【作者】 熊万明；

【导师】 郭庆祥；

【作者基本信息】 中国科学技术大学 ， 可再生洁净能源， 2010， 博士

【摘要】 能源与环境是关系国计民生的两个重大问题。作为唯一可直接转化为液体燃料的资源,生物质具有可再生和洁净等优点,引起了广大研究工作者的兴趣。通过高温快速热裂解生物质所得的生物油,不仅有望替代传统的化石燃料,还可以提供大量的化学品原材料,因而具有重要的研究价值和战略意义。但是现阶段的生物油品质还不够理想,极大地限制了其应用范围和产业化进程。因此,对生物油进行一定的精制加工处理是十分必要的。本研究以将生物质转化成高品位液体燃料为目的,在认识生物油的物理特性和化学组成等特点的基础上,围绕生物油的分离与精制的主题,致力研发一系列绿色环保的催化剂和工艺,对生物油开展了一系列基础性而又有针对性的分离与精制的研究。针对生物油含有裂解木质素和低聚糖等大分子物质,利用超临界流体萃取技术将其高效地除去；针对生物油中的强腐蚀性,采用催化酯化可以将生物油中的有机酸转变成酯类,从而改善油品质量；针对生物油中含有许多不饱和性物质,采用催化氢化的方式使其饱和,提高生物油的稳定性和燃烧性能。通过上述研究,实现了对生物油从单一提质发展到全方位提质加工的转变。论文第一章首先阐述了生物质转化与利用技术的现状；介绍了现阶段生物油的性质与成分组成；综合分析了当前生物油分离与精制的发展状况与趋势,并就其中存在的优点和缺点进行了简要的讨论；最后提出了本课题的研究内容和研究目标,并简单介绍了实验方法以及论文安排等。第二章主要介绍通过引进超临界二氧化碳萃取技术,实现了生物油轻质组分与低聚物、多羟基化合物的分离实验。在T=41℃,P=16 MPa的条件下,经萃取5h,可得60.4wt%的产物。该萃取油品的物化特性得到了很好的改善：黏度从1303 mm2／s下降到2.67 mm2／s；密度由1.20 g／mL降低到0.98g／mL,萃取油的稳定性明显优于萃取前的生物油。因此,超临界二氧化碳萃取这种绿色环保的技术实现了预期的生物油提质效果,同时不给环境带来负担。第三章主要讨论了纳米固体超强酸S042-／Zr02和离子交换树脂等固体催化剂在生物油催化酯化提质研究的中的应用。考察了催化剂在温和条件下催化酯化的活性和循环使用的情况。此外,对催化酯化方法处理生物油的品质改良程度以及工艺进行了简要的评估。在60～110℃条件下反应2-3h,酯化反应就可以完成,没有发生聚合、结焦的现象；酯化后的萃取油中的乙酸的含量明显降低,生物油的稳定性、热值等方面均有提升。强酸性离子交换树脂在效率方面要稍微优于纳米型固体酸,不仅分离更为简单,且无需处理直接循环利用。第四章介绍均相催化酯化提质生物油的研究。在模型反应的基础上,筛选出了催化活性强的双阳离子型离子液体催化剂；考察了催化剂的生物油提质的效果。结果显示酯化反应可以在常温常压条件下,且在较短时间3-6h内完成。酯化后的生物油自动发生分层,其中上层为提质酯层,产率接近48wt%；该层的提质油的物化特性较之酯化前的生物油得到极大的提升：水分由29.8wt%降低到8.2wt%；热值由17.3 MJ/kg升高到24.6 MJ/kg;黏度由13.03 mm2／s下降到4.90mm2／s；更为重要的是油样的pH值由2.9上升到5.1,很大程度上解决了生物油腐蚀性问题。另外,这种均相催化酯化反应不仅实现了高效地催化转化生物油中的有机酸,而且避免了固体超强酸所带来的酸性流失问题,循环使用性强,为生物油的酯化提供了一条切实可行的路线。第五章介绍了甲酸原位还原生物油的方法。首先比较了原位还原与直接氢化还原的效果,然后分析了各种催化剂在生物油原位还原反应中的催化效率；最后通过GC-MS检测结果,详细分析了原位还原中发生的化学反应,以及这些反应对生物油品质的影响。原位还原有效地避免了在直接还原方式中的结焦,传质传热等问题,还原效率更高,工艺设备得到了简化。加工后的生物油品质得到了极大的改善：热值从17MJ/kg左右升高到22MJ/kg,含氧量降低5-10wt%,pH值也从3.0升高到4.2左右,黏度由5.31mm2／s降低到4.0mm2／s左右,实现了全方位的提质生物油。成分分析表明生物油中的有机酸被有效地转化成酯类；生物油中碳碳和碳氧双键的化合物有效地被还原,但稳定的芳环结构环没有被还原；部分低聚物发生了氢化裂解反应；此外,没有分解完全的甲酸也与甲醇形成了甲酸甲酯,从而不影响产物的燃料性质。通过原位还原处理,一步就解决了生物油的热稳定性和腐蚀性问题,实现了全方位提质生物油的效果。综上所述,通过上述各种方法提质后的油品质量得到了很大的改善,催化剂和工艺设备绿色环保,且具有一定的产业化潜质,为生物油精制加工提供了重要技术支撑。更多还原

【Abstract】 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.更多还原