Preparation Of Magnetic Nano Pd Catalyst And Its Application In Organic Reactions

Noble metal is a good catalyst for organic reactions of all types,When using the presence of homogeneous,it is difficult to separate.When it is used as a heterogeneous catalyst,the problem is poor dispersion?loss of the active ingredient easily and difficult to separate from the reaction system?This paper is focus on noble metal palladium catalyst system,On the basis of previous work,for improving the binding force between the active ingredient with the carrier to reduce the loss of active ingredient by studying the method of loading active ingredient,and through modifying the surface of the carrier to enhance the dispersibility of the catalyst and introducing the magnetic substance to the carrier,we can easily separate the catalyst from the reaction system by means of the Magnetic.Therefore,on the basis of previous literature we use different modification methods to develop the following four magnetic nanoparticles heterogeneous palladium catalyst,and conduct in-depth study of its catalytic activity and chemical stability.By co-precipitation method and sol-gel,we prepared Fe3O4 particles with silica wrapping,then modifying with 3-mercaptopropyl trimethoxysilane.The last,under the action of coordination and in-situ reduction of PdCl2,we prepared two kinds of catalyst.The catalysts were characterized by TEM,XRD,XPS,FT-IR and VSM.The catalysts were found to be active in both forms,Pd(II)and Pd(0),for carbonylative cross-coupling reaction of aryl iodides with arylboronic acids and hydrogenation of aromatic nitro and unsaturated compounds.In contrast to most supported catalysts,the new developed catalysts were prepared using nearly the same synthetic strategy,and are easily recovered and recycled by magnetic separation from liquid phase reactions and used for at least 5 consecutive trials without any decrease in activity.With the participation of L-dopa and FeCl3 as an iron source,we triumphantly prepared a magnetic nanocarrier end-functionalized with amino and carboxyl groups,which is good water-dispersible,by a facile one-pot solvothermal method.Under the action of coordination and in-situ reduction of PdCl2,we prepared the magnetic nano-palladium catalyst.It was characterized by TEM,XRD,XPS,FT-IR and VSM.This catalyst exhibits excellent catalytic activity for Suzuki and Heck reactions in water.Furthermore,the newly developed catalyst is easy to be recovered by magnetic separation from aqueous phase reactions.More importantly,the catalyst revealed high efficiency and high stability under the reaction conditions and during recycling stages.This catalyst can be used consecutively six times without significant loss in catalytic activity.Using the copolymers of acrylic acid and styrene(polystyrene spheres having abundant carboxyl group)as the template,in an aqueous solution,we immobilized Fe3O4 on the template with the electrostatic adsorption.The surface was coated with SiO2 and the template was burned off And then modifying the surface with 3-mercaptopropyl trimethoxysilane.The last,under the action of coordination and in-situ reduction of PdCl2,the hollow magnetic mesoporous spheres(HMMS)catalyst was synthesized.The catalyst characterized by TEM,XRD,XPS and vibrating sample magnetometry(VSM).The catalyst shows high activity for the carbonylative cross-coupling reaction of aryl iodides with arylboronic acids and Suzuki coupling reaction.The newly developed catalyst is easy to be recovered and recycled by magnetic separation from liquid phase reactions.More importantly,the catalyst revealed high efficiency and high stability under the reaction conditions and during recycling stages.In the presence of HCl solution and pyrrole monomer,the hierarchical porous Fe3O4/PPy-Pdn catalyst has been synthesized using Fe3O4 microspheres both as chemical template and oxidant source under sonication.The catalyst characterized by TEM,XRD,FT-IR,XPS and vibrating sample magnetometry(VSM).The catalyst showed high reactivity for the carbonylative cross-coupling reaction of aryl iodides with arylboronic acids.More importantly,due to the modifying of polymer,the surface of the carrier increased a number of active sites,making the chelating ability more stronger and reducing the leaching of Pd.This newly developed catalyst could be easily recovered and revealed high efficiency and high stability under the reaction conditions and during recycling stages.