【作者】 杨勇；

【导师】 孙宝昌； 高立东；

【作者基本信息】 北京化工大学 ， 化学工程（专业学位）， 2017， 硕士

【摘要】 纳米镍及镍基颗粒具有优异的磁学特性、光学特性、电学特性,已广泛应用于生产过程。由于液相还原法具有工艺简单、设备要求低、制备形貌粒径可控、功耗低、产量高、环保等优点,而被广泛应用。但由于传统反应器内混合的限制,产品团聚严重,粒径分布大,因此液相还原法制备纳米镍时对反应过程的混合效果提出了较高要求。超重力旋转填充床(RPB)具有强化混合和传质的作用,能够实现反应沉淀制备纳米颗粒过程粒径和粒径分布的可控。北京化工大学超重力技术中心已经成功制备出纳米CaC03、A1203、ZnO、Si02等多种纳米颗粒。本文提出了在RPB内采用液相还原法制备纳米镍粉,开展了 RPB和搅拌反应釜(STR)内纳米镍粉的制备研究,分别考察了在RPB和STR内的不同因素对纳米镍粉平均粒径的影响,并初步制备出以107 nm和42 nm纳米Ni为载体的Pt/Ni和Pd/Ni颗粒。主要内容如下:1.STR内纳米镍粉的制备研究。实验结果为:纳米镍粉的平均粒径随着NiSO4浓度、反应物配比、NaOH浓度、反应温度、NaBH4浓度的增加,呈现先减小后增大的趋势,且随着搅拌速度的提高而不断降低并趋于稳定,获得了较优操作条件:NiS04浓度为0.8mol/L、进料速度为2ml/s、反应物摩尔配比为6:1、NaOH浓度为1mol/L、NaBH4浓度为0.01mol/L、搅拌速度为2400 rpm、反应温度为80 ℃C,并在较优条件下制备出常温下稳定性良好、平均粒径107 nm的面心立方结构(FCC)的纳米镍粉。2.RPB内纳米镍粉的制备研究。实验结果为:纳米镍粉的平均粒径随着NaBH4浓度、RPB转速和RPB循环时间的提高呈现出先减小后增大的趋势,随着循环液进料速度的提高不断减小并趋于稳定,并获得了较优操作条件:RPB转速为2000 rpm、RPB环境下NaBH4浓度为0.06 mol/L、RPB循环时间为2 min、循环液进料速度为8 ml/s。在较优条件下能够制备出平均粒径42 nm的面心立方结构的纳米镍。3.纳米镍基颗粒Pt/Ni、Pd/Ni的制备研究。采用还原法将Pt、Pd负载到纳米镍粉表面,制备出双金属镍基颗粒Pt/Ni、Pd/Ni。实验比较了相同条件下107 nm和42 nm镍粉对该双金属的物化性能的影响,XRD和TEM显示产品为Ni表面负载Pt、Pd的双金属,Pt、Pd粒径大小均在5 nm以内;比表面积显示42 nm纳米镍Pt/Ni和Pd/Ni的比表面积比107 nm大。循环稳定性实验表明随着时间的增加,纳米镍负载的Pd、Pt负载率呈现出不断降低并趋于稳定的趋势,在0-8 h内表现较稳定。42 nm纳米镍负载的贵金属负载率较107 nm纳米镍高。更多还原

【Abstract】 Nano-nickel and nano-nickel based materials have advantages of magnetic,optical,electrical and catalytic properties,this have been widely applied in the industrial production.Liquid phase reduction method possesses many advantages of environmental protection,low equipment requirements and low power consumption,etc.Howere,it usually carried out in the STR,which exhibits severe agglomerate and wide particle size distribution Due to the restricton of mixing in traditional stirred tank reactor.Therefore,it should meet the requirement of mixing efficiency when liquid phase reduction method is used.High-gravity rotating packed bed(RPB)can enhance the mixing and mass transfer process,thereby realizing the control of particle size distribution with reaction precipitation methond.Beijing University of chemical technology of Higee Technology Center has successfully prepared the nano-CaCO3,Al2O3,ZnO,etc.This paper adopted RPB and STR as reactors for the synthesis of nano-nickel,and the effects of various operating conditions on the characteristic of nano-nickel were studied.The follows are the main conclusions are as follows:1.Results in the STR:the average particle diameter of nano-nickel frist decreased and then increased with the increase in reactant concentration,reactant ratio,initiator concentration,sodium hydroxide concentration and reaction temperature,and it first decreased and then kept constant with the increase in stirred speed.The optimal operating conditions were:a NiSO4 concentration of 0.8 mol/L,a reactant ratio(N2H4:NiSO4)of 6:1,a initiator concentration of 0.01 mol/L,sodium hydroxide concentration of 1 mol/L,a reaction temperature of 80 ℃ and a stirring speed of 2400 rpm,and the obtained nano nickel powder was a face centered cubic(FCC)structure with an average particle size of 107 nm.2.Results in the RPB:the average diameter of nano-nickel has a tendency of decreasing firstly and then increasing with operating conditions of NaBH4 concentration and liquid circulation time,and decreasing first and then stabilizing in liquid volumetric flow,rotation speed.Nano-Ni with a face centered cubic structure,an average particle size of 42 nm and a particle size distribution of 30-60 nm was obtained under the optimal operating conditions of NaBH4 concentration of 0.06 mol/L,rotation speed of 2000 rpm,liquid volumetric flow rate of 6 ml/s and liquid circulation time of 2 min.This research provides a novel pathway and theoretical basis for large-scale production of high quality nano-Ni.3.Preparation of Pt/Ni and Pd/Ni:XRD and TEM results displayed that the products are Pt/Ni and Pd/Ni,and the average particle sizes of Pt and Pd are both less than 5 nm.In comparison with STR,the products prepared in the RPB contain more Pd and Pt,and exhibited larger surface area.The cycle stability experiments showed that,the nano-nickel prepared in the RPB have a more load rate of Pt or Pd,and the precious metals rate shows a downward trend over 0-2 h under the same conditions.更多还原