| Aromatic amines are vital raw materials and intermedi for the manufacture of diverse chemicals such as dyes, pigment, pesticides, herbicides, agrochemicals, surfactant, polymer,textile assistant and so on. They are usually synthesized from the corresponding aromatic nitro compounds by reduction. The conventional reduction approaches mainly uses metal/acid and alkali sulphide. These methods are not considered as environmentally benign process. Catalytic hydrogenation is friendly to environment, but it needs expensive equipment and the chemical selectivity is poor. Compared to the other methods,heterogeneous catalytic reduction method has the merits of low production cost, high yield,high selectivity, and less pollution to the environment. What is more, the catalyst can be recycled easily. So an increasing number of researchers have shifted their attention to catalytic reduction in recent years.Graphene exhibits a great application potential in catalysis thanks to its particular two-dimensional structure, rich stacking π-electron system, large specific surface area,remarkable electrical conductivity, high chemical and thermal stability and easy modification. Metal organic framework matarials(MOFs) with the diversity of porosity and pore shape, large specific surface area, structural diversity, the unsaturated of mental complexing, have attracted increasing attention in catalysis.In this thesis work, graphene and MOFs-supported metal or metal oxide catalysts were prepared and used as the catalysts for the selective reduction of nitroarenes.This dissertation is mainly concerned with the following aspects:1. A superparamagnetic Fe3O4-graphene nanocomposite(Fe3O4-G) was synthesized by coprecipitation method. The properties of the magnetic catalyst were characterized by scanning electron microscopy, X-ray diffraction and vibrating sample magnetometer.Fe3O4-G was used as an effective catalyst for the reduction of nitroarenes by hydrazine hydrate with the yield ranging from 75% to 92%. The catalyst can also be reused five times without an observable loss of its activity.2. A superparamagnetic copper ferrite–graphene hybrid nanocomposite(Cu Fe2O4-G)was synthesized by a solvothermal method. The properties of the magnetic catalyst were characterized by scanning electron microscopy, X-ray diffraction and Fourier transforminfrared spectroscopy. Cu Fe2O4-G was used as an effective catalyst for the reduction of nitroarenes by Na BH4 with the yield ranging from 91% to 99%. The catalyst can also be reused five times without an observable loss of its activity.3. A magnetically separable and highly active Co–Cu mixed spinel catalyst,Cu6/7Co1/7Fe2O4–graphene(Cu6/7Co1/7Fe2O4-G) was synthesized by a solvothermal method.The properties of the magnetic catalyst were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, transmission electron microscopy, fourier transform infrared spectroscopy and inductively coupled plasma atomic emission spectroscopy. Cu6/7Co1/7Fe2O4-G was used as an effective catalyst for the reduction of nitroarenes by Na BH4 with the yield ranging from 91% to 99%. The catalyst can also be reused five times without an observable loss of its activity.4. Multifunctional highly dispersed Pd nanoparticles supported on the metal-organic framework core-shell nanocomposite(Pd@ZIF-8), was prepared by a preferred strategy.The approach implies two processes: the functionalization of Pd NPs surfaces with polyvinyl pyrrolidone(PVP) and the crystallization of ZIF-8 at the surface of Pd NPs. The particles were characterized by scanning electron microscopy, high-resolution transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and inductively coupled plasma atomic emission spectroscopy. The Pd@ZIF-8 exhibits excellent catalytic activity toward the catalytic reduction of 4-nitrophenol to4-aminophenol in the presence of Na BH4 at room temperature. |
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