要从LDHs载体的改性及Pd的负载方式这两个方面进行研究,制备出高分散度的LDHs负载Pd催化剂。主要研究内容包括:一是通过剥层和嫁接APTS改善LDHs的结构,制备出高度分散,大比表面的纳米层片,将其作为载体以提高Pd的分散度;二是改变负载Pd所采用的溶剂,在乙醇中制备出小粒径,高分散的负载Pd催化剂。具体研究结果如下:1)APTS改性LDH纳米层片负载Pd催化剂的制备表征及催化性能研究采用AMOST法制备了疏松多孔的LDH纳米层片并以有机硅烷APTS对其表面改性制得一种新的载体,再负载贵金属Pd制备出催化剂。通过XRD、FT-IR、N2吸附-脱附、TEM、EDS等表征手段对所得样品进行了详细的表征。结果表明,APTS嫁接到LDH纳米层片上,使负载的Pd纳米粒子的粒径减小,分散度提高,分布范围变窄。在苯甲醇的无溶剂氧化反应中,APTS改性的催化剂表现出更高的催化活性与选择性,重复使用性和稳定性良好。本研究表明APTS改性是一种有效增强表面碱性,改善LDH纳米层片上Pd纳米粒子的分布,减小粒径尺寸,增强金属-载体间相互作用的良好途径。2)乙醇溶液制备高分散度的LDHs负载Pd催化剂分别以水和乙醇为溶剂,以传统共沉淀法方法合成的LDHs(LDH-co)为载体,采用Sol-immobilization法和浸渍法制备了负载Pd催化剂。通过TEM表征发现,无论采用何种方法,乙醇溶液中所得样品,Pd纳米粒子都具有分散度高,平均粒径小,分布范围窄等特点;而在水溶液中制备的催化剂,Pd粒子的团聚现象严重,分散度差、粒径较大。3)选择乙醇为溶剂,分别以传统方法合成的LDHs,LDH纳米层片及APTS改性的LDH纳米层片为载体,采用Sol-immobilization法制备了负载Pd催化剂,通过苯甲醇氧化反应测试发现,以传统方法合成的LDHs为载体的催化剂(Sol-Pd/LDH-co)可以达到剥层改性处理的催化效果。本研究极大地简化了催化剂的合成步骤,减少了有机溶剂的使用,提高了制备效率,符合绿色化学和可持续发展的理念。
[Abstract]:Layered Double Hydroxidesus (LDHs) is a kind of layered inorganic material composed of positively charged two-dimensional laminates and interlaminar equilibrium charge anions and water molecules. The adjustable acidity on the surface of the laminates, the controllable chemical composition of the cation and the interlayer anions on the laminates make LDHs as the carrier for the preparation of supported catalysts for heterogeneous catalysis. However, the dispersion of active components on LDHs laminates is restricted because of their serious stacking, small interlayer spacing and low specific surface utilization. Therefore, in order to solve the above problems, PD was chosen as the active component in this paper, and the modification of LDHs support and the loading mode of PD were studied to prepare the PD catalyst with high dispersion degree of LDHs. The main research contents are as follows: firstly, the structure of LDHs is improved by stripping and grafting APTS, and the highly dispersed and large surface nano-layer is prepared, which is used as the carrier to improve the dispersion of PD; the other is to change the solvent used in the loading of PD. The supported PD catalyst with small particle size and high dispersion was prepared in ethanol. The results are as follows: (1) the preparation of LDH nano-layer supported PD catalyst? Characterization and Catalytic Properties of porous LDH Nanolayers prepared by AMOST method a novel support was prepared by surface modification of organosilane APTS and a catalyst was prepared by loading noble metal PD. The samples were characterized in detail by means of XRD- FT-IRN _ 2 adsorption-desorption EDS and so on. The results show that the grafted LDH nanoparticles can reduce the particle size, increase the dispersion and narrow the distribution range. In the solvent-free oxidation of benzyl alcohol, the catalyst modified by APTS showed higher catalytic activity and selectivity, good reusability and stability. The results show that the modification of APTS is an effective way to enhance the surface alkalinity, improve the distribution of PD nanoparticles and reduce the particle size of LDH nanolayers. A good way to enhance metal-carrier interaction. 2) ethanol solution was used to prepare LDHs supported PD catalyst with high dispersion. LDH-cocatalyst was synthesized by traditional coprecipitation method using water and ethanol as solvent, respectively. Supported PD catalyst was prepared by Sol-immobilization method and impregnation method. By TEM characterization, it was found that, no matter what method was used, the Pd nanoparticles obtained in ethanol solution had the characteristics of high dispersion, small average particle size and narrow distribution range, while the aggregation of Pd nanoparticles prepared in aqueous solution was serious. The supported PD catalyst was prepared by Sol-immobilization method, which was prepared by Sol-immobilization method. The results showed that the supported PD catalyst was obtained by the oxidation reaction of benzyl alcohol, and the supported PD catalyst was prepared by using the traditional method and the APTS modified LDH nano-layer as the support, respectively, using ethanol as the solvent, the particle size of which was larger than .3. the results showed that the supported PD catalyst was prepared by the method of Sol-immobilization. Sol-PD / LDH-coo catalyst supported on LDHs synthesized by traditional method can achieve the catalytic effect of delamination modification. This study greatly simplifies the synthesis steps of the catalyst, reduces the use of organic solvents, improves the preparation efficiency and conforms to the concept of green chemistry and sustainable development.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36

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