超声波辅助下脂肪酶催化高酸值废油脂制备生物柴油

Lipase-catalyzed Production of Biodiesel from High Acid Value Waste Oil with Ultrasonic Assistant

摘要:

探讨了超声波辅助条件下脂肪酶催化高酸值废油脂转化为生物柴油的反应。来源于Aspergillus oryzae和Candida antarctica的固定化脂肪酶，在超声波辅助下，对高酸值废油脂转化为生物柴油具有高的催化活性。以来自于C. antarctica的固定化脂肪酶Novozym435为催化剂，以酸价为157mg KOH/g的高酸值废油脂为原料在超声波辅助下与丙醇反应，在脂肪酶用量为油质量的8%、初始醇油摩尔比为3∶1、反应温度控制在40～45℃、超声波频率和功率分别采用28kHz和100W的条件下，反应50min转化率达到94.86%。在此条件下，不同碳原子数（C₁～C₅）的直链和支链醇均有较高的转化率，在短链醇的选择上具有宽广的适应性。超声波还减少了反应产物和反应体系中其他黏性杂质在固定化脂肪酶表面的吸附，回收的Novozym435相较单纯机械搅拌条件下回收的外观干净、分散良好无结块现象、易于洗涤和再次利用，具有良好的操作稳定性。

Abstract:

Biodiesel fuel produced with the enzyme-catalyzed esterification and transesterification of high acid value waste oil through ultrasonic assistant was explored. Propyl oleate, biodiesel, converted from high acid value waste oil and 1-proponal catalyzