Study On The Controlled Preparation Of Nano-Nickel And Nano-Nickel Base Material In The Rotation Packed Bed

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.