Development Of Heterogeneous Catalysts Based On Cellulose And Chitin And Their Catalytic Performance Research

Cellulose and chitin are natural macromolecule polymers with similar monomer structures.They are the two most abundant renewable resources in nature.They have the advantages of wide distribution,abundant reserves,cheap,easy availability,and sustainable renewability.It has important applications in textile,papermaking,medicine,breeding and other fields.In addition,because these two natural biomass materials contain a large amount of carbon and oxygen elements,especially chitin is also rich in nitrogen element,they can be used to prepare functional carbon materials with a large specific surface area for adsorbing heavy metal ions and organic pollutants in water,or used as a support for heterogeneous catalysts or catalyst active components.In view of this,this paper makes full use of the characteristics of these two natural biomasses and uses them as a support for the active components of the catalyst to synthesize a supported catalyst with higher catalytic activity and target product selectivity,which achieves the selective hydrogenation of phenolic compounds and nitriles under mild conditions.Besides,phytic acid derived from biomass was also introduced to synthesize phosphorus-containing functional carbon materials with cellulose as raw material to realize the oxidative coupling reaction of benzyl amines.The main findings are as follows:(1)With natural biomass cellulose and phytic acid as raw materials,a cellulose-phytic acid gel mixture can be obtained by simple heating and stirring,and then carbonized in a muffle furnace to obtain a phosphorus-doped functional carbon material with a high specific surface area 1751 m~2/g.Studies have found that the flame-retardant properties of phytic acid prevent cellulose from being burned when carbonized in the muffle furnace,thereby creating a functional carbon material with a larger specific surface area.In the oxidative coupling reaction of benzylamine,the phosphate group and the carbonyl group in the carbon material were its catalytic centers.(2)A supported Pd Ni bimetallic catalyst was prepared using natural cellulose as a support to realize the selective hydrogenation of nitriles into secondary amines.The abundant oxygen-containing functional groups on the cellulose can sustain a high degree of dispersion of the bimetal during the reduction process.The presence of Pd promotes the dispersion of Ni species,and the presence of Ni promotes the increase of the crystallinity of Pd.The original structure of cellulose maintains during the reduction process of catalyst.Experiments show that the synergistic effect of Pd and Ni promotes the highly selective conversion of benzonitrile to secondary amine.This research opens up the application of natural biomass materials in the field of heterogeneous catalysis.(3)A supported Pd catalyst was prepared using natural biomass chitin as a support,which realized the selective catalytic hydrogenation of phenol to cyclohexanone in aqueous solution.The nitrogen-containing and oxygen-containing functional groups in chitin promote the Pd species to maintain a highly dispersed state.The appropriate reduction temperature can not only ensure the reduction of the Pd species,but also keep the original structure of the chitin from being destroyed.The strong coordination between Pd nanoparticles and the oxygen-containing groups of chitin makes the Pd firmly anchored on the surface of the chitin,so that the catalyst maintains good cycle stability during the catalysis process.Loose features of the catalyst enable it to be made into a catalyst monolithic column to achieve the continuous progress of the phenol selective transfer hydrogenation reaction under liquid phase conditions.