Research On The Preparation Of Highly-Dispersed Nanometal Heterogeneous Catalysts And Their Applications In Hydrogenation Reactions

Highly dispersed metal nano-heterogeneous catalysts have attracted much attention due to their excellent catalytic performance and high stability,and have also been widely used in practical industrial production.The preparation of highly dispersed,highly active and highly stable catalysts has become a hot topic of research in recent years.In this paper,a series of highly dispersed cobalt catalysts were prepared by the hard template sacrificial method,and high-dispersion metal palladium catalyst was prepared by employing carbon nitride and graphene complex as supports.A series of highly-dispersed metal catalysts prepared for the hydrodeoxygenation of lignin derivatives,(transfer)hydrogenation of nitro compounds have been studied.1 A hard-template sacrificial method was employed to fabricate atomically dispersed Co catalyst,Co(NO3)2·6H2O-glycine was employed as the precursor,three kinds of silica templates with different microstructure(MCM-41,SBA-15 and FDU-12)were employed.The impact of pore structure of the templates on the dispersity of Co was investigated.The catalysts fabricated with different template presented different Co dispersity,leading to distinguishing catalytic performance.Compared with the catalyst prepared via MCM-41 and FDU-12,the optimized Co1@NC-(SBA)catalyst with atomically dispersed Co displayed outstanding catalytic activity for the hydrodeoxygenation(HDO)of lignin-derived species as well as the hydrogenation of various nitro-aromatics.The catalytic performance of Co1@NC-(SBA)for the HDO of vanillin and the hydrogenation of nitro compounds exceeded most of the currently reported non-noble metal catalysts After ten continuous runs,the conversion and selectivity of p-nitrochlorobenzene kept at 94%and 94%,respectively.The outstanding catalytic acticity and stability were attributed to the atomically dispersed of Co,the unique Co-Nx structure and the excellent pore structure.2 We employed SBA-15 and 1,10-phenanthroline(Phen)as hard template and ligand,respectively.The Co(NO3)2·6H2O-Phen precursor was transformed into the pores of SBA-15,highly dispersed Co catalyst CoN@PCN was obtained after carbonization followed by alkali leaching by a sacrificial-template pyrolysis strategy.The CoN@PCN displayed excellent catalytic activity and selectivity for the hydrogenation of nitroarenes with ammonia-borane as hydrogen donor.The reserche showed that Co was anchored on the support by bonding with pyridinic N.The outstanding catalytic performance of the prepared CoN@PCN was strongly associated with its ultra dispersed Co-Nx active sites,high adsorption ability of the catalyst for ammonia-borane,large surface area and well-defined mesopouous structure.3 Layered C3N4 polymer/graphene hybrid(CNNS/rGO20)was fabricated by a hydrothermal method followed by loading Pd nanoparticles on the hybrid.The obtained heterogeneous catalyst was used for the transfer hydrogenation of a series of nitro-compounds to give the corresponding aromatic amines with outstanding activity by employing formic acid as hydrogen donor.Compared with C3N4 nanosheets and rGO,CNNS/rGO20 with heterostructure presented higher BET surface area,richer channel structure as well as higher dispersity of palladium,leading to higher catalytic activity.The results showed that the prepared catalyst has good catalytic activity for the catalytic transfer hydrogenation of a series of aromatic nitro compounds.Under mild conditions(25?,ethanol/water:1:1),a series nitro compounds can be converted into corresponding aromatic amines with high conversion as well as selectivity.