超声波辅助煎炸废油酯交换制备生物柴油

摘要

With bleached waste frying oil (acid value 4. 20 mgKOH/g, moisture and volatile matter con-tent 0. 072%, saponification value 197. 24 mgKOH/g, average molar mass 871. 82 g/mol) as raw mate-rial and KOH as catalyst, biodiesel was produced by ultrasound-assisted transesterification and analyzed by gas chromatography. Based on previous research on the reaction conditions ( molar ratio of methanol to oil 6∶1 and catalyst dosage 1% ( based on the mass of bleached waste frying oil ) ) , the reinforcement effect of ultrasound on transesterification was studied. It was determined that the reinforcement effect of ultrasound originated from physical change caused by cavitation via catalyst -free experiment, then the impacts of reaction temperature, ultrasonic power and position of ultrasound field on transesterification were researched. The optimal reaction temperature was determined as 45℃ through comprehensive con-sideration of system activity and cavitation intensity, and the optimal ultrasonic power was determined as 100 W through comprehensive consideration of intensity and concentration of sound field;when the phase interface of reactants was nearby the position of standing wave in the sound field ( 30 mm distance from the bottom of ultrasound tank) , the transesterification was effectively promoted,and the conversion rate of biodiesel could reach 99. 64% in 5 min under the optimal conditions.%选用脱色处理后的煎炸废油为原料(酸值(KOH)4.20 mg/g,水分及挥发物0.072%,皂化值(KOH)197.24 mg/g,平均摩尔质量871.82 g/mol),KOH作为催化剂,采用超声波辅助制备生物柴油,并利用气相色谱对生成物进行分析测试。在前期实验得到反应条件为醇油摩尔比6∶1,催化剂用量为原料油质量1%的基础上,考察超声波对酯交换过程的强化作用。通过无催化剂实验确定超声波强化作用源于空化引起的物理变化,而后研究了反应温度、超声波功率、超声场位置对酯交换反应的影响。通过综合考量体系活性与空化强度得到最佳反应温度为45℃,通过综合考量声场强度及其集中性得到最佳功率为100 W,当反应物相界面处于声场驻波位置即30 mm处,可有效促进酯交换反应的进行,在最佳实验条件下反应5 min,生物柴油转化率可达99.64%。