An innovative two-step noncatalytic esterification technique was proposed to synthesize alkyl esters from free fatty acids simulated in waste cooking oil, as a pretreatment process for biodiesel production, without adding any catalyst under normal conditions of pressure and temperature. The effect of methanol:oil molar ratio, reaction time, mixing rate, and reaction temperature were investigated. The results confirmed that the conversion of the reaction was increased when increasing the methanol molar ratio and decreased in prolonged reaction temperature. High conversion (94.545%) was successfully achieved at optimized conditions of 115:1, 65:1 methanol:oil molar ratio in the first step and second step, respectively, other conditions in both steps were found to be 9 s reaction time, 450 rpm mixing rate, and 62 °C reaction temperature by response surface methodology central composite design. Noncatalytic esterification, which eliminates the complications corresponding with catalyst utilization such as additional cost, time-wasting, and separation requirements, could be considered as a promising pretreatment technique to reduce the high acidity of waste cooking oil to the acceptable limit of 1 mg KOH/g oil or less in two steps, for biodiesel synthesize.

提出了一种创新的两步非催化酯化技术，可以从废食用油中模拟的游离脂肪酸合成烷基酯，作为生物柴油生产的预处理工艺，而无需在正常的压力和温度条件下添加任何催化剂。研究了甲醇：油的摩尔比，反应时间，混合速率和反应温度的影响。结果证实，当增加甲醇摩尔比时，反应的转化率增加，而延长的反应温度则降低。在第一步和第二步分别在115：1、65：1甲醇：油的摩尔比的优化条件下成功实现了高转化率（94.545％），发现两个步骤中的其他条件均为9 s反应时间450 rpm混合速度 反应表面方法采用中心复合设计，反应温度为62°C。非催化酯化技术消除了因使用催化剂而带来的复杂性，例如额外成本，浪费时间和分离要求，可以被认为是一种有前途的预处理技术，可将废食用油的高酸度降低至1 mg KOH /分两步将油克或更少，用于生物柴油合成。