Synthesis Of Supported Au And Au@Pd NPs On Magnetic Polymer Microspheres And Their Application In Catalysis

Magnetic polymer microspheres had the prominent advantages over magnetic separation and rich surface functional groups,which made it be an excellent carrier for catalysts.The surface of magnetic polymer microspheres were functionalized to change the interaction and adsorption capacity between the carriers and gold nanoparticles(Au NPs).The reduction of p-nitrophenol(4-NP)was employed to evaluate the catalytic activity of immobilized Au nanoparticles.This paper mainly focused on preparation of modified magnetic microspheres and catalytic performance of the supported Au NPs and AuPd NPs.The main contents are as follows:(1)After the micrometer-sized magnetic PMMA microspheres were prepared with microsuspension polymerization,Au NPs with uniform size were immobilized on its surface to prepare the supported Au NPs catalysts.Then,a series factors,such as the effect of adsorption,particle size of Au NPs and supporting density were studied to reveal the influence on the catalytic activity.Finally,the stability and reusability of the supported Au NPs catalysts were also studied.(2)Compared with micrometer-sized magnetic PMMA microspheres,nano-sized magnetic PS microspheres with smaller particle size,larger specific surface area and stronger ability to adsorb reactants were prepared with miniemulsion polymerization.Then the surface of these microspheres were modified with amino groups for supporting Au NPs.Then,the effects of carrier adsorption on the reactants,gold nanoparticles and supporting density on the catalytic activity were carefully investigated.The reuse performance of the supported nano-gold catalyst(Au/Fe3O4@PS)was also studied.(3)Based on Au/Fe3O4@PS,Au NPs was replaced by gold-palladium core-shell nanoparticles(AuPd NPs).The effect of palladium coverage on the catalytic activity was investigated.At the same time,the re-use performance of the supported AuPd NPs catalyst was also studied.The responding results are as follows:(1)The magnetic PMMA microspheres with average particle size of 7.8 ?m were prepared to support the Au NPs.The effects of supporting density and particle size on the catalytic behavior were studied.The supported 10 nm Au NPs catalyst called SAu-10-2(4292 ?g/g)showed the highest catalytic activity.Only depending on controlling the loading density and particle size of Au NPs,the catalytic activity of the supported Au NPs catalyst could be close to that of the quasi-homogeneous gold nanoparticles.The recycling runs of the catalyst reached 23.(2)The Au NPs was loaded on magnetic PS microspheres with an average particle size of 110 nm.The effects of supporting density and particle size on the catalytic behavior were carefully studied.Compared with the isolated Au NPs,the catalytic activity of the supported 3.8 nm Au NPs catalyst improved 6.65 times.Supporting density of Au NPs also has an important role on the catalytic activity.With the supporting density of 2211 ?g/g,SA-3.8 reached the highest catalytic activity.SA-3.8 also showed excellent substrate adaptability.The catalytic activity of SA-3.8 prepared in this chapter is also higher than that of reported supported Au NPs catalysts.This catalyst could be reused for 45 times without significant loss of catalytic activity.(3)Five kinds of AuPd NPs with different palladium coverage were prepared and the effects of Pd coverage and carriers on the catalytic activity were investigated.Compared with nano-gold and nano-palladium,the catalytic activity of AuPd NPs has been greatly improved.The k-value of AuPd NPs reached 2.39 min-1.The AuPd NPs(Au:Pd=1:1.13)was immobilized on magnetic PS microspheres prepared in the previous chapter,and the catalytic activity was nearly three times higher than that of the AuPd NPs.The TOF of this catalyst was as high as 65000 h-1.The supported AuPd NPs catalyst could be repeated for 30 times.Therefore,this paper expands the effective method of Au NPs supported on the surface of carriers.Catalytic activity of supported Au NPs catalysts were improved effectively by the synergetic effect.And this work lay the theoretical foundation for the extended use of Au NPs catalysts.