This study explored the direct esterification of palmitic acid and ethanol using a deep eutectic solvent (DES) as catalyst to produce biodiesel. Three novel deep eutectic solvents (DTAC-PTSA, DTAC-2PTSA, DTAC-3PTSA) were successfully prepared by mixing dodecyl trimethyl ammonium chloride (DTAC) and p-toluenesulfonic acid monohydrate (PTSA) in a molar ratio of 1: z (z=1, 2, 3). After testing, DTAC-3PTSA was found to have the best catalytic performance among the three types of DESs and was therefore selected as the catalyst for subsequent experiments. The effects of agitation speed, ethanol to palmitic acid molar ratio (α), temperature and catalyst dosage were studied by investigating the change of palmitic acid conversion rate with time under different conditions, respectively. Then, the pseudo-homogeneous (PH) model was utilized to describe the kinetic behavior of this reaction between 328.15–348.15 K and it was found to work well for the experimental data obtained. Moreover, the catalytic performance of DTAC-3PTSA was detected to have no significant change in the cycle test. Therefore, DTAC-3PTSA can be considered as a substitute for traditional catalysts to produce biodiesel and the kinetic data obtained here can be used for further up-scaling study.

中文翻译：

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基于十二烷基三甲基氯化铵的低共熔溶剂催化棕榈酸与乙醇反应的动力学研究

本研究探索了使用低共熔溶剂 (DES) 作为催化剂直接酯化棕榈酸和乙醇以生产生物柴油。通过将十二烷基三甲基氯化铵 (DTAC) 和对甲苯磺酸一水合物 (PTSA) 以 1: z (z= 1、2、3）。经过测试，发现DTAC-3PTSA在三种DESs中催化性能最好，因此被选为后续实验的催化剂。通过考察不同条件下棕榈酸转化率随时间的变化，分别研究了搅拌速度、乙醇与棕榈酸摩尔比(α)、温度和催化剂用量的影响。然后，拟均相 (PH) 模型用于描述该反应在 328.15-348.15 K 之间的动力学行为，并且发现它对于获得的实验数据很有效。此外，在循环测试中检测到DTAC-3PTSA的催化性能没有显着变化。因此，DTAC-3PTSA 可以被视为传统催化剂的替代品来生产生物柴油，这里获得的动力学数据可用于进一步的放大研究。