Preparation Of Magnetic-polymer Nanocompostie-supported Au(Ⅲ)、Au(0)Catalyst And Their Application In Catalysis

Homogeneous Au catalysts can be used in catalyzing many kinds of organic reactions under mild conditions. However, in the course of the reaction, post-processing is cumbersome and the homogeneous Au catalysts drain away easily. To overcome these shortcomings, supported Au catalysts have drawn much attention in the last dacades.Magnetic nanoparticle is widely used for supporting the homogeneous metal catalysts because it has large surface area, excellent modificability and powerful magnetic property. Large surface area makes the magnetic nanoparticles suppoted Au catalysts contact with the substrate favorably; the excellent modificability means that ligands which have good coordination with Au can be used to achieve high-load efficiency and maintain the stability of the supported Au catalyst in the process of recycling; powerful magnetic property means the supported catalysts can be quickly separated from the reaction system in an external magnetic field. Based on the above considerations, we prepare Fe3O4-polymer nanocomposite supported Au catalysts: Au/Fe3O4@SiO2-PVP、Au/Fe3O4@PMAA-DPA、nano-Au/Fe3O4@SiO2-PVP, then aromatic bromination with NBS and aerobic oxidation of benzyl alcohol are used to inspect the catalytic activity and recoverability of those suppoted Au catalyst. The main contents are as follows:1A pory(N-vinyl pyrrolidone) grafted Fe3O4magnetic nanocomposite (Fe3O4@SiO2-PVP) is prepared by radical polymerization, then loading Au (Ⅲ) to obtain catalyst Au/Fe3O4@SiO2-PVP, and characterized by using FT-IR、TEM、VSM、ICP etc.. This catalyst exhibites outstanding catalytic performance comparable to that of AuCl3for the aromatic bromination with NBS, and the catalyst could be separated from the reaction system quickly by using an external magnet. The supported Au (Ⅲ) catalyst shows high stability, and allows to be used in five runs without apparent loss of activity.2Fe3O4@PMAA-DPA nanocomposites are synthesized via2,21-dipyridyl amine (DPA) link with poly(methacrylic acid) modified magnetic nanoparticles, then Fe3O4@PMAA-DPA nanocomposites are used to load Au (Ⅲ) to obtaine Au/Fe3O4@PMAA-DPA catalysts, and characterized by using FT-IR、AAS、TEM, VSM、XRD etc. This catalyst exhibites outstanding catalytic performance comparable to that of AuCl3for the aromatic bromination with NBS, and it could be separated from the reaction system quickly by using an external magnet. The supported Au (Ⅲ) catalyst allows to be used in five runs without apparent loss of activity.3Fe3O4@SiO2-PVP nanocomposites suppoted three different size nano-Au catalysts nano-Au/Fe3O4@SiO2-PVP are prepared, and characterized by TEM, XRD and VSM. The oxidation reaction results of the benzyl alcohol for the three different nano-Au catalysts show mat the smaller the particle diameter of the gold nanoparticles are, the higher the catalytic activity is. The catalyst with the smallest size of Au is used in catalyzing the aromatic alcohol aerobic oxidation reaction in the aqueous phase. The results indicate that the catalyst has excellent catalytic activity and could be separated from the reaction system quickly by appling an external magnetic field. The supported nano-Au catalyst allows to be used in five runs without apparent loss of activity, the yield still remain87%. The reaction uses water as its medium, means that it is environmentally friendly.