Study On Preparation Of Bio-Oil By Direct Liquefaction Of Bagasse In Water-Tetralin Mixture

In this thesis, the liquefaction characteristics of bagasse were studied in a batch-type autoclave with water, tetralin and water-tetralin mixed solvent (WTMS) as liquefaction medium, respectively. The effect of mass ratio of bagasse to solvent, liquefaction medium, the mass percentage of tetralin in WTMS, liquefaction temperature, residence time and alkali-soaking pretreatment of bagasse on liquefaction efficiency were investigated by single-factor experiment and L16 (45) orthogonal test. The results show that conversion from WTMS (tetralin content:50%) liquefaction was 86%, and was higher than those from liquefaction in water or tetralin at the same temperature as temperature increased from 250 to 300℃. These indicate that the synergic effect between water and tetralin exists. The sequence of factors on liquefaction efficient of bagasse is:NaOH dosage in pretreatment> reaction temperature> tetralin concentration in WTMS> mass ratio of bagasse to solvent> residence time. The optimal conditions were:liquefaction temperature 270℃, residence time 30 min, mass ratio of bagasse to solvent 1:6, NaOH dosage 4%, tetralin concentration 50%. The conversion rate of bagasse was 97.9% under above conditions.The GC-MS analysis of heavy oil (HO) showed that HO from water liquefaction contained mainly phenols and ketones; HO from tetralin liquefaction contained mainly aromatic compounds, acids and phenols; HO from WTMS liquefaction contained mainly phenols, acids and ketones. The products distribution in HOs obtained in different solvents had been affected by alkali-soaking pretreatment of bagasse. The elemental analysis of HOs shows that the carbon content and the heat value were improved significantly, and the oxygen content decreased via liquefaction process regardless of whether raw materials was alkali pretreated or which type of solvent was used. The heating value of heavy oil from liquefaction of the NaOH-pretreated bagasse in WTMS is 34.94 MJ·Kg-1.The thermogravimetric analysis of solid residue shows that the solid residues obtained at 280-300℃ in different solvents mainly contained lignin and solid product with high thermal stability. This indicates that cellulose, hemicellulose and a part of lignin have been decomposed in liquefaction process of bagasse. Water liquefaction at 280～300 ℃ resulted in formation of more solid residue with high thermal stability.