Liquefaction Mechanism Of Eucalyptus Woodchips And Its Main Components In Water And Tetralin

In this thesis,cellulose and lignin were extracted directly from eucalyptus woodchips(EW).The effects of temperature,reaction time and solvent on the liquefaction efficiency of EW and its main components were studied in water and tetralin,respectively.The compositions of liquid,solid and gas products were analyzed,ethe liquefaction mechanism of cellulose,lignin and EW were discussed.In hydrothermal liquefaction process,cellulose was firstly hydrolyzed to glucose and fructose,and 5-Hydroxymethyl furfural(5-HMF)was produced by dehydration of glucose and fructose.And then phenols and ketones were formed by ring opening,hydrolysis,dehydration and isomerization of 5-HMF.Lignin was hydrolyzed into several guaiacyl and syringyl phenols(primary products),and then these primary products became ethers and other phenols through the ether and C-C bond cleavage,and furthermore reactions e.g.isomerization,methylation,decarbonylation.In the process of hydrothermal liquefaction of EW,cellulose and lignin were simultaneously decomposed.Cellulose and hemicellulose were decomposed at a lower temperatures(<240?)in a shorter reaction time,and decomposition of lignin was enhanced at higher temperature(>240?)and in a longer time.In tetralin liquefaction process of cellulose,methyl free radicals,furfural,and CO were produced from pyrolysis and hydrogenolysis of cellulose.Aromatic hydrocarbons in liquid product were formed by coupled reaction between methyl radical andtetralin and naphthalene.Phenols in products were produced by alkylation and pyrolysis of three-hydroxyl phenols that likely derived from isomerization of furfurals.In tetralin liquefaction process of lignin,lignin was firstly pyrolyzed and hydrogenolyzed to guaiacyl and syringyl phenols which had no carbonyl group in side chain,and then methoxy groups on these phenol structure were reduced to hydroxyl groups and thus produced polyhydroxyl phenols.Phenol products partly were methylated to produce ether compounds.The products of tetralin liquefaction of EW included some components dereived from liquefaction of cellulose and lignin,and some components from side reaction of tetralin,indicating tetralin liquefaction of EW involving a complex mechanism.