The process for the production of biodiesel can be intensified significantly by employing heterogeneous catalysts that can tolerate free fatty acid in the feedstock. The synthesis of biodiesel was experimentally investigated in a fixed bed reactor using refined sunflower oil (triglyceride) and raw Jatropha oil (triglyceride with free fatty acid). A zinc-based catalyst was used in the form of cylindrical pellets of 6 mm in diameter and 8–10 mm in length. For the raw Jatropha oil, conversions greater than 90% were realized for both triglycerides and free fatty acids (FFAs), typically at 200 °C and a molar ratio of 6 : 1 (methanol : oil) for a residence time of 40 g_cat ml⁻¹ min. The experimental results for the refined oil in the fixed bed reactor (FBR) are explained using an appropriate model that incorporates both simplified kinetics and external mass transfer resistances at liquid–liquid and solid–liquid interfaces. The comparison of FBR results with those of the independent experiments in a spinning basket reactor, in the absence of external mass transfer limitations, shows that the intrinsic reaction is very fast. Hence, in the fixed bed reactor, mass transfer limitations especially at the liquid–liquid interface play an important role under the conditions employed. The rates in the case of refined sunflower oil are significantly lower compared to those of Jatropha oil, due to the presence of FFA, mono- and diglycerides in the latter.

中文翻译：

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使用非均相催化剂研究甘油三酯同时酯化和酯交换的传质限制

通过使用可耐受原料中游离脂肪酸的非均相催化剂，可以显着增强生物柴油的生产过程。在固定床反应器中使用精制的葵花籽油（甘油三酸酯）和粗麻风树油（带有游离脂肪酸的甘油三酸酯）对生物柴油的合成进行了实验研究。锌基催化剂以直径为6毫米，长度为8至10毫米的圆柱形小球形式使用。对于粗麻风树油来说，甘油三酸酯和游离脂肪酸（FFA）的转化率通常都在200°C，摩尔比为6：1（甲醇：油），停留时间为40 g _cat时，转化率均达到90％以上。毫升^-1分钟 使用适当的模型解释了固定床反应器（FBR）中精炼油的实验结果，该模型结合了简化的动力学和液-液和固-液界面的外部传质阻力。在没有外部传质限制的情况下，将FBR结果与在纺丝篮式反应器中的独立实验的结果进行比较，表明内在反应非常快。因此，在固定床反应器中，传质限制，特别是在液-液界面处，在所采用的条件下起着重要的作用。精制葵花籽油的使用率比麻风树油低得多，这是因为后者中存在FFA，甘油一酸酯和甘油二酯。