Preparation Of Nitrogen-doped Carbon Supported Palladium-based Catalysts And Its Application

With the rapid development of science and technology,various types ofnano-materials are endless.Precious metal nanoparticles?NPs?,as part of nanomaterials,have also been widely used in energy,chemical,medical and environmental fields.It has an important application value,especially in the field of chemical catalysis.In the practical application,the precious metal NPs in the noble metal nanocatalyst have the high surface energy,surface atomic ratio,and coordination unsaturation,which may result in the agglomeration of NPs and thus lead to the decrease of activity or even inactivate during the catalytic process.Loading precious metal NPs on the carrier can be a good solution to this problem.In addition,carriers usually bring other special properties of the catalyst,such as the material catalytic efficiency,cycle stability and so on due to the support-metal NPs interations.In this paper,three nitrogen doped carboneous support materials,such as nitrogen-doped carbon nanotubes,nitrogen-doped carbon coated iron complexes double-shelled hollow spheres and nitrogen-doped carbon-coated aluminum silicate fibers,were employed as supports to achor Pd NPs or Pd-Fe alloy NPs.The as prepared catalysts were further applied in the organic catalytic reaction to access their catalytic properties,including the activity and cyclic stability.The influence of properties and morphology of the supports and active noble metal NPs on the catalytic performance were also investigated.Our findings provided an alternative way to improve the catalytic performance and stability of the noble metal-base catalysts by introducing heteroatoms to carboneous supports and controlling the morphological of the noble metal NPs.At present,highly efficient supported noble metal catalysts are still desired in catalytic industy.Thereofe,the development of low loading,high catalytic activity and exellent recyclability precious metal catalyst is still a very meaningful work.The main research content is as follows:?1?Develop a new type of composite material?NCT@Pd?by supporting palladium nanoparticles on the surface of nitrogen-doped hollow microtubes and explore its application in organic catalysis.In addition,the particle size of palladium particles supported on the surface of nitrogen-doped hollow microtubes is ultrafine?about 2.3 nm?and uniformly dispersed.Due to the tubular structure,large specific surface area and ultrafine Pd NPs,the obtained NCT@Pd catalysts exhibited good catalytic activity for 4-nitrophenol reduction with a turnover frequency?TOF?of 29.4min^-11 and 44 min^-11 for Suzuki coupling reaction even the metal loading amount is as low as 0.324 wt.%.In addition,catalyst exhibits good cycle stability.?2?A double-shell structured composite material?Fe@NC@Pd?was consructed by using iron complex as inner layer and a nitrogen-doped carbon as outer layer,followed by anchoring Pd NPs on the surface.Furthermore,the resultant magenetic Fe@NC@Pd was utilized in organic catalysis to test its activity and recyclability.Even if the Pd load content is as low as 0.224%,the TOF value of the material in the4-nitrophenol reduction reaction is as high as 354 min^-1,and the material also has outstanding catalytic in Suzuki coupling reaction,and its TOF is up to 52.8min^-1.Besides,Fe@NC@Pd has good stability,and is easy to reusing.?3?A catalytic fiber?ASF@NC/PdFe?was fabricated through wrapping polydopamine on the surface of aluminum silicate fiber with the addition of K₂PdCl₄and FeCl₃,and then annealing in inert atmosphere.The fibrous morphology make it is easy to packed in columns and build a high-performance fixed bed catalytic system.The fibrous morphology make it is easy to packed in columns and build a high-performance fixed bed catalytic system.The results showed that the introduction of trace Fe resulted in a significant increase in catalytic performance compared to the introduction of Pd as a catalytic unit alone.Furthermore,the catalytical fixed bed the system can reduce 2 mM 4-nitrophenol at a flow rate of 200 mL/min and exhibited a good cycle stability and recycability.The fixed bed system is a good solution to the problem of catalyst recovery,and it provides practical prospects for practical industrial applications.