In Situ Preparation Of Magnetic Functionalized Carbon Nanotubes To Support Palladium As A Catalyst For The Heck Reaction

In current production,Heck reaction has been widely used in the production research fields of organic medicine and natural product synthesis due to its important c-c bond synthesis.Its traditional homogeneous catalyst has high catalytic performance,but due to the high cost,can not be recycled,easily to waste and other disadvantages,which greatly limits its large-scale application.Heterogeneous catalysts can effectively improve the above shortcomings,but there are still some problems in the reaction,such as the phenomenon that the active components are easy to leach and aggregate,which leads to the decline of the activity and the difficulty of catalyst recovery.Therefore,in order to solve these problems effectively,the active component nanoparticles can be highly dispersed and fixed on the magnetic material to synthesize the magnetically recoverable catalyst.On the one hand,in order to improve the dispersion of active components and prevent the catalyst in the reaction falls off or reunion,the surface of magnetic materials has been functional,which can maintain good catalytic activity,on the other hand,after the reaction,it can be recycled by simple magnetic,at the same time it can also reduce the catalyst loss,energy consumption,and production time.However,in the preparation of magnetic nanocatalysts,in order to improve the surface dispersion efficiency and possess magnetism,the preparation process of the magnetic carrier is often very complicated.Carbon nanotubes are widely used in catalyst preparation because of their large specific surface area,good conductivity and chemical stability.In this paper,the onestep in-situ preparation of doped oxygen and nitrogen magnetic carbon nanotubes was carried out by a series of methods such as water vapor deposition,and its catalytic performance was tested by applying the load of the active component Pd to the Heck reaction.According to the growth mechanism of carbon nanotubes,a catalyst containing the magnetic metal Ni was designed and prepared for the preparation of carbon tubes,during the growth of carbon tubes,the Ni metal was sucked into the tube due to the capillary effect to make the tubes magnetic.At the same time,precursors containing O and N elements were introduced into the process of the growth of carbon tubes,so that various active groups were uniformly formed on the surface of carbon tubes.Through a series of experimental characterization and the analysis of DFT theoretical calculation,due to the low adsorption capacity of these active groups with the active metal Pd nanoparticles,they have stronger stability and dispersibility when the Pd nanoparticles are loaded and dispersed,so the catalyst shows better catalytic activity and stability.Furthermore,we selectively prepared carbon tubes with different N element groups(pyridine N,pyrrole N,etc.),and analyzed the effect factors of different groups on the loading of Pd and the reaction by experimental and theoretical calculation,so as to infer the action mechanism of doped groups in catalyst preparation and reaction.These results will be of great significance for the design of highly effective magnetic catalysts for other reactions.