Conversion Of Cellulose To 5-hydroxylmethylfurfural Catalyzed By Metal Salt In Ionic Liquid

Biomass,is one of the most abundant renewable resources in nature,whose efficient conversion and utilization is of great significant for easing the resource shortage problem caused by the exhaustion of fossil fuels,and the research on the transformation and utilization of biomass has been attracting much attention.5-hydroxymethylfurfural?HMF?,as an important chemical platform compound which can be directly converted from biomass cellulose,contains lively functional groups in its intramolecular and can be transformed into different chemicals by different derivatization reaction,such as:oxidation,reduction,esterification,condensation et al.However,cellulose is insoluble in most of organic solvent,which has become a major problem for cellulose utilization.Since ionic liquid as a green chemical solvent was found to be able to dissolve cellulose efficiently,it has been widely used in the study of cellulose conversion.In this study,Metal chloride salts were used as catalyst to directly convert cellulose into HMF in[Bmim]Cl under oil-bath heating,in order to provide guidance and reference for the efficient and low-cost production of HMF.Firstly,single CrCl₃ and its composite catalyst with other metal salts?such as:FeCl₃?CuCl₂?AlCl₃?MnCl₂ and SnCl₄?were used to directly convert cellulose dissolved in[Bmim]Cl into HMF,and based on HMF yield and solid residue yield over time,the effects of different catalysts on different stage of cellulose degradation were investigated and the best catalyst was selected.The experiment results show that CrCl3-AlCl3 was found the most effective catalyst which resulted a high HMF yield of 58.3%in 3h,which was reduced nearly 1/3 compared to single CrCl₃ when both HMF yields were similar.The main reason was suggested that the decomposition rate of cellulose can be significantly accelerated by AlCl₃,while the conversion of glucose to HMF can be accelerated by CrCl₃,thus the whole reaction is accelerated.Besides,according to the characterization of the solid residue after the reaction,the formation mechanism of humins was confirmed again that humins was formed by the polymerization of HMF and fructose dehydrated intermediates.In addition,the effects of the species and amount of catalyst,temperature,atmosphere,amount of cellulose,polymerization degree of cellulose,reaction scale on the degradation of cellulose with CrCl₃-AlCl₃ in[Bmim]Cl heated by oil bath were investigated in detail.Results show that the highest HMF yield of 59%was obtained at 120?in 10g[Bmim]Cl for 4h with 0.5g cotton and 25 mol%-2.5 mol%CrCl₃-AlCl₃ under N₂?dry?atmosphere.CrCl3-AlCl3 can be used to convert natural biomass cellulose with higher polymerization degree into HMF,which can greatly shorten the reaction time and improve the yield of HMF.Besides,Water plays an important role in cellulose degradation,although it can promote the decomposition of cellulose,it also inhibits the dehydration of fructose and promote the side reactions of HMF.Therefore,the amount of water in system must be reasonably controlled to ensure that it can promote the decomposition of cellulose while its negative effects can be reduced.