The Preparation And Performance Study Of Magnetic Core-Shell Structure Cu/Fe₃O₄@SiO₂ Catalyst

Magnetic nanocomposites have widely applied in catalysis, ferrofluid, bio-medicine, bio-separation because of their special structures and properties. Especially, the magnetic nanocomposites based on Fe3O4 nanoparticles, can be effective separation and recovery under external magnetic field due to theirs superparamagnetism, other than the conventional magnetic materials. Core-shell structure magnetic catalytic materials are regarded as one kind of very important magnetic nanocomposites, have shown great potential for liquid-phase catalysis.In this paper, Fe3O4 nanoparticles were prepared by coprecipitation and Fe3O4@SiO2 magnetic microspheres were synthesized using sol-gel method, then the Fe3O4@SiO2 magnetic microspheres used as support, obtained Cu/Fe3O4@SiO2 catalyst according to dispersing Cu nanoparticles on the surface of the microspheres. The catalyst structures were characterized by X-ray diffraction (XRD), N2-adsorption/desorption, transmission electron microscopy (TEM), and Vibrating-sample Magnetometer (VSM) techniques. Then, the formaldehyde solution was choosed as model compound to investigate the catalystic performance of Cu/Fe3O4@SiO2 catalyst.The results indicated that the Fe3O4 nanoparticles were synthesized by coprecipitation without protective gases, with diameter 20 nm and size uniformity, high purity and integrity of crystallinity. And present superparamagnetism at room temperature, the maximum saturation magnetization is 83.2 emu/g. The Fe3O4@SiO2 magnetic microspheres with diameter about 500 nm were obtained by sol-gel method through silica coating. The magnetic microsphers posses mesoporous structure and present superparamagnetism at room temperature, the maximum saturation magnetization is 24.0 emu/g. The surface area of Cu/Fe3O4@SiO2 catalyst was about 287.7m2·g-1, the Cu nano-particles with diameter approximate 10nm, and homodispersed on the surface of Fe3O4@SiO2 micropheres.By multiplely dispersion, the Cu/Fe3O4@SiO2 catalysts with different Cu content wt 5%-20% were prepared. By studying the effect of active component content, catalyst dosage, NaOH concentration and reuse time of catalyst on the hydrogen production we found that when the Cu content was wt 15%, catalyst dosage was 0,10 g, NaOH concentration was 1.0 mol/L, the maximum volume of hydrogen generation reached 42.0 mL when the reaction performed for 40 min. The catalyst was recycled by a magnet, when the catalyst reused for 8 times, the recovery rate of catalyst was about 98%, and the maximum volume of hydrogen generation still maintained at 34 mL after 40 min.