Preparation And Application Of Metal Catalyst Supported By Magnetic Micro-spheres

Metal has highly efficient catalytic performance when reducing its size. If the metal has been loading on the magnetic micro-spheres, it will make the metal catalyst have a magnetic response, easy to be recycled and reused many times with highly active. In this paper, we prepared Fe3O4 micro-spheres with a polyol method, and then amino-modified its surface to get carrier Fe3O4@NH2 micro-spheres. Fe3O4@NH2-M (0) catalyst was obtained with in situ reduction method and was applied for catalytic hydrogenation of 4-NP. In this thesis, we carried out in the following aspects:(1) The water dispersed Fe3O4 particles were synthesized according to a polyol method; FeCl3·6H2O was introduced as an iron source; ethylene glycol was introduced as a solvent and reducing agent, urea was introduced as a precipitating agent; sodium citrate was introduced as stabilizer; the reaction condition was under 200℃ with 12h. There was no generation of Fe3O4 without adding urea; sodium citrate played a dominant role in controlling the size of Fe3O4 micro-spheres; the ratio of the synthesis of spherical, mono-disperse particle, diameter of about 250nm, a magnetometer 67.35 emu/g of Fe3O4 micro-spheres were the amount of 0.97 g FeCl3·6H2O,3.6g urea,0.32 g sodium citrate and 30mL ethylene glycol.(2) It directly hydrolyzed and condensed by a single silicon source 3-aminopropyl triethoxysilane (APTES) on Fe3O4 micro-spheres, introduced aminopropyl and produced carrier magnetic Fe3O4@NH2 micro-spheres, then controlled the addition of dilute concentrations precursor AuCl4-, complexed-NH2 and AuCl4- under ultrasonic vibration and mechanical agitation, added NaBH4 to reduce AuCl4-, synthesized magnetic Fe3O4@NH2-Au monodisperse microspheres, speculated preparation of the catalyst possible mechanism.(3) Selecting Fe3O4@NH2 microspheres as the carrier to individually support Au, Pt, Pd, and Cu produced supported magnetic catalyst which has been applied in catalytic hydrogenation of 4-NP. As the concentration of metal precursor was added to, the catalytic performance of the catalyst was decreased after the first increased; the best catalytic performance corresponded to the concentrations of 0.1 mg/mL HAuCl4·3.5H2O,0.3mg/mL H2PtCl6·6H2O, 0.1mg/mL PdCl2,2mg/mL CuCl2·2H2O. Amino-modified Fe3O4@NH2 had an strong force with varieties of metals, which had general applicability. Therefore, the method we used could be applied in preparation of different metal catalyst supported by magnetic microspheres, which was in wide applications.(4) Selecting carrier Fe3O4、Fe3O4@SiO2-APTES and Fe3O4@NH2 respectively supported Au, which was applied in 4-NP catalytic hydrogenation. The catalytic performance of Fe3O4@NH2-Au was the best, which proved that the preparation method was conducive to carrier Fe3O4@NH2 supporting Au, and Fe3O4@NH2 was with high amino density. In the meanwhile, it had the stronger coordination with gold ions.