Environmental Friendly Preparation And Application Of Green And Efficient Recycling Catalyst

Transition metal nano-catalysts and organometallic catalysts have become a focus currently in the field of catalysis. Platinum based nano-catalysts, characterized by good stability and high catalytic activity, have been applied in a number of organic synthetic systems. Meanwhile, owing to the properties of super-paramagnetism, multiple crystal defect sites, easy-to-magnetic recycling, multi-active co-catalytic performance and so on, the iron based magnetic nanocomposite particles have been widely utilized in the field of catalysis, bio-medicine and environmental protection. However, as to platinum based nano-catalysts、iron based magnetic nanocomposite catalysts and organometallic catalysts, there are still several defects in practical application such as high-cost, low stabilization and hardest-to-recycle. To solve the aforementioned problems and endow platinum based particles with more other function, this dissertation focuses on the preparation and application of Pt/CF nano-catalysts in the hydrogenation reduction of para-chloronitrobenzene, the development and application of low-cost metal nanocomposite catalysts in the hydrogenation reduction of chloronitrobenzene, as well as the synthesis of magnetic-recyclable Cu-containing composite catalysts and their application in the Henry reaction. The detailed contents in this work can be summarized as the following four aspects.（1） Chapter I introduced the status of research and application about transition metal nano-catalysts and organometallic catalysts, focusing on catalysts studied in this work, including the synthesis, characterization and catalytic application of platinum based, magnetic nanocomposite and magnetic-recyclable catalysts containing copper complex.（2） Chapter II summarized and contrasted the deficiencies of the application of Pt/C catalyst in the process of hydrogenation reduction of chloronitrobenzen according to the reported literature. Carbon fibers（CF） with higher surface area was selected as supports to prepare green catalysts characterized by larger surface area and higher activity. Firstly, the carrier was activated by 10 mol/L KOH solution, washed and dried before undergoing temperature programming to 850°C under N₂ atmosphere in high-temperature carbonizing stove. Then, Pt nanoparticles were immobilized on the surface of CF by ultrasonic reduction. Pt/CF catalysts with Pt nanoparticles in diameter of 4.6nm were finally obtained in this work, which demonstrated super adsorption because of their larger surface area. Besides, much more powerful active sites were introduced by functionalizing-COH and-COOH to cooperate with Pt nanoparticles on the surface of Pt/CF catalysts, which showed faster electronic delivery and better ion-exchange capacity. Owing to the unique electrochemical capability of Pt/CF catalysts mentioned above, parachloroaniline was successfully solvent-free synthesized by catalyzed hydrogeneration reduction of parachloronitrobenzene.（3） Nano CoxFe_3-xO₄ composite catalysts were designed and prepared in Chapter III, based on the features that defects of crystal structure were introduced during the composition of magnetic Fe and Co as a result of changing crystalline form caused by changing molar ratio of the two elements. And the experimental results showed that Co_0.2Fe_2.8O₄ demonstrated super catalytic activity in the hydrogeneration reduction of parachloronitrobenzene to prepare parachloroaniline. Compared to already reported catalysts such as Fe₃O₄ and Co, Co_0.2Fe_2.8O₄ presented so higher performance that the yield and selectivity of parachloroaniline were nearly up to 100% at 80°C and ambient pressure with pure water as reaction media. Moreover, the catalysts could be recycled by the external magnetic field. Accordingly, a green, clean and energy efficient synthesis rout was developed in this work, avoiding the environmental pollution caused by organic solvents as well as high cost with the introduction of inert gases.（4）Chapter IV developed a novel highly-efficient magnetic-recyclable Cu-containing composite catalysts, with surface-functionalized magnetic Fe₃O₄ as supports to combine with copper and organic ligands. The new catalysts exhibited an excellent catalytic activity and reutilization in Henry reaction. Reaction yield was as high as 97% under the ambient temperature and pressure, moreover, the yield of the product could reach 89% with catalysts reused for 10 times. Notably, the synthesis rout was proved to be environmentally-friendly, because defects of currently used homogeneous catalyst in Henry reaction including complex subsequent processing, difficult reclaim, environmental pollution and high cost of production, were mostly avoided in this work.