Study On Pretreatment And Resource Utilization Of Lignocellulose Based On Ammonia Fiber Expansion

Fossil energy is becoming increasingly depleted and its utilization has raised a series of environmental problems.Therefore,renewable resources such as lignocellulosic biomass,which can be converted into clean energy,are widely concerned.The special structural characteristics of lignocellulosic biomass make it recalcitrant,and pretreatment is an important step in converting lignocellulosic biomass into biofuels.In this work,two combined pretreatment methods were developed to improve the enzymatic saccharification efficiency and biohydrogen（H₂）yield of biomass as well as to extract regenerated lignin using lignocellulosic biomass such as P.sinese,oak and camphor wood as feedstock.It mainly includes:AFEX combined with NaOH pretreatment method to improve the pretreatment efficiency and enzymatic saccharification efficiency of lignocellulosic biomass and used for dark fermentation to produce H₂;AFEX assisted low eutectic solvent（DES）pretreatment method to analyze its effect on the fraction and enzymatic efficiency of giant mycorrhiza,and detailed analysis of the structure and composition of regenerated lignin.The main research of this article is as follows:（1）In this study,the effects of AFEX combined with NaOH（A-NaOH）pretreatment on the properties of P.sinese（herbaceous）,oak（hardwood）and camphor（softwood）were evaluated by lignin removal and enzymatic digestion efficiency analysis.The results showed that the lignin removal rate was 84.2%,58.4%and 35.6%,and the enzymatic efficiency was 51.02%,18.74%and 13.56%for giant mycorrhiza,oak and camphor wood,respectively,under 4%A-NaOH conditions.The lignin removal rate and enzymatic efficiency were significantly higher.A-NaOH pretreatment method was more effective for herbaceous biomass than for woody biomass such as hardwood and softwood.（2）Effect of AFEX combined with NaOH pretreatment on hydrogen production from dark fermentation in lignin biomass at high temperatures（medium（37°C）and high（55°C））.The results showed that A-NaOH pretreatment significantly increased the dark fermentation bio-H₂ production from P.sinese,oak and camphor wood.The H₂ yields under medium temperature conditions were 152.3,99.1 and 76.9 m L/g TS,respectively,which were 1.70-2.38 times higher than those of the untreated group.The H₂ yields under high temperature conditions were 99.96,69.98 and 55.30 m L/g TS,respectively,which were 1.53-1.98 times higher than those of the untreated group.In the medium and high temperature dark fermentation systems,the abundance of thick-walled phylum（Firmicutes）in the pretreatment group was 1.14-1.19 and 1.24-1.38 times higher than that in the untreated group,respectively.The H₂ production during medium-temperature dark fermentation was higher than that of high-temperature fermentation,and the energy consumption was low.These results suggest that A-NaOH pretreatment is an effective method to utilize lignocellulosic resources.（3）Effect of AFEX-assisted DES pretreatment method on the enzymatic efficiency of lignocellulosic biomass and regenerated lignin.Two DESs,DBU:LA（LADES）and DBU:PEG（PEGDES）,were first synthesized to pretreat AFEX-treated P.sinese.After AFEX-assisted LADES and PEGDES treatment at 120°C for 4 h,the lignin removal rate of giant fungus grass was 37.99%and 91.81%,cellulose recovery was 78.48%and90.81%,and enzymatic efficiency was 54.54%and 82.54%.The polydispersity coefficient of P-Lignin was 1.28 and the elemental content of S was 0.02 by gel permeation chromatography and elemental analysis,which were more homogeneous and less toxic than those of A-Lignin and L-Lignin,contributing to the development of downstream lignin products.2D-HSQC NMR results indicated that all three lignins were of G-S-H type.