Study On The Catalytic System Of Palladium Prepared From Microemulsions And Its Catalytic Behaviors

In this paper,based on the relationship between surfactants and the stability of microemulsion,three surfactants(cetyltrimethylammonium bromide(CTAB), Cetylsulfonylacetic acid and octadecyl amine polyoxyethylene ether(5)(OAPE-5))and CTAB mixed with Span 80,OAPE-5 were studied to prepare palladium microemulsion.The feasibility of preparing palladium nanoparticles and hydrogenation in those microemulsions were investigated.We found the stable microemulsion OAPE-5/HTA system,and the factors that influenced the stablility of microemulsion and the catalytic performance of palladium nanoparticles made in microemulsion were studied.The state of palladium before and after hydrogenation was investigated by UV-Vis spectra.And the performance of hydrogenation of o-chloronitrobenzene catalyzed by palladium nanoparticles in microemulsion was analysed by HPLC.In the stable microemulsion OAPE-5 system,the relationship between palladium and stabilizer were investigated by the changes of UV-Vis spectra.Different nanoparticles stabilizers were corresponding to different UV-Vis spectra absorption peaks.The results showed that HTA as palladium nanoparticles' stabilizer could prevent nanoparticles from aggregating effectively, and hydrogenation in microemulsion was easily carried out.We drew the Phase Diagrams of OAPE-5 microemulsion,and the factors that influenced the stablility of microemulsion were studied by fish-like diagrams.The hydrogenation of o-chloronitrobenzene was carried out by palladium nanoparticles in OAPE-5/HTA microemulsion.The size and structure of the nanoparticles have been characterized by TEM and XRD.The effects of microemulsion composition on particles have been investigated by FTIR.The factors that influenced the sability of the system such as alkaline agent,anount of HTA,W value,temperature and pressure were studied.We simply analysed the mechanism of hydrogenation of o-chloronitrobenzene in this paper.And by using the special properties of cetylsulfonylacetic acid which could decarboxylate at lower temperature,Pd/C catalysts modified by metal oxides nanoparticles uncoated organic substance were obtained.The stability and selectivity of modified Pd/C catalysts were investigated on hydrogenation of o-chloronitrobenzene.The characteristic of Pd/C catalysts modified by metal oxides(iron oxide and cerium oxide) before and after hydrogenation were studied by TEM and XRD.Study on the synthesis of 2,2'-dichlorohydrazobenzene by selective catalytic hydrogenation of o-chloronitrobenzene with modified Pd/C catalysts show that the introduction of oxides nanoparticles could enhance the activity and stability of Pd/C catalysts,and effective of Pd/C modified iron oxide was better.