Study On The Extraction Process Optimization And Reaction Kinetics Of Hemicelluloses From Eucalyptus Prehydrolyzate

Hemicelluloses are abundant natural biological polymer on earth,and an increasing bio-refining research work has been done to make full use of hemicelluloses in plant fiber material and the technology of hot water pre-hydrolysis is widely used.Eucalyptus is rich in hemicelluloses,the study of its high value utilization is of great significance to biomass resources and sustained development of pulp and paper industry of our country.Thus,in this paper,hot-water pre-hydrolysis was conducted to extract the hemicelluloses of Eucalyptus before pulping.Then the effects of the pre-hydrolysis conditions on the main components in prehydrolyzates and prehydrolized wood.Moreover,the structure of hemicelluloses obtained from Eucalyptus pre-hydrolysis was characterized,kinetic model analysis of hemicelluloses hydrolysis in Eucalyptus for xylose production was studied,which may be applied as theoretical basis and technical support for Eucalyptus pulp and papermaking integrated biomass refining.The hemicelluloses of Eucalyptus wood chips was extracted by pre-hydrolysis.The different paramaters,such as prehydrolysis temperature,retention time and liquor to wood ratio,initial pH value,were evaluated their effects on the hemicelluloses of Eucalyptus by hot-water pre-hydrolysis,measured by main components in prehydrolyzates and prehydrolized wood,and using P-factor to optimize the pre-hydrolysis process conditions.If the xylose mass concentration is considered,the optimal pre-hydrolysis process is under prehydrolysis temperature 170?,retention time 105min,P-factor 1144,liquor to wood ratio 1:8,the initial pH value 4.00.The structure of hemicelluloses obtained from Eucalyptus pre-hydrolysis was characterized using the high performance liquid chromatography?HPLC?,thermogravimetric analyzer?TGA?and Fourier infrared spectrometer?FT-IR?,two-dimensional nuclear magnetic resonance?NMR?.The main component of Eucalyptus pre-hydrolysis is hemicelluloses,and it contains typical xylan-based hemicelluloses with acetyl and glucuronic groups.The reaction process of pentosan in Eucalyptus pre-hydrolysis was studied.In the process of Eucalyptus pre-hydrolysis,the pentosan hydrolysis can be divided into two stages:the pentosan mass dissolution stage and the pentosan residual dissolution stage.The reaction kinetic equation was established,and the relationship between the rate constant k₁ and the prehydrolysis temperature T in the hydrolysis process of Eucalyptus hemicellulose was obtained as follows:lnk₁=-8734.321/T+17.88,and the activation energy of xylose was 72.62 KJ/mol.