Study On Extraction And Degradation Of Hemicellulose In Miscanthus

With the depletion of fossil energy and serious environmental pollution,the conversion of biomass has become the focus of attention.Hemicellulose in lignocellulosic as the second largest biomass resources,has great potential for development in the production of fuel ethanol from chemical energy sources.This thesis takes Miscanthus as the research object,analyzes the hemicellulose separation,degradation and fermentation process,and combines chemical analysis instruments to study the chemical composition and structure,which can provide experimental basis for the application of Miscanthus hemicellulose in the field of chemical production.The results are as follows:（1）Ultrasonic assisted alkali method used to study the optimum extraction technology of hemicellulose in Miscanthus.The optimal extraction conditions of hemicellulose were as follows:12%as NaOH concentration,1:20 as the ratio of raw material to liquid,20 min as ultrasonic time,70°C as temperature,3.5 h as reaction time,under these conditions,the yield of hemicellulose was 23.23%,and the purity was 89.31%.（2）The chemical composition,structure and pyrolysis processand of hemicellulose were investigated by elemental analysis,FT-IR,TG-DSC,and so on.It concluded that the structure of hemicellulose was mainly composed of xylose unit as the main chain and glucuronic acid and arabinose as the side chain.The structure is 4-O-methyl-D-glucuronic acid-α-L-arabinose-D-xylan and the molecular formula is(C₃₂H₄₈O₂₇)_n.The result of pyrolysis analysis showed that the pyrolysis process of hemicellulose can divided into four stages:dehydration,main pyrolysis,carbonization and coke gasification.The main process occured the pyrolysis and combustion process of hemicellulose from 125 to 405,and the mass loss accounted the raw material for52.37%.（3）Through the study of hemicellulose degradation,it is concluded that the optimum technologies of acid degradation were 0.5 mol/L as sulfuric acid concentration,1:50 as the ratio of raw material to liquid,2 h as reaction time,100°C as reaction temperature,under these conditions,the saccharification rate was 90.07%.The optimum conditions of enzyme degradation were 15 min as activation time,45°C as activation temperature,1:140 as the ratio of raw material to liquid,7 h as reaction time,under these conditions,the saccharification rate was 72.53%.（4）Through the study of hemicellulose fermentation to produce ethanol,it is concluded that the optimum conditions of the fermentation were 8%as yeast dosage,4d as fermentation time,20 mL as yeast volume,1%as ammonium sulfate concentration,2.5%as glucose concentration,10 mL as the volume of ammonium sulfate,2 mL as the volume of the medium,under these conditions,the ethanol content was 1.52 mL/g.The conversion rate of total reducing sugar was 70.94%.