Pretreatment Of Lignocelluloses By Ethanol Solvothermal Method And Fabrication Of Nanocellulose

With the increasing global concern for the development of sustainable energy resources, efficient use of forest resources is also increasing emphasis. The current global focus on biomass refinery of lignocellulose is not only limited to the production of liquid fuels and chemicals but also includes the new type of intermediate products such as nanocellulose. Among the fabrication, nanocellulose is embedded in the plant cell walls that have hierarchical structures and complex compositions, the related phenomenon is called biomass recalcitrance. The process of traditional methods was usually low efficiency and to some degree detrimental to the environment, herein, we propose research ideas and implementation methods to producing nanocellulose with ethanol solvothermal pretreatment followed by ultrasonic nanofibrillation from lignocellulose.This study mainly focused on the effect of the reaction conditions, efficiency and effectiveness by 65% ethanol solvent pretreatment, as well as the synergies of additional treatment with alkaline hydrogen peroxide. Further integration of such pretreatments with ultrasonic disintegration process into nanocellulose. The product and treatment efficacy were evaluated by chemical component analysis,13C CP/MAS NMR analysis,2D-HSQC NMR spectroscopy, gel permeation chromatography analysis, fourier transform infrared spectroscopy, scanning electron microscopy observation, transmission electron microscopy observation, X-ray diffraction analysis, ther mo gravimetric analysis, zeta potenial analysis, UV-vis spectroscopy and mechanical testing. The main results are as follows:(1) The ethanosolv pretreatment will attack the acid-ester bonds of lignin-hemicellulose compounds, dissolve lignin and hemicellulose.97% of the total lignin and 70% of the hemicellulose can be fractionated in a single ethanosolv pretreatment step, and high purity (95%)cellulose can successfully obtained by the subsequent treatment with peroxide, which can remove the rest lignin and one-third of the remanent hemicellulose.(2) The extraction of lignin from the liquor was GS-lignin, in addition, the extracted lignin has low molecular weight(1678-2024g/mol), suggest that the pretreatment can promote the depolymerization of lignin to small molecules.(3) The component of insoluble product was mainly cellulose, the amorphous cellulose degrades during pretreatment, however, the typical crystalline I form of the native cellulose remained, the relative crystallinity index increased to more than 74%, and the thermal degradation temperature increased to more than 300℃.(4) Cellulose nanocrystals with 1-9nm wide and within 500nm long obtained after ultrasonication displayed a similar yield, size, morphology, and crystallinity but had better mechanical properties and thermal stability than those produced by concentrated acid hydrolysis.