Application And Research Of Electrospun PAN-based Carbon Nanofiber-supported Nickel Composite Catalysts In Heck Reaction

Due to its low prices and wide distribution,nickel-based nano-materials have obtained many researchers' attention.Especially,the study of nickel-based materials as catalyst is more extensive.The study of Heck reaction has a long history.Comparing with palladium catalyst,nickel-based catalysts have unique advantage.In this paper,nickel-based carbon nanofibers composite catalysts with good morphology,high catalytic activity and recyclable performance were prepared by electrospinning technology,hydrogen reduction technology and temperature-programmed carbonization technology.The specific researches are as follows:(1)Nickel chloride as nickel precursor was used to prepare NiCl2 nanofibers(NiCl2/NFs)by electrospinning technology.Two kinds of nickel-based carbon nanofiber composites(Ni/CNFs)were prepared by different reduction methods which were high-pressure hydrogen reduction and H2/Ar high-temperature reduction.A series of characterizations were used to analyze the morphology of nanofiber,the size and distribution of nickel nanoparticles and the valence of nickel.The results indicated that nanofiber composites had good morphology and Ni nanoparticles with small size were evenly dispersed on CNFs,and nano-nickel was zero valent face-centered cubic crystal.Finally,the catalytic properties of the composites were investigated for Heck reaction.When carbonization temperature was 500 °C,both catalysts had a better conversion rate in Heck reaction.But compared the catalytic result,it is concluded that Ni(0)/CNFs prepared by high-pressure hydrogen reduction had better catalytic performance.So the high-pressure hydrogen reduction is more suitable for the preparation of catalysts.(2)According to the above research,Ni/CNFs that based on organic nickel salt as nickel source were prepared by the process of electrospinning,high-pressure hydrogen reduction and high-temperature carbonization.The results of SEM?TEM and XPS showed that the morphology of Ni/CNFs were neat and smooth,and nickel nanoparticles with uniform distribution and size was proved to be zero-valent nickel.The results of Heck reaction showed that,comparing with inorganic nickel salt,organic nickel salt as nickel source was more stable,and had better catalytic and recyclable performance.The catalyst also showed a certain ability to expand the substrate.(3)On the basis of organic nickel salt,this part added pore-forming agent(polymethylmethacrylate,PMMA)in order to enhance the catalytic performance furtherly.According to the characterizations of the material,it was confirmed that the prepared nickel-based porous carbon nanofibers catalysts(Ni/PCNFs)had good nanofibers morphology and uniform distributions of nickel nanoparticles.Meanwhile the porous structure was formed and the size of zero valent nickel nanoparticles was about 3 nm.The PMMA effectively overcame the shortcomings of catalyst in the unsatisfactory catalytic performance.In the process of carbonization,PMMA decomposed and formed porous structure on CNFs,which increased the reaction rate and conversion rate.So the Ni/PCNFs further improved the catalytic performance for Heck reaction.In summary,the carbon nanofiber supported nano-nickel composites were prepared by electrospinning,high-pressure hydrogen reduction and high-temperature carbonization process.Nickel-based catalysts with excellent performance can replace noble metal catalysts and be widely used in Heck reactions.The carbon fiber not only can be as metal carrier,carbon has a certain degree of reduction can also further to protect zero-valent nickel nanoparticles.Supported nickel-based catalysts not only show the potential value in the study,but also will also have application value in the industrial industry.