Conversion Of The Hemicelluloses And Lignin In Fast-growing Biomass Into Chemicals

With the development of biorefinery technology,the comprehensive utilization of lignocellulosic biomass has attracted extensive attention.In this paper,the conversion of the hemicelluloses and lignin by-products in the pretreatment process of fast-growing biomass was explored.The high-value conversion of biomass components was realized by converting hemicelluloses and lignin into xylooligosaccharides,phenolic monomers and other chemicals or lignin-based materialsPre-hydrolysis liquor is a waste from the pretreatment of lignocellulosic biomass,which contains large amounts of polysaccharides,oligosaccharides,and monosaccharides derived from hemicelluloses.The saccharides can be degraded into monosaccharides and xylooligosaccharides chemicals by acid and enzymatic hydrolysis to achieve high-value utilization of hemicelluloses.In addition to hemicelluloses,lignin is also by-products of biomass pretreatment.During the pretreatment process,the ?-O-4 skeleton structure of the lignin underwent irreversible "bond break-condensation" reaction,forming industrial lignin with severe condensation and low reactivity.Conversion of industrial lignin into ion-exchange resin,or the catalytic conversion of lignin from lignocellulosic biomass into phenolic monomer chemicals,can not only achieve high-value conversion of lignin,but also conform to the concept of biorefineryHydrothermal pretreatment of lignocellulosic biomass was used to obtain prehydrolysis liquor.The major component in prehydrolysis liquor was xylooligosaccharides,which was achieved according to regulate hydrothermal temperature and time.Results showed that the highest xylooligosaccharides yield(61.69 g/kg)was achieved at 180? for 0.5 h.The solid residue after hydrothermal pretreatment was treated with alkaline ethanol to extract lignin.The structural characterization of the lignin showed that the contents of ?-O-4 linkages decreased with the enhancement of hydrothermal temperature,while the contents of phenolic hydroxyl dramatically increased.The systematic analysis of the extracted lignin structure is contribute to the chemical modification and value-added utilization of the ligninBased on the above research,xylooligosaccharides and monosaccharides were prepared by prehydrolysis liquor obtained from the process of dissolving pulp production.The chemical composition analysis showed that the prehydrolysis liquor contained 47.80 g/L saccharides and 14.10 g/L lignin,which was an ideal raw material for the production of xylooligosaccharides and monosaccharides.Firstly,hemicelluloses and lignin in prehydrolysis liquor were separated by hydrothermal acid hydrolysis method.The xylose yield of 34.82 g/L was achieved with 2.0 wt%sulfuric acid dosage at 120? for 1.0 h,while the lignin was separated as precipitation.Both acid and enzymatic hydrolyses were applied to prepare xylooligosaccharides from prehydrolysis liquor.Results showed that the highest xylooligosaccharides yield of 11.63 g/L achieved when 0.3%sulfuric acid was used at 120? for 2.0 h.The highest xylooligosaccharides yield of 15.65 g/L was observed when using 60 IU/L substrate enzyme dosage at 50? for 6.0 h.Xylobiose and xylotriose were the major products,which accounted for 72.91%of the xylooligosaccharidesBased on the lignin first strategy,Pd/C catalyst,methanol and H2 catalytic reaction system were used to degrade lignin in the biomass into phenolic monomers,resulting in the high value conversion of the lignin.Results showed that the yield of phenolic monomers reached 49.8 wt%when temperature was at 240? for 4 h with 30 atm H2.The solid carbohydrate residue obtained from the catalystic reaction with high retention rate can be further converted into chemicalsThe biorefinery lignin was modified by phenolation and sulfonation,and the modification mechanism of lignin was explored by 2D-HSQC NMR.The lignin-based cation exchange resin was prepared by one-pot method for the adsorption of heavy metal ions in wastewater.It was found that the larger the dosage of sulfonated reagent,the higher the swelling capacity and the S content of the resin.The maximum ion exchange capacity of the resin was 2.26 mmol/g,and the adsorption capacity for Pb(II)reached to 167.2 mg/g.