【作者】 李俊；

【导师】 曾阔；

【作者基本信息】 华中科技大学 ， 动力工程， 2021， 硕士

【摘要】 藻类生物质作为一种新型且清洁的可替代能源具有非常可观的应用前景。热解有助于实现藻类生物质向生物燃料的高效转化。然而,藻类生物质中较高的氮元素含量会造成其热解生物油中存在大量含氮化合物。同时,藻类热解生物油还含有大量性质不稳定、组分复杂的重质油组分。这两个缺陷极大地降低了生物油的品质,迫使生物油在生产、应用以及后续升级中面临严峻的环境问题和经济效益问题,很大程度地限制了藻类热解生物油的推广应用。本文重点探究了藻类热解生物油的组成特性以及热解过程中含氮化合物的形成转化路径,有利于指导实现藻类热解生物油的高效、高质利用。采用固定床反应器对三种不同藻类生物质（浒苔藻（EP）、螺旋藻（SP）和拟微绿球藻（NS））在300℃–700℃下进行了加热速率为10–25℃/s的热解实验。通过气相色谱-质谱（GC-MS）、傅立叶变换离子回旋共振质谱（FT-ICR-MS）配备用户自定义的Matlab程序对热解制得的生物油及其重质油组分进行了研究。在此基础上,先是探究了GC-MS和FT-ICR-MS在藻类生物油组分检测效果上的适用性和匹配性,然后讨论了藻类组分差异和热解温度对生物油产物组成和含氮化合物的影响,最终获得了生物油重质油组分中氮元素迁徙转化的可能路径。正离子电喷雾（ESI）对生物油中含氮化合物有更好的电离效果,甲醇作为藻类热解生物油溶剂可同时匹配GC-MS和FT-ICR-MS设备。在生物油的研究过程中,GC-MS检测结果中CHO组分含量要比FT-ICR-MS高很多,而含氮组分（CHN+CHON）含量要低很多,可能是因为生物油中CHO组分的分子量普遍偏小,而含氮数多的化合物往往挥发性差。此外,GC-MS只分析出极少量含硫化合物,而FT-ICR-MS分析结果中,含硫化合物主要是S₁和S₁O_1-2(S₁O_1-5)组分,含量可超过20%。两种设备在化合物分子质量检测范围和理化性质上有所互补,但检测结果难以有效统一也是亟需要解决的问题。FT-ICR-MS结果显示,生物油中存在大量重质油（分子质量≥200 Da）组分。随着温度升高,这些重质组分会逐渐向轻质组分转化。SP和NS重质油只在700℃下含有少量稠环芳烃,含量分别为2.43%和1.62%,糖类物质（0.25%–5.01%）也仅在300℃–600℃下出现在EP重质油中。在300℃–700℃时,SP和NS重质油主要以N_1-3组分为主,其含量超过60%,主要是一些酰胺类、腈类和含氮杂环类（吲哚、喹啉等）等化合物,而EP重质油主要以N₀和N₄类化合物为主,其含量可达50%–68%。重质油中含氮化合物在高温下会发生强烈的美拉德反应和脱氧反应,从而芳香性变得更强、含氧更少。总体而言,利用藻类生物质热解制取高品质生物油和高附加值化合品时,既需要关注生物油产率,还需要关注重质油组分和含氮组分特性。更多还原

【Abstract】 Algae,as a new and clean alternative energy,has a promising application prospect.Pyrolysis is helpful to realize the efficient conversion of algae into biofuels.However,the high nitrogen content in algae results in a large quantity of nitrogen-containing compounds in its pyrolysis bio-oil,which also contains numerous heavy-oil components with complex and unstable properties.These two defects greatly reduce the quality of bio-oil,leading to the severe environmental and economic problems in the production,application and subsequent upgrading of bio-oil,which seriously restrict the promotion and application of algae pyrolysis bio-oils.This work focuses on exploring the composition characteristics of algae pyrolysis bio-oil and the formation and evolution path of nitrogen-containing compounds in the pyrolysis process,it is conducive realizing the efficient and valuable utilization of algae pyrolysis bio-oil.Three different algae,Nannochloropsis sp.（NS）,Spirulina platensis（SP）and Enteromorpha prolifera（EP）,were pyrolyzed at a heating rate of 10–25℃/s at 300℃–700℃ in a fixed-bed reactor.The pyrolysis bio-oil and its heavy-oil components were characterized by a gas chromatography-mass spectrometry（GC-MS）,a Fourier transform ion cyclotron resonance mass spectrometry（FT-ICR-MS）and a user-defined Matlab program.On this basis,the applicability and compatibility of GC-MS and FT-ICR-MS were investigated in the study of algal bio-oil components.Then,the effects of algae with different components and pyrolysis temperature on the bio-oil composition and nitrogen-containing compounds were discussed.Finally,the possible evolution path of nitrogen in the heavy-oil was obtained.The positive electrospray ionization had a better ionization effect on nitrogen-containing compounds in bio-oil,and methanol,as a solvent for algae pyrolysis bio-oil,matched both GC-MS and FT-ICR-MS devices.In terms of bio-oil study,the content of CHO component in GC-MS results was much higher than that of FT-ICR-MS,while the content of nitrogen-containing component（CHN+CHON）was much lower.It may be because the molecular weight of CHO components in bio-oil is relatively small,and the compounds with more nitrogen number tends to be less-volatile.In addition,GC-MS only analyzed a very small amount of sulfur compounds,while FT-ICR-MS results showed that the sulfur compounds content could exceed 20%,mainly S₁ and S₁O_1-2(S₁O_1-5)components.The two devices were complementary in the molecular weight and physicochemical properties of the bio-oil compounds,but these two results are difficult to be unified,which is an urgent problem to be solved.FT-ICR-MS results showed that there were a lot of heavy-oil components（molecular weight≥200 Da）in the bio-oil.As the temperature rises,these heavy-oil components gradually transformed to lighter components.SP and NS heavy-oils only contained small amounts of condensed aromatics（2.43%and 1.62%,respectively）at 700℃,while carbohydrates（0.25%–5.01%）only appeared in EP heavy-oils at 300℃–600℃.At 300℃–700℃,SP and NS heavy-oils were mainly composed of N_1-3 components with the content of more than 60%,mainly amides,nitriles and nitrogen-containing heterocyclic compounds（indole,quinoline,etc.）.EP heavy-oils mainly contained N₀ and N₄ compounds,the content of which can be up to 50%–68%.Nitrogen-containing compounds in heavy-oils underwent strong Maillard reaction and deoxygenation reactions at high temperatures,thereby becoming more aromatic and containing less oxygen.In general,when algae pyrolysis is used to produce high quality bio-oil and high value-added compounds,attention should be paid not only to the yield,but also to the characteristics of heavy-oil components and nitrogen-containing components.更多还原