RESUMO
A novel core-shell structured nanocatalyst (Fe3 O4 @SiO2 -NH2 -FeCu nanoparticles) with ultrafine FeCu alloy NPs magnetically immobilized in porous silica has been fabricated. The obtained catalyst revealed excellent activity and chemoselectivity for catalyzing the hydrogenation of nitroarenes to corresponding anilines using hydrazine hydrate as the hydrogen source, and the reaction could be carried out smoothly in water, which is an environmentally friendly solvent. The FeCu alloy effectively prevented the dehalogenation of halonitroarenes, and X-ray photoelectron spectroscopy (XPS) study showed that it resulted from the electron-enrichment of Fe from Cu. A kinetics study indicated that the reaction order was about 1.5 towards 4-CNB and the apparent active energy (Ea ) was 48.1â kJ mol-1 , which is a relatively low value. Furthermore, the FeCu NPs are magnetically immobilized in the silica spheres (Fe3 O4 @SiO2 ), therefore the catalyst can be easily recovered by use of an external magnet and also possesses a long life time.
RESUMO
A multicomponent nanocatalyst system was fabricated for the transfer hydrogenation of nitrile compounds. This catalyst system contains palladium, copper, and iron, which are supported on the magnetite nanospheres, and the loading of palladium could be at the parts per million level. Palladium and copper contribute to the transformation of nitrile, and the product distribution highly depends on the alloying of Fe to Cu. The nitriles could be converted to primary amine by the Pd-Cu catalyst in the absence of Fe, whereas in the presence of Fe the products are secondary amines with high selectivity. This could be attributed to the electronic modulation of iron to copper. A variety of nitriles have been transformed to the corresponding primary or secondary amines with high selectivity, and the TOF reaches 2,929 hr-1 for Pd. Furthermore, the catalyst could be recycled by an external magnetic field and reused five times without severe activity loss.