Preparation And Performance Investigation Of Modified Polyacrylonitrile Supported Pd-based Nanoparticles Catalysts

In the past decades,the widespread use of traditional fossil fuels has led to serious environmental and energy problems,and countries around the world have conducted a lot of research on renewable and clean energy.Because of its high energy density,abundant reserves and environmental sustainability,hydrogen has become an ideal clean fuel.However,finding innovative materials with high hydrogen storage/release capacity is one of the biggest challenges for the widespread adoption of a hydrogen economy,as hydrogen is extremely low in density in the air and is at risk of explosion in gaseous storage and transportation.Formic acid?FA?is a safe and efficient liquid phase chemical hydrogen storage material?hydrogen content up to 4.4 wt%?,which can release hydrogen on demand under mild conditions,and has a broad application prospect in the development of portable hydrogen fuel cells.The preparation of catalyst for dehydrogenation of formic acid with good catalytic performance and stability by optimizing the support material and the active metal is a hot topic.In this paper,polyacrylonitrile?PAN?was chemically modified to prepare amidoxime polyacrylonitrile?AOPAN?beads,which were used as polymer carrier to support Pd and other transition metals to catalyze hydrogen production from formic acid,and a series of studies were conducted on the performance of the catalyst.The main contents are as follows:1.Use of hydroxylamine hydrochloride and the modification of PAN,got together the AOPAN solution,using N,N-dimethyl formamide hydrophilicity was prepared through solvent release process of millimeter AOPAN beads.After adsorption of metal ions by amidoxime group,palladium?Pd?supported nanoparticles catalyst?Pd/AOPAN?was prepared.In the case of no other additives,the low temperature catalytic decomposition of HCOOH produces hydrogen to study the performance of the catalyst,through optimizing the load of Pd,the obtained catalyst had good catalytic activity(TOF value up to 1285h^-1)and recovery?catalytic activity remained good after five times of reaction?in the catalytic hydrolytic reaction of formic acid under mild conditions.In addition,the action mechanism of the catalyst was further discussed by using a variety of physical and chemical characterization methods.2.With AOPAN beads as the support,the transition metal particles such as cobalt?Co?,nickel?Ni?and so on were successfully loaded onto AOPAN beads with the fixed Pd load unchanged,and the bimetal Pd-based nanoparticle catalysts?PdCo/AOPAN,PdNi/AOPAN?were prepared.The catalytic hydrolysis of formic acid was used to study the performance of the catalyst.Under the condition of 50?and no other additives,the TOF value of the prepared catalyst can reach up to 4291 h^-1,and it still had excellent catalytic activity after 5 cycles,showing good stability and recyclability.Through a variety of characterization after test and analysis,presumably AOPAN load Pd catalysts excellent catalytic performance mainly depends on strong coordination ability of the groups together amine oxime,in the process of reaction can reduce the leaching of Pd,Co,Ni nanoparticles or reunited,the other carrier cyano in stabilizing and distribution on the surface of the metal nanoparticles plays a key role,may also participate in FA dehydrogenation synergistic activation.