Cloud point and crystallization in fatty acid ethyl ester biodiesel mixtures with and without additives

Biodiesels, composed of saturated fatty acid alkyl esters (FAAE), have relatively high cloud points (CP), which limit their commercial application. However, fatty acid ethyl esters (FAEE) have potentially advantageous properties, including those related to cold flow, compared to their methyl analogs. This work systematically evaluates FAEE cloud point and crystallization data to aid in the development of FAEE biodiesel blends with practical cold flow properties. Neat FAEE CP increases with alkyl-chain length and decreases with greater degree of unsaturation. Mixtures of saturated/saturated FAEE show partial cocrystallization, which impact the mixture’s CP. The effects of cold-flow improving additives dimethyl azelate (DMAz) and triacetin on fatty acid methyl esters (FAME) and FAEE are also analyzed. Additives lowered the overall CP, however the degree of depression for each additive varied indicating different crystallization mechanisms. Thermodynamic ideal solution modeling predicts binary FAEE CP with and without additives within 2% of experimental values.

生物柴油由饱和脂肪酸烷基酯（FAAE）组成，其浊点（CP）相对较高，这限制了它们的商业应用。然而，与甲基类似物相比，脂肪酸乙酯（FAEE）具有潜在的优势特性，包括与冷流相关的特性。这项工作系统地评估了脂肪酸乙酯的浊点和结晶数据，以帮助开发具有实用冷流特性的脂肪酸乙酯生物柴油混合物。纯脂肪酸乙酯的浊点随烷基链长度增加而升高，随不饱和度增加而降低。饱和/饱和脂肪酸乙酯的混合物显示出部分共结晶，这影响了混合物的浊点。还分析了冷流改进添加剂壬二酸二甲酯（DMAz）和三乙酸甘油酯对脂肪酸甲酯（FAME）和脂肪酸乙酯的影响。添加剂降低了总体浊点，但每种添加剂的降低程度不同，表明结晶机制不同。热力学理想溶液模型预测含添加剂和不含添加剂的二元脂肪酸乙酯浊点与实验值的偏差在2%以内。