Studies On The Separation And Upgrading Of Bio-Oil

Energy and environment are important for every country, especially for our country. As the only one feed resource that can convert directly to liquid fuel, biomass has the advantages of aboudance, renewable and clean, and has caused the extensive concern in recent years. Through flash pyrolysis of biomass, the liquid product, known as bio-oil, not only is expected to replace traditional fossil fuels, but also to provide a lot of chemicals, raw materials. However, the quality of bio-oil is still not ideal, which limits its application and industrialization process. Therefore, an upgrading approach is necessary for the present bio-oil.According to the physical properties and chemical composition of bio-oil, a series of bio-oil separation and upgrading processes, as well environmental catalysts were proposed in our studies. The supercritical fluid extraction was employed to remove the oligomers; catalytic esterification was employed to convert the organic acids into the esters, so as to lower the high corrosion of bio-oil; while with catalytic hydrogenation process, most of the unsaturated component can be reduced so as to refine bio-oil. With these treatments, the change on the bio-oil quality from a single modification developing to all aspects upgrading was achieved.In the first Chapter, the state of the biomass conversion and utilization technology was described at benign, and the properties and chemical composition of the present bio-oil were introduced; then comprehensive analysis current evelopment status and trends in bio-oil separation and upgrading, and simple discuss the Pros and Cons of the treatments; at last, this research projects and methods, as well as arrangements of this paper, were briefly described.In the ChapterⅡ, studies focuses on the bio-oil separation through supercritical carbon dioxide extraction technology. Under the condition of T=41℃, P=16 MPa, and the extraction time of 5h, the extraction yield was 60.4 wt%. The physical and chemical properties of extracted oil have been well improved. The viscosity lowered from 13.03 mm2/s to 2.67 mm2/s; the density reduced from 1.20 g/mL to 0.98g/mL, and the stability of the extracted oil is superior to the bio-oil. Therefore, the supercritical carbon dioxide extraction process achieves the desired upgrading effect, at the same time, which avoids environment burden.In ChapterⅢ, the experiments research on the nanometer solid superacid SO42-/ZrO2 and ion-exchange resins applying in bio-oil catalytic esterification were described. At 60～110℃, the esterification reaction can be completed in 2-3h, and the polymerization, coking phenomenon did not occur during the reaction. The acetic acid content was lowered significantly, and the conversion rate of it is about 90%; consequently, the bio-oil stability, higher heating value, etc. have been improved. Moreover, the strong acidic ion-exchange resins are better than the solid acid, and the separation convenient is simpler.Homogeneous catalytic esterification of bio-oil had been examined in Chapter IV. With the ionic liquid catalyst, the esterification reaction can be carried out smoothly under the conditions of normal temperature and pressure, and in a relatively short time (3-6h). When the reaction was completed, the organic acids converted completely into the esters, and the reaction system turned into two layers (esters mixture and water). The properties of upgraded oil were improved significantly. The higher heating value approached to 24.6 MJ/kg, and the pH value rose from 2.9 to 5.1, as well as moisture decreased from 29.8 to 8.2 wt%. In addition, this ionic liquid catalyst can avoid the acidity loss of solid superacid, and its recycling is convenient.In the V Chapter, the effect of an in situ reduction process on the bio-oil upgrading was described. The treatments were preformed at 170～200℃for 5～10 h, in which the formic acid was decomposed into hydrogen and carbon dioxide, and then hydrogen reduces the bio-oil while compressible CO2 dissolves in methanol to form a CO2-CH3OH expanded liquid. With the effect of in situ reduction, the recovery yield of the liquid product was 80-90wt% and there was no obvious coke formation. The unsaturated components in bio-oil were reduced successfully, while the organic acids were converted into esters via reaction with methanol, and the oxygen content was lowered by ca.5～10 wt%. The properties of hydrogenated bio-oil were improved:the pH value increased from 3.0 to ca.4.2; the higher heating value approached to 20 MJ/kg, and the viscosity decreased from 5.31 mm2/s to ca.4.0 mm2/s.In summary, the quality of bio-oils has been improved to a certain extent; the catalysts, as well upgrading processes was environmental sustainability, and which is good for bio-oil research and development.