Synthesis Of The Magnetic Pd Nanocatalyst And Its Application In Organic Reactions

In recent years, the interest in catalysis by metal nanoparticles is increasing dramatically because of the high surface area per volume and catalytic activity of metal nanoparticles. However, the nanoparticles are easy to reunite, difficult to separation, short life and thus limits their practical application. Therefore, developling a heterogeneous catalyst system with high dispersion and long life is becoming the research focus in the field. It is worth noting that the surface- functionalized magnetic nanoparticles for immobilizing precious metals is receiving more and more attention.This thesis is mainly divided into the following four parts:(1) Fe3O4 magnetic nanoparticles is first prepared by co-precipitation and silica coated magentic particles were prepared by a reverse microemulsion. Secondly,silica coated magnetic nanoparticles were functionalized with APTS and succinic acid chloride and palladium choloride was supported on the surface of XL-Pd(II)-Fe3O4@SiO2 and the palladium chloride reduced to palladium particles with sodium borohydride. XL-Pd(?)-Fe3O4@SiO2,XL-Pd(0)-Fe3O4@SiO2 catalysts were characterized by TEM, XRD, VSM, FT-IR and XPS. the catalyst XL-Pd(0)-Fe3O4@SiO2 was used for a variety of aromatic nitro compounds and hydrogenation of unsaturated compounds and XL-Pd(?)-Fe3O4@SiO2 was used for the Suzuki coupling reactions. The XL-Pd(0)-Fe3O4@SiO2 catalyst has high catalytic activity and in short reaction time the most of the yield of the product reached 92% on the nitro compounds of different types. In Suzuki coupling reaction XL-Pd(?)-Fe3O4@SiO2 catalyst showed very high catalytic activity even at room temperature. Two kinds of catalysts are easily separated from the reaction mixture and after 6 cycles the catalytic activity had been no obvious changed.(2) Firstly, Fe3O4 nanoparticles are attached onto carboxylic PS latex surface via electrostatic attraction under acidic solution. Then, the shell is formed by simultaneous sol-gel polymerization of tetraethoxysilane (TEOS) and n-octadecyl-trimethoxysilane (C18TMS) mixture on the heteroaggregate. the PS latex and the organic groups wereremoved by calcination so that HMMS is obtained.HMMS were prepared. Secondly,the functionalization of the silica coated HMMS with 3-(2-aminoethylamino) propyltrimethoxysilane. Thirdly, Palladium chloride was supported on the surface of HMMS, and the palladium chloride reduced to palladium particles with sodium borohydride.The catalysts were characterized by TEM, XRD,VSM, FT-IR and XPS. The catalsyt was used for the coupling reactions and the hydrogenation of unsaturated and nitro compounds. The XL-Pd(0)-Fe3O4@SiO2 catalyst has high catalytic activity and in short reaction time the most of the yield of the product reached 92% on the compounds of different types. . In addition, it was found that the catalyst also showed a high activity for Suzuki coupling reaction. (most substrates yield can reach 90% ) and the catalyst could be recycled six times without any loss in activity.(3 ) The hollow Fe3O4 nanoparticles were synthesized by a facile solvothermal sythetic strategy. Second, the fuctionalization of hollow Fe3O4 with APTS. Thirdly,palladium chloride was supported on the surface of hollow Fe3O4, and the palladium chloride reduced to palladium particles with sodium borohydride?.The catalyst afforded fast conversions for various aromatic nitro compounds under H2 atmosphere in ethanol even at room temperature. Furthermore, it was found that the catalyst showed a high activity for the suzuki reaction, affording over 80% yield in all the cases investigated. Interestingly, the catalyst could be facilely recovered from the reaction mixture and recycled fifth times without significant loss in activity.(4) Frist, the magnetite particles were prepared by a robust solvothermal reaction.Second,a thin layer of polypyrrole (PPy) was coated on the surface and interior the magnetite particles. Third, the noble metal salt (PdCl2) was used as precursor and it was first absorbed by Fe3O4/PPy in ethanol, followed by NaBH4 reduction, generating Pd (0) nanoparticles decorated Fe3O4/PPy composites. Our catalyst afforded great yields of Suzuki and Heck coupling reactions in neat water under atmospheric pressure(most substrates may be more than 75% yield ). the catalyst could be facilely recovered from the reaction mixture and recycled fifth times without significant loss in activity.