Construction Of Nitrogen-doped Supported Cobalt Catalysts And Its Catalytic Performance For Reductive Amination

Amine compounds are a class of important fine chemicals,which have a very wide range of applications in the pharmaceutical,agricultural chemical and functional materials fields.Amines are mainly synthesized by alkylation of amines,Gabriel synthesis,reduction of nitriles,amides and oximes,and reductive amination.Among the above methods,reductive amination has attracted the attention of researchers because of its high efficiency and high selectivity.The synthesis of amines by reductive amination is focused on the construction of catalysts.Although heterogeneous or homogeneous catalysts based on noble metals such as Pd,Pt and Ru show good catalytic activity for the conversion process,the application of these catalysts in the industrial field is limited due to their high cost.The high abundance of non-noble metals makes them more suitable for the construction of industrial catalysts than noble metals,but most of the catalysts reported so far have low activity and poor stability.In order to solve the above problems,this study intends to provide an innovative way for the green synthesis of amines by designing new carbon-based non-noble metal catalytic materials.The main contents of this paper are as follows:1.Selective hydrogenation of nitrobenzene as a template reaction,the synthesis process of aniline compounds was discussed.Co@NC/AC catalysts were prepared by impregnation-pyrolysis strategy using bio-based activated carbon as the substrate,and the parameters affecting the catalyst performance were investigated.It was found that the pyrolysis temperature of the catalyst was the key factor affecting its performance,and the catalyst pyrolyzed at 800 °C had the best catalytic performance.The yield of aniline reached 100% under the optimum reaction conditions(1 MPa of hydrogen pressure,110 °C of reaction temperature and 4 h of reaction time),and the activity of the catalyst did not decrease obviously after being recycled for 8 times.Through the substrate extension experiments,we found that the catalyst has good universality for the synthesis of aniline compounds.2.The reductive amination of nitrobenzene and benzaldehyde was used as a template to design non-noble metal catalysts for the synthesis of secondary amines.It was found that the nitrogen-doped graphene nanosheet confined Co catalyst(Co@CN-800)had good catalytic performance for this reaction.The yield of N-benzylaniline was 99.5%,and the catalytic performance was not significantly reduced when the catalyst was used for 5 times.The characterization and control experiments confirmed that the excellent catalytic performance of the catalyst may be due to the synergistic effect of the confined Co-Nx species in the N-doped graphene layer and the mesoporous structure of the catalyst.Catalyst characterization and control experiments confirmed that the robust catalytic performance of the catalyst is probably due to the synergy effect of in situ generated Co-Nx encapsulated in N-doped graphene layer and appropriate meso-pore structure.Through substrate extension experiments,we found that the catalyst can catalyze the synthesis of nearly 20 kinds of secondary amines with high yield,which proves that the catalyst has good universality for the synthesis of secondary amines.