In this study, oleic acid was used as a model compound to discuss the mechanism of thermal conversion of unsaturated fatty acids to hydrocarbons, so as to promote the goal of obtaining renewable chemicals and fuels from unsaturated fatty acids. In-situ detection techniques such as TG-FTIR and Py-GC/MS combined with density functional theory were applied to study the reaction mechanism of oleic acid molecules in the conditions of slow pyrolysis and fast pyrolysis. As the temperature rises, the hydrogen bond is broken, and the vibration peak of oleic acid shows obvious dehydrogenation under slow pyrolysis, and the same situation exists under fast pyrolysis. As the temperature increases, the pyrolysis process of oleic acid molecules changed from the dominant role of bimolecular mutual catalysis to that of free radical reaction. The results of Py-GC/MS showed that methyl, ethyl, and hydrogen radicals are the main active substances under the conditions of high temperature and fast pyrolysis of unsaturated fatty acid. This work demonstrates the feasibility of producing renewable hydrocarbons by pyrolysis of unsaturated fatty acids and proposed influenced factors to control product distribution.

中文翻译：

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不饱和脂肪酸热解机理的研究：结合密度泛函理论和实验研究

本研究以油酸为模型化合物，探讨了不饱和脂肪酸热转化为碳氢化合物的机理，以促进从不饱和脂肪酸中获得可再生化学品和燃料的目标。应用TG-FTIR、Py-GC/MS等原位检测技术结合密度泛函理论，研究了慢热解和快速热解条件下油酸分子的反应机理。随着温度的升高，氢键断裂，油酸的振动峰在慢速热解下表现出明显的脱氢现象，在快速热解下也存在同样的情况。随着温度的升高，油酸分子的热解过程从双分子相互催化的主导作用转变为自由基反应的主导作用。Py-GC/MS结果表明，甲基、乙基和氢自由基是不饱和脂肪酸在高温和快速热解条件下的主要活性物质。这项工作证明了通过不饱和脂肪酸的热解生产可再生碳氢化合物的可行性，并提出了控制产品分布的影响因素。