【作者】 彭军；

【导师】 郑小明； 陈平；

【作者基本信息】 浙江大学 ， 物理化学， 2009， 博士

【摘要】 由生物质通过热裂解或液化的方法可以制取生物油。生物油的使用不会增加CO₂的净含量,被认为是一种清洁的可再生能源,具有替代化石燃料的潜力。生物油的成分复杂,含有多种化合物,包括酸类、酚类、醛类、酮类、酯类以及糖类等物质。生物油容易缩合而导致不稳定,它较强的酸性、高含水量、高含氧量、高黏度以及低热值等性质大大阻碍了其作为燃料的广泛使用。因此,生物油在使用前必须经过提质处理,以增强其品质。传统的生物油提质的目标是尽量脱除其组分中的氧以提高其热值和稳定性,这样会带来大量的氢耗和能耗。本论文提出一个新的思路:通过多个提质反应过程的归并、耦合,将生物油中多种复杂而不稳定的分子尽量一步转化为稳定的含氧或不含氧分子,含氧化合物形式的存在不仅可以提高生物油的有效元素利用率,降低提质反应的能耗,而且含氧燃料可改善油料的燃烧性能、减少发动机尾气污染。论文首次提出并设计了在超临界醇类介质环境下生物油提质的过程,通过这个过程成功地一步完成了多个反应过程的归并、耦合,使生物油实现了非常有效的提质。论文建立了生物油的分析方法,通过气相色谱.质谱联用（GC-MS）对生物油的主要组分及其提质前后的变化实现了有效的监测,为实验的进行提供了基础。通过分析发现,生物油原油的含水量约占28.0%,含氧量约占51.2%,热值为16.5MJ/kg左右,不到化石燃料的一半。GC-MS分析表明,生物油中的有机组分包含酸类（33.17%）、酚类（16.06%）、酯类（6.85%）、酮类（17.82%）、醛类（4.45%）以及糖类（15.38%）等物质,是一种复杂的多元含氧有机物的混合物。热重分析表明,在氧气存在的条件下,生物油在430℃左右会迅速完全燃烧。论文提出适用于生物油超临界提质反应的介质的临界温度应介于200℃～300℃之间,其临界压力应不大于10MPa。同时要求,超临界反应介质不能对环境产生严重不利影响,能够燃烧,具备用作燃料的特点,最好能和生物油具有很好的混合调和性能。论文对正己烷、乙酸乙酯、丙酮、异丙醇、甲醇以及乙醇等6种超临界介质进行了生物油提质的探索。结果发现,超临界醇类是生物油提质的有效介质。酯类在超临界条件下会大量水解生成酸而不适合。烷烃则由于其非极性不易与生物油互溶而不适合作为生物油提质的超临界介质。论文对固体酸催化下的超临界乙醇中生物油的提质进行了研究。Al₂（SiO₃）₃表现出最好的提质效果。在260℃、醇油比为10∶1的条件下,提质后酸类物质总的相对含量由提质前的33.17%降低到1.76%,酚类物质总的相对含量由提质前的16.06%降低到3.05%,酮类物质由提质前的17.82%降低到1.95%。糖类物质和醛类物质分别由提质前的15.38%和4.45%降低到零,即完全消失。酯类物质总的相对含量由提质前的6.85%升高到69.57%,提质后生物油的酸度、粘度明显降低、热值有所增加。这是一个令人鼓舞的新结果,有很好的应用前景。论文还对其反应条件进行优化并对提质反应机理作了初步的探讨。以HZSM-5为催化剂的生物油超临界提质产物,通过减压蒸馏实验发现,提质后的生物油的蒸馏残余物的质量百分含量低于未经提质的生物油原油的蒸馏残余物的质量百分含量。随着所用催化剂HZSM-5的Si/Al下降（酸性则随着上升）,提质后的生物油的蒸馏残余物的质量百分含量降低,气相产物中的CO₂大量增加,表明酸性大的HZSM-5有利于裂解反应的发生,从而有利于降低生物油中的重组分含量。论文对超临界甲醇生物质提质进行了研究,证明甲醇也是很有效的生物油提质的介质。更有趣的是,由于甲醇的酸性和疏水性比较强,在没有催化剂存在时,对生物油的提质也有很好的效果。这个结果有很高的实用价值,可以避免使用固体催化剂的诸多麻烦如催化剂的分离、积碳、稳定性等等,对生物油超临界提质提供了一个不错的选择。对生物油进行了分级加氢提质的初步探索。利用减压蒸馏的方法将生物油原油分为轻质生物油和重质生物油,利用Pd/HZSM-5,Pt/HZSM-5,Rh/Al₂（SiO₃）₃,Ni/HZSM-5,Co/Al₂（SiO₃）₃等贵金属和过渡金属催化剂,分别对轻质生物油和重质生物油进行了催化加氢提质反应。结果表明,生物油的分级提质提高了提质反应的针对性,能有效的促进重质生物油的提质。以糠醛和香草醛为分子探针,进行生物油模型化合物的催化加氢提质反应,分析了产物分布,并对其反应机理进行了初步探讨。结果表明,酸性载体上负载的贵金属催化剂除了有加氢作用外,还有裂解及重整等作用。更多还原

