Conversion Of Biomass Into Furan Compounds And Derivatives Diacid

Furfural and 5-hydroxymethylfurfural(5-HMF),are important biomass-derived platform compounds,which can be used as raw materials to produce a series of biofuels and high value-added chemicals.This study was focused on the preparation of highly efficient solid acid catalysts to achive the conversion of biomass such as corn stover and sugars to furfural and 5-HMF.Maleic acid is one of the important chemical materials,which has vital application in the industry.Thus,it is very important to achieve the production of maleic acid from the biomass-derived furfural.The prepared catalysts were analyzed by a series of characterizations,and the effects of reaction parameters on biomass conversion processes were investigated in detail.Furthermore,the reaction mechanism of biomass conversion was also discussed in this study.The main results are as follows:(1)When the homogenous acid was used as catalyst,there was a low furfual yield from corn stover.In order to solve this problem,this study was focused on the preparation of highly efficient solid acid catalyst.The catalyst was prepared from the biomass-derived glucosamine hydrochloride,which was activated by KOH,then,the obtained porous carbon materials(NG-C)was sulfonated with sulphanilic acid and isoamyl nitrite under mild reaction condition.The obtained carbon-based solid acid catalyst(SO3H-NG-C)was used to convert corn stover into furfural and 5-HMF with y-valerolactone as reaction medium.The results indicated that 53%furfural yield(based on the xylose and glucose units in corn stover)and 17%5-HMF yield were achieved under 190℃ for 80 min.Furthermore,the SO3H-NG-C catalyst,with tiny particles,can be separated from corn stover residue easily,which exhibited a good catalytic activity in recycle process and 40%furfural yield can be obtained after three cycles.(2)SO3H-NG-C exhibited the good furfural yield during corn stover conversion processes.However,the tedious processes were need for the preparation of porous carbon support.Then,a simplified preparation method of carbon support was developed with calcium gluconate as carbon sources.The porous carbon support C-GCa-800 was obtained through calcination under high reaction temperature due to the self-template method of calcium gluconate.The sulfonation process could also be optimized by the sulphanilic acid and sodium nitrite,which can be performed under room temperature,then,the solid acid catalyst SC-GCa-800 was prepared successfully.Furthermore,in order to promote the separation of the furfural from solvent,the low boiling point 1,4-dioxane was used as solvent.In view of the highly efficient catalytic activity of SC-GCa-800,the xylose can be transformed into furfural at a relatively low temperature in a range of 100 to 140℃.The high furfural yield of 76.9%was achieved at 140℃ for 40 min.(3)In above studies,the high furfural yiled can be achieved from corn stover with these high acidity solid acid catalysts,however,the general 5-HMF yield indicated that the cellulose fraction in the corn stover was not utilized fully.Therefore,an enzyme mimic solid acid catalyst with binding and catalyzing sites was prepared to achieve the conversion of cellulose and hemicellulose of corn stover into 5-HMF and furfural.During the process of catalyst preparation,the chitosan,p-hydroxybenzenesulfonic acid and o-chlorophenol were used as soft template,-SO3H source and-Cl souce,respectively,which can react with formaldehyde via polymerization reaction to form resin.Comparing with p-hydroxybenzenesulfonic acid formaldehyde resin(S-R),the bi-functional-Cl modified sulfonated resin(Cl0.3-S-R)can improve the 5-HMF and furfural yields from corn stover.And 43.8%5-HMF yield and 38.1%furfural yield were obtained under 190℃ for 80 min in water/1,4-dioxane solvent systems with Cl0.3-S-R as catalyst.(4)Cellulose is connected by glucose units through β-1,4-glycosidic bonds,thus,the cellulose was firstly converted into glucose and which can be hydrolyzed further to 5-HMF.Then,glucose was used as the model compound to achieve conversion of cellulose better in the further study.Furthermore,considering with the isomerization and dehydration are needed in the conversion of glucose to 5-HMF,the bi-functional solid acid catalysts P-SnO2 containing Lewis(SnO2)and Bronsted(phosphate)acidic sites were prepared.A series of phosphate-doped SnO2 catalysts were prepared by varing the addition amounts of phosphates.Moreover,the effects of reaction conditions on glucose conversion were also investigated in detail with P-SnO2 as catalyst.Under optimal reaction conditions,46.4%and 18.9%furfural yields were obtained from glucose with 5P%-SnO2 as catalyst.(5)On the basis of above solid acid catalysts,the high furfual yield can be achieved from corn stover.Then,the biomass-derived furfural was used as substrate to produce maleic acid.A novel lignin-derived porous N-doped carbon material(N-LCK)was developed to transform furfural into maleic acid,and 58%maleic acid yield was obtained at 80℃ in 4 h.Furthermore,the N-LCK catalyst exhibited the good stability during recycle experiments,which has a slight decrease of maleic acid yield after four cycles.The good catalytic performance of N-LCK may be ascribed to the presence of porous structure and N elemental.(6)In order to improve the maleic acid yield further,the novel KBr/g-C3N4 catalyst was developed to catalyze furfural oxidation under water-H2O2 system.The high maleic acid yield of 70.4%was obtained under 100℃ for 3 h.Then,the homogeneous catalysts were used to explore the real activity sites during furfual oxidation,and the results indicated the presence of Br-and base sites are important factors for promoting maleic acid selectivity.Furthermore,the possible reaction pathway of furfural oxidation to maleic acid was proposed on the basis of products analysis and experimental results.