The crude oil extracted from milk thistle seeds was employed as a precursor for creating biodiesel (BD) via the cosolvent esterification–transesterification process. The high acid value of the extracted oil (11.90 mg KOH/g) encouraged its pre-esterification in the occurrence of hexane as a cosolvent. The cosolvent esterification of oil diminished its acidity index to below 2.0 mg KOH/g using 1.5:1 hexane:methanol volume ratio, 50°C, 60-min reaction time, 6:1 methanol:oil molar ratio, and 0.75 wt.% HCl. Alcoholysis reaction of the esterified oil with methanol and a blend of methanol:ethanol to synthesize, respectively, methylic BD and methylic/ethylic BD was accomplished in the presence of hexane as a cosolvent as well. Under the ideal reaction conditions, methylic BD yield and methylic/ethylic BD yield were 96.23% and 95.63%, respectively. The Fourier-transform infrared (FTIR) and ¹H nuclear magnetic resonance (NMR) spectra affirmed the lipid transformation from milk thistle seeds into BD. The attained samples of BD exhibited properties conforming to those specified by ASTM D6751. Also, the cosolvent methanolysis kinetic obeyed the pseudo-first-order with 35.94 KJ/mol activation energy and 6.32-s frequency factor.

中文翻译：

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通过共溶剂酯化-酯交换工艺从奶蓟籽油作为非食用油生产生物柴油

从奶蓟种子中提取的原油被用作通过共溶剂酯化-酯交换过程制造生物柴油 (BD) 的前体。提取油的高酸值 (11.90 mg KOH/g) 促进了其在己烷作为共溶剂时的预酯化。使用 1.5:1 己烷:甲醇体积比、50°C、60 分钟反应时间、6:1 甲醇:油摩尔比和 0.75 wt.%，油的共溶剂酯化将其酸度指数降低至低于 2.0 mg KOH/g盐酸。酯化油与甲醇和甲醇：乙醇的混合物的醇解反应分别合成甲基BD和甲基/乙基BD是在己烷作为共溶剂存在下完成的。在理想的反应条件下，甲基BD产率和甲基/乙基BD产率分别为96.23%和95.63%。¹ H 核磁共振 (NMR) 光谱证实了从奶蓟种子到 BD 的脂质转化。得到的 BD 样品表现出符合 ASTM D6751 规定的特性。此外，共溶剂甲醇分解动力学遵循伪一级，活化能为 35.94 KJ/mol，频率因子为 6.32-s。