Biodiesel synthesis from bio-heavy oil through thermally induced transesterification
Biodiesel synthesis from bio-heavy oil through thermally induced transesterification
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DOI：
10.1016/j.jclepro.2021.126347
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发表时间：
2021-02-17
影响因子：
11.1
通讯作者：
Kwon, Eilhann E.
中科院分区：
文献类型：
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作者：
Jung, Sungyup;Kim, Minyoung;Kwon, Eilhann E.
大量未反应脂肪酸和单/二/甘油三酯的混合物，即生物重油，作为生物柴油工业的废物产生。考虑到脂质（即甘油三酯）占生物柴油总生产成本的80%，将生物重油转化为生物柴油可能是提高经济/环境效益的可行途径。尽管如此，游离脂肪酸和杂质的高含量限制了生物重油转化为生物柴油的实际增值，因为传统的酸/碱催化酯交换受到杂质的影响。为了克服这一技术挑战，本研究提出了一种通过热诱导酯交换将生物重油转化为生物柴油的直接增值平台。在生物柴油生产之前，对生物重油的酸值（105 mg KOH g（-1）生物重油）、元素组成和热稳定性等特性进行了表征。用H2SO4催化的酸催化酯交换反应在60℃下反应24小时后，生物柴油的产率为31.1%。然而，在没有催化剂的多孔介质（SiO2）下，在400℃下反应1分钟后，热诱导酯交换反应的生物柴油产率为59.3%。多孔SiO2（孔径为6 nm）为脂质和甲醇提供了密闭的空间，使其在高温下能够快速进行酯交换反应。热诱导酯交换反应产率在360℃时与反应温度成正比，但在400℃时由于不饱和烃化学键断裂，产率下降。热诱导（非催化）酯交换反应生成C6-22脂肪酸甲酯（FAMEs），无论反应条件如何，各FAMEs的质量分数都是恒定的
A huge amount of a mixture of unreacted fatty acids and mono/di/triglycerides, namely bio-heavy oil, is generated as a waste from biodiesel industry. Considering that the lipid (i.e., triglycerides) accounts for 80% of the total biodiesel production cost, valorization of bio-heavy oil into biodiesel can be a viable route for enhancing the economic/environmental benefits. Nonetheless, the high contents of free fatty acids and impurities have restricted practical valorization of bio-heavy oil into biodiesel because conventional acid/base catalyzed transesterification suffers from the presence of the impurities. To overcome the technical challenge, this study suggested a direct valorization platform for the conversion of bio-heavy oil into biodiesel via thermally induced transesterification. Prior to biodiesel production, the properties of bio-heavy oil, such as acid value (105 mg KOH g(-1) bio-heavy oil), its elemental compositions and thermal stability were characterized. Acid-catalyzed transesterification with a H2SO4 catalyst showed the 31.1 wt % of biodiesel yield after 24 h of reaction at 60 degrees C. However, thermally induced transesterification exhibited 59.3 wt% of biodiesel yield after 1 min of reaction at 400 degrees C using a porous medium (SiO2) with no presence of a catalyst. The porous SiO2 (pore size: 6 nm) provided confined spaces for lipids and methanol, allowing the rapid transesterification reactions between them at high temperature. The biodiesel yield from thermally induced transesterification was proportionate to reaction temperature by 360 degrees C, but it decreased at > 400 degrees C due to the chemical bond scissions of unsaturated hydrocarbons. C6-22 fatty acid methyl esters (FAMEs) were produced from thermally induced (non-catalytic) transesterifications, and weight fractions of each FAMEs were constant, regardless of the reaction conditions at