Study On Effects Of Combined Pretreatments Of Hydrothermal Treatment And Chemimechanical Refining On Enzymatic Hydrolysis Of Poplar

It is of great significance to utilize abundant biomass for biorefinery to produce biofuels,which can help to alleviate the energy crisis and environmental problems.However,the resistance of biomass to enzymes is the main bottleneck that limits the saccharification yield of enzyme hydrolysis.Therefore,it is necessary to use appropriate pretreatment to break the stubborn resistance of biomass.In this study,the poplar wood chips were used as raw materials,the effect of combined pretreatments of hydrothermal treatment and chemimechanical refining on the enzymatic hydrolysis efficiency of poplar was studied,and the effect of this combined pretreatment on characteristics of poplar substrate was studied.(1)The effects of different hydrothermal pretreatments on the main components’changes in hydrolysate and wood chips were studied.The results showed that,with the increase of hydrothermal pretreatment intensity,the dissolving-out contents of sugars,lignin and acetic acid in the hydrolysate increased,and the dissolving-out content of xylose increased obviously.With the increase of hydrothermal pretreatment intensity,the yield of poplar wood chips decreased,the xylose content in poplar decreased,but the change of lignin and glucose content was not obvious.(2)The effects of combined pretreatments of hydrothermal and mechanical refining on enzymatic hydrolysis of poplar wood chips were studied.The results showed that the enzymatic hydrolysis efficiency of poplar substrate after different hydrothermal pretreatment was 1.25-1.72 times higher than that of without hydrothermal pretreatment.When CHF was 130.59,the glucose conversion rate and concerntion reached 71.58%and 17.28 g/L,respectively.Compared with the control,the glucose conversion rate and concerntion increased by 73%and 135%,respectively.(3)The effects of three different chemical impregnations on enzymatic hydrolysis efficiency and characteristics of poplar were studied.The results showed that,1)the combined pretreatment of hydrothermal,alkaline peroxide and mechanical refining can improve the enzymatic hydrolysis efficiency of poplar substrate.The optimal loading was 3%NaOH and 3%H2O2,and the glucose conversion and concentration increased by 25%and 23%,respectively;2)the combined pretreatment of hydrothermal,alkaline sulfite and mechanical refining can improve the enzymatic hydrolysis efficiency of poplar substrate.The optimal loading was 3%NaOH and 4%Na2SO3,and the conversion and concentration of substrate glucose increased by 27%and 24%,respectively;3)the combined pretreatment of hydrothermal,Fenton and mechanical refining can effectively improve the enzymatic hydrolysis efficiency of poplar substrate.When the molar ratio of ferrous sulfate to hydrogen peroxide was 1:90,the enzymatic hydrolysis efficiency was the highest in the study,and the glucose conversion and concentration are increased by 30%and 19%,respectively.Three different types of pretreatments showed different effects on the composition and characteristics of the substrate.The combined pretreatment of hydrothermal,Fenton and mechanical refining had a greater effect on the specific surface area and fiber fines content of the substrate than the other two kinds of impregnation methods,but had less effect on water retention value and surface lignin concentration.Under the optimum conditions,taking the glucose conversion rate as the evaluation standard,the ability of three different chemical impregnation methods to improve the enzymatic hydrolysis efficiency of poplar substrate was in the following order:Fenton>AS>AP.(4)The effects of the combined pretreatment of hydrothermal,Fenton and mechanical refining on the enzymatic hydrolysis efficiency and characteristics of poplar substrate were studied.The results showed that after the combined pretreatments of hydrothermal,Fenton and mechanical refining,the highest glucose conversion and concentration reached 92.40%and 20.28 g/L,respectively.The combined pretreatment of hydrothermal,Fenton and mechanical refining further changed the characteristics of the poplar substrate,increased the specific surface area,water retention value,and fines content of the of poplar substrate,and reduced the surface lignin concentration.