负载型Pt基纳米复合催化剂的制备及其对4-硝基苯酚加氢的研究

发布时间：2018-09-09 08:13

【摘要】：芳胺类物质广泛应用于精细化工、燃料、医药等很多领域。通过硝芳基化合物催化加氢还原制备芳胺类物质的过程,由于具有环境友好、易操作等优点,已经成为目前生产芳胺类物质最常用的方法。而在催化加氢过程中,高效的催化剂对于生产芳胺类化合物的生产成本和产品质量具有重要影响。在本文中,主要制备了两种负载型Pt基纳米催化剂,用于4-硝基苯酚(4-NP)催化还原制备4-氨基苯酚(4-AP)的过程,研究纳米催化剂在加氢反应中的催化性能。主要包括:1、铂修饰负载型镍(NiPt)纳米催化剂的制备首先,以葡萄糖碳化后的产物为还原剂,水滑石为载体制备得到了负载型铂纳米催化剂。其次再高温煅烧得到铂修饰负载型镍纳米催化剂。具体内容为:采用类似成核/晶化隔离法制备得到镍铝水滑石(NiAl-LDH)前躯体,将NiAl-LDH前躯体与葡萄糖溶液混合,在晶化过程中,加入氯铂酸,使晶化过程与还原过程同时进行,从而制得高度分散的负载型铂纳米催化剂(Pt@LDH/C)。将Pt@LDH/C高温煅烧得到铂修饰负载型镍纳米催化剂(NiPt)。通过调变焙烧温度考察了制备条件对纳米催化剂形貌结构的影响,最终确定出最优的制备条件。2、纳米催化剂的形貌和Pt的负载量对催化性能的影响在最佳的制备条件下,改变铂的负载量,制备出一系列铂负载量不同的NiPt纳米催化剂,并对纳米催化剂的结构形貌等进行了一系列的表征,考察了纳米催化剂的催化性能。结果表明:当铂的理论负载量为0.6%时,纳米催化剂的活性最高。3、以生物质为原料熔盐法制备生物多孔炭(PC)催化剂载体在本研究中,生物质通过一个简单的熔盐合成过程转化为多孔炭。通过这种方法碳化和活化过程能够一步完成,并且由于熔盐氯化锌提供了一个较好的熔融环境,所以,碳化时间和温度显著的降低了。多孔炭的性质通过XRD、TG-DSC、SEM、TEM、FT-IR和BET吸脱附等温线表征。结果表明制备的多孔炭是无定形的,具有分级孔结构并且比表面积高达1642 m2g-1,表面富含多种官能团。这些官能团能够提供较多的吸附位点。4、二氧化锡与多孔炭复合物的制备及其对Pt纳米催化剂的负载与催化性能研究首先,用溶剂热法制备二氧化锡-多孔炭(SnO_2-PC)复合物。然后,再以乙二醇(EG)为还原剂,SnO_2-PC复合物为载体,制备得到了负载型铂纳米催化剂(Pt@SnO_2-PC)。具体内容为:以氯化亚锡为锡源,碱性乙醇为还原剂和溶剂,在溶剂热的条件下与多孔炭混合,制备出SnO_2-PC复合物。然后,再以此复合物为载体,以EG为还原剂,在乙二醇/水体系中,通过溶剂热法制备Pt@SnO_2-PC。并对纳米催化剂的结构形貌等进行了一系列的表征,考察了纳米催化剂的催化性能。确定出氧化物对纳米催化剂活性的影响。结果表明:SnO_2-PC对实验无催化作用;在相同Pt负载量的情况下,与Pt@PC相比,Pt@SnO_2-PC具有较高的活性。说明SnO_2对催化具有促进作用。
[Abstract]:Aromatic amines are widely used in many fields, such as fine chemical industry, fuel, medicine and so on. The process of preparing aromatic amines by catalytic hydrogenation reduction of nitroaryl compounds has become the most commonly used method for the production of aromatic amines because of its environmental friendliness and ease of operation. In the process of catalytic hydrogenation, the efficient catalyst has an important effect on the production cost and product quality of aromatic amines. In this paper, two kinds of supported Pt based nanocatalysts were prepared for the catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). The main results are as follows: (1) Platinum modified supported nickel (NiPt) nanocatalysts were prepared. Firstly, supported platinum nanocatalysts were prepared by using glucose carbonized products as reducing agent and hydrotalcite as support. Secondly, platinum modified supported nickel nanocatalysts were obtained by calcining at high temperature. The main contents are as follows: the nickel aluminum hydrotalcite (NiAl-LDH) precursor was prepared by similar nucleation / crystallization isolation method. The NiAl-LDH precursor was mixed with glucose solution. In the process of crystallization, chloroplatinic acid was added, so that the crystallization process and the reduction process were carried out simultaneously. A highly dispersed supported platinum nanocatalyst (Pt@LDH/C) was prepared. Preparation of Platinum modified Nickel Nano-catalyst (NiPt). By calcining Pt@LDH/C at High temperature The effects of preparation conditions on the morphology and structure of nano-catalysts were investigated by changing the calcination temperature, and the optimum preparation conditions were determined. The effects of the morphology of nano-catalysts and the amount of Pt loading on the catalytic performance were obtained under the optimum preparation conditions. A series of NiPt nanocatalysts with different platinum loading were prepared by changing the loading amount of platinum. The structure and morphology of the nanocrystalline catalysts were characterized and the catalytic properties of the nanocrystalline catalysts were investigated. The results showed that when the theoretical loading amount of platinum was 0.6, the activity of nanometer catalyst was the highest. The bioporous carbon (PC) catalyst carrier was prepared by using biomass as raw material and molten salt as raw material in this study. Biomass is converted into porous carbon through a simple molten salt synthesis process. The carbonation and activation process can be completed in one step by this method, and the carbonation time and temperature are significantly reduced because the molten salt zinc chloride provides a better melting environment. The properties of porous carbon were characterized by XRD,TG-DSC,SEM,TEM,FT-IR and BET adsorption isotherms. The results show that the prepared porous carbon is amorphous, with a graded pore structure and a specific surface area of 1642 m2g-1.The surface is rich in various functional groups. These functional groups can provide more adsorption sites. 4. Preparation of Sno _ 2 / porous carbon complexes and their support and catalytic performance on Pt nanocatalysts. Firstly, solvothermal synthesis of tin dioxide / porous carbon (SnO_2-PC) complexes is studied. Then the supported platinum nanocatalyst (Pt@SnO_2-PC) was prepared by using ethylene glycol (EG) as the reductant Sno _ 2-PC complex as the carrier. The main contents are as follows: using stannous chloride as tin source, alkaline ethanol as reducing agent and solvent, the SnO_2-PC complex was prepared by mixing with porous carbon under solvothermal conditions. Then, using this complex as carrier and EG as reducing agent, Pt@SnO_2-PC. was prepared by solvothermal method in ethylene glycol / water system. The structure and morphology of the nanocatalysts were characterized and the catalytic properties of the nanocrystalline catalysts were investigated. The effect of oxide on the activity of nanometer catalyst was determined. The results show that: SnO2-PC has no catalytic effect on the experiment, and PtSn-SnO2-PC has higher activity than Pt@PC under the same Pt loading. The results show that SnO_2 can promote the catalysis.
【学位授予单位】：郑州大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：O643.36;TQ243.1

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