In-situ Synthesis Of Metal-embeded Porous Carbnon Sphere And Their Performance Of The Catalytic Hydrogenation

Carbon-based metal materials are widely used in the fields of electrodes,energy storage,catalysts and adsorbents,and have received constant attentions from the academic and industrial communities.The uniform distribution,controllable dimensions,adjustable morphology and thermal stability of metal nanoparticles on the surface of carbon materials have been the focus of research on preparation of the carbon-based metal materials.However,the physical structure of the carbon material and the interaction between the metal particles and the carbon carrier,and the preparation methods have a significant influence on the structure and properties of the metal particles.For example,carbon-loaded noble metal catalysts generally have defects such as poor reproducibility and unstable catalytic performance due to the influence of the raw materials and synthetic processes.Generally emerging synthetic carbon materials require further strong acid/alkaline etching before loading metals because of the lack of metal nanoparticle anchors,but this process is environmentally unfriendly.In addition,the interaction between carbon and metal particles is weak,which lead catalysts prone to metal particles agglomeration and catalyst deactivation.Based on the St?ber method,this paper innovatively proposes a one-step method for the in-situ synthesis of porous carbon sphere catalysts with surface-embed metal particles,which is driven by the interaction between the phenolic polymer and metal ions and the continuous expansion of the molecular chain during the condensation process.During the carbonization process,the reduction and crystallization of metal ions and anchoring of particles are completed.The metal particles prepared by this method are partially embedded on the surface of the carbon sphere,which limits the surface migration of the particles and avoids metal agglomeration,which greatly improves the thermal stability of the catalyst.At the same time,the metal particles are evenly distributed on the surface of the carbon sphere that improves the utilization of the metal.The catalytic performance of nitrobenzene is studied by catalytic hydrogenation to aniline.The main conclusions and results of this article:（1）Under acidic conditions,the hydrothermally synthesized mother liquor pH has a significant effect on the morphology and metal dispersion of Pt@CS.Under acidic conditions,the spherical morphology of the carbon prepared is randomly shaped and the metal particles are dispersed unevenly.Especially at pH of 4.5 no phenolic resin polymer can be formed.（2）In the alkaline environment,when the more ammonia and ethanol are added to the hydrothermally synthesized mother liquor,the smaller the carbon sphere particle size becomes.When the molar ratio between formaldehyde and resorcinol is increased,the carbon sphere particle size gradually large.In addition,the amount of ammonia also has a significant effect on the distribution and particle size of the metal particles.（3）During the in-situ hydrothermal synthesis,Pd is present in the form of Pd²⁺,and the SP² and SP³ carbons are mixed and shifted.However,in the subsequent carbonization process,as the carbonization temperature increases,Pd²⁺is gradually reduced to Pd;adding a metal precursor solution in different stage of the phenolic polymerization will have a significant effect on the size of the metal particles.As the degree of polymerization deepens,the size of the resulting metal particles increases;（4）Under the optimized conditions,the surface inlay metal particle porous carbon sphere catalyst was prepared by the in-situ alkali synthesis method,and the palladium particles were embedded on the surface of the carbon sphere,and the carbon sphere-loaded palladium catalyst was highly dispersed and uniform in size.At a temperature of 25°C and a pressure of 1.0 MPa,the conversion was 100%.Repeated application of Pd@CS-13 catalyst 15 times still has high catalytic activity...