Synthesis Of Nitrogen Doped Carbon Materials And Their Application In Catalytic Reaction

Porous carbon materials are widely used in the fields of catalysis,adsorption and electrochemistry due to their unique properties.In the catalytic field,porous carbon often acts as the carrier of metal catalysts because of its rich pore structure,excellent conductivity and thermal conductivity,and chemical inertia.For pure carbon carriers,there are problems of metal agglomeration and loss,which will reduce the catalytic activity and service life.Therefore,improving the synthesis technology to achieve high dispersion and strong stability of the metal catalyst is the key to improving the performance of the catalyst.The development of nitrogen-doped porous carbon provides the possibility to solve this problem.The nitrogen-containing fine structures can become solid coordination of the metal and can inhibit the agglomeration behavior of the metal.The aim of this paper is to synthesize nitrogen-doped porous carbon materials with high specific surface area and high nitrogen content as support for palladium catalyst.It is expected to synthesize highly dispersed and stable carbon/palladium catalysts by optimizing the preparation process,and to be used in the aerobic oxidation of benzyl alcohol and styrene under mild conditions.Firstly,ordered mesoporous carbon materials were synthesized by simple hydrothermal self-assembly strategy using resorcinol-formaldehyde resin as precursor,F127 as structure-directing agent and melamine as nitrogen source.Compared with the traditional disordered porous carbon,the porous carbon samples has long-range ordered hexagonal channels,higher specific surface area and pore volume.The effects of reactant ratio and carbonization temperature on the structure and composition of porous carbon were investigated.With the increase of carbonization temperature,the orderliness and specific surface area of porous carbon materials are improved.However,when the temperature is too high,the pore collapse will leads to the decrease of orderliness.The addition of more melamine increased nitrogen content,but also weakened the orderliness of porous carbon.Then,the highly dispersed Pd/NOMCs nanocatalysts were prepared by adsorption-reduction method using the nitrogen-doped ordered mesoporous carbon as the carrier,and their catalytic activity was tested in the solvent-free aerobic oxidation of benzyl alcohol.The optimum preparation process was explored by changing carrier,changing palladium loading,optimizing reaction temperature and time.The results showed that the conversion of benzyl alcohol and the selectivity of benzaldehyde were24.63%and 85.71%respectively when 1Pd/NOMC-0.3-750 was used as catalyst and reaction temperature was 160?for 3 h.In addition,the conversion of benzyl alcohol decreased slightly in the five cycles,which indicated that the catalyst has high cycle stability.Nitrogen-doped porous carbon materials were synthesized by direct pyrolysis using poly-ionic liquid PCMVImTf₂N containing cross-linking groups as carbon and nitrogen sources.Cross-linking groups can form carbon-nitrogen polymers with high thermal stability in the middle temperature range of 350-400?.Porous carbon with a specific surface area of 581 m²/g can be obtained by carbonizing PCMVImTf₂N directly.Its nitrogen content is as high as 13.85 at.%,and it has microporous and mesoporous hierarchical structure.After adding F127,it can form more mesopores after pyrolysis at high temperature,and the specific surface area is up to 903 m²/g,but the nitrogen content also decreases.The nitrogen-doped porous carbon surface was loaded with a palladium metal catalyst for aerobic oxidation of styrene,and the effects of Pd concentration,reaction temperature and time on the reaction were investigated.The selectivity of benzaldehyde can be improved by increasing Pd concentration or decreasing reaction temperature.The conversion of styrene was 98.21%and the total selectivity of benzaldehyde and styrene oxide reached 80.56%after 14 hours catalyzed by Pd/PNPC-2at 80?,which showed high cyclic stability in cyclic experiments.