【Abstract】 Bio-oil,a liquid product from renewable biomass via liquefaction or pyrolysis,by the virtue of its environmentally friendly potential such as CO₂ neutrality,is regarded as a promising renewable energy source and received more and more attention.The crude bio-oil is a complicated oxygenated mixture which generally contains a wide variety of acids,phenols. esters,ketones,aldehydes and sugars,and as a result,crude bio-oil exhibits some undesired properties such as acidity,high viscosity,and thermal instability.On the other hand,high water and oxygen content in crude bio-oil leads to its low heating value compared with that of fossil fuels.Therefore bio-oil needs to be upgraded to improve its quality for its practical application. At present,the main aim of bio-oil upgrading processes carried out by most investigators is to obtain hydrogecarbons by removing the O-compounds in bio-oil in which catalytic hydrodeoxygenation process is mostly used.The main disadvantage of catalytic hydrodeoxygenation process is the high consumption of hydrogen and energy due to the high temperature and hydrogen pressure required in this method.The aim of this work is to produce oxygenated fuel through bio-oil upgrading using an environmentally friendly method with low energy consumption.One-pot reaction in supercritical fluids,an innovative route for bio-oil upgrading was developed in this work.The instable compounds in bio-oil are converted into stable O-compounds or other compounds through one-pot reaction in which many reactions are coupled and merged.The process was carried out under mild conditions and in which,the crude bio-oil was converted into oxygenated fuel.This method can enhance the use efficiency of elements in bio-oil.The basic properties and compositions of bio-oil from fast pyrolysis of rice husk were analyzed using GC-MS.TG.vacuum distillation and other conventional methods.Crude bio-oil has high water content（28.0%）,high oxygen content（51.2%） and low heating value（16.5 MJ/kg）.The organic components of crude bio-oils include acids（33.17%）.phenols（16.06%）. esters（6.85%）,ketones（17.82%）.aldehydes（4.45%） and sugars（15.38%）.TG analvsis showed that completed combustion of bio-oil in oxygen occurred at 430℃. Ethanol and methanol were selected as supercritical reaction media in the supercritical upgrading processes due to their mild critical conditions and advantageous effect on the upgrading reactions.On the other hand,ethanol is mainly produced from biomass while methanol is mainly produced from fossil fuels and these two alcohols all can be used as vehicle fuels.Therefore the investigation of upgrading of bio-oil in supercritical ethanol and methanol is an innovative work for combined utility of alcohol fuels and bio-oil.The crude bio-oil was upgraded in supercritical ethanol using Al₂（SiO₃）₃ as catalyst at 260℃with 10:1 ethanol/oil ratio.The results showed that supercritical upgrading process performed effectively and the components of upgraded bio-oil were optimized greatly.Acidic aluminum silicate facilitates esterification in supercritical ethanol to convert most acids contained in crude bio-oil into various kinds of esters.The amount of esters in upgraded bio-oil increased from 6.85%to 69.57%and the amount of acids decreased from 33.17%to 1.76%.The amount of phenols decreased from 16.06%to 3.05%.Aldehydes such as furfural and vanillin which are typically present in crude bio-oil were removed during supercritical upgrading process and not detected in upgraded bio-oil.Sugars,which are largely（15.38%） contained in crude bio-oil were converted completedly in supercritical upgrading process.The pH value and heating value of upgraded bio-oil increased compared with that of crude bio-oil.The viscosity of upgraded bio-oil decreased.The changes of these properties showed that the quality of upgraded bio-oil was improved.It proved that supercritical upgrading process is so effective and promising that can be developed into an industrial method.The crude bio-oil was upgraded in supercritical ethanol using HZSM-5（Si/Al=22,100,300） as catalyst.The amount of distillation residue of upgraded bio-oil decreased compared to that of crude bio-oil.With the increasement of acidity of HZSM-5（decrease of Si/Al ratio）,the amount of distillation residue of upgraded bio-oil decreased and at the same time,the amounts of ethylene and CO₂ in gas phase products increased.These results showed that stronger acidic HZSM-5（low Si/Al ratio） can facilitate cracking of heavy,components of bio-oil more effectively in supercritical upgrading process.Methanol is another effective reactive medium for bio-oil upgrading.It is interesting to found that bio-oil upgrading process works effectively in supercritical methanol even without catalyst. Hydrogenation of light and heavy bio-oil（defined as distillate and residue of crude bio-oil through vacuum distillation,respectively） was investigated.It was found that separation of heavy bio-oil from crude bio-oil can facilitate hydrogenation process.Furfural and vanillin ware used as molecular probes to examine the mechanism of hydrogenation process and it showed that cracking,reforming and hydrogenolysis were involved in hydrogenation process.更多还原