Preparation Of Highly Dispersed Nanometal Catalysts And Their Applications In The Catalytic Transfer Hydrogenation Of Nitro Compounds

Aromatic amines are important intermediates for the synthesis of a variety of nitrogen-containing bioactive compounds,agrochemicals,dyes,polymers and so on.They are also precursors of amide,imine,azo compounds,isocyanates and diazo salts.In the traditional industry,a large number of wastewater and waste residue have been produced in the reduction of nitro compounds by iron powder,which has caused certain harm to the environment.The catalytic transfer hydrogenation reaction has the advantages of mild reaction conditions,safety,low pollution and easy operation.Heterogeneous catalysts not only overcome the shortcomings of homogeneous catalysts such as difficult to recycle,but also solve the problems of precious metal loss,heavy metal pollution and so on.Heterogeneous catalysts not only overcome the shortcomings of heterogeneous catalysts which are difficult to be recycled,but also solve the problems such as the loss of precious metals,heavy metal pollution and so on.Graphene oxide has large specific surface,good stability,high dispersibility in water and organic solvents and rich oxygen-containing functional groups on its surface,which makes graphene oxide-based materials widely used in the field of catalysis.Due to the existence of nitrogen-containing groups,nitrogen-doped carbon materials can improve the dispersion of metal nanoparticles and change the electronic structure of carbon materials at N-doping position,resulting in local charge accumulation,which shows superior catalytic performance compared with simple carbon carrier.In this paper,a series of catalysts were prepared by using graphene oxide and nitrogen-doped carbon materials as supports,and the transfer hydrogenation of nitro compounds was used as a model reaction to study the activity of the catalysts.1.Firstly,Co₃（BO₃）₂ and AgPd nanoparticles were co-deposited on the surface of graphene oxide,and then Co₃（BO₃）₂ was removed by acid corrosion.Highly dispersed AgPd nanoparticles were prepared by using cobalt as sacrificial agent to prevent the agglomeration of AgPd nanoparticles.The catalyst has good catalytic activity and chemical selectivity for the transfer hydrogenation of nitroaromatics with formic acid and ammonium formate as hydrogen sources at room temperature.The corresponding aniline derivatives were obtained in high yield.This method provides a good idea for the preparation of highly dispersed metal nanoparticles.2.We annealed VulcanXC-72R carbon and urea at 300℃to prepare N-XC72R.Nitrogen doping on the surface of carbon support can significantly enhance the affinity of metal nanoparticles to the support.Compared with VulcanXC-72R supported Pd catalyst,the nitrogen doping on the surface of carbon carrier can significantly enhance the affinity of metal nanoparticles to the support.The prepared Pd/N-XC72R catalyst has higher catalytic activity for the transfer hydrogenation of nitroaromatics with formic acid as hydrogen source at room temperature.This method provides an effective and feasible way for the preparation of N-functionalized carbon materials and the preparation of high performance ultrafine metal nanoparticles heterogeneous catalysts.3.The complexes of Co（NO₃）₂·6H₂O and Cu（NO₃）₂·3H₂O with 2,2’-dipyridyl were prepared by one-step pyrolysis with VulcanXC-72R carbon as carrier.The catalyst has a unique structure,and the metal particles are wrapped in the carbon shell,which improves the stability and dispersion of the catalyst.Under mild conditions,the catalyst showed good catalytic activity and stability for the catalytic transfer hydrogenation（CTH）of nitro compounds with aminoborane（AB）as hydrogen donor.In addition,the（DFT）calculation of density functional theory shows the electronic and adsorption properties of Cu and Co nanoparticles,which further confirms the effectiveness of the catalyst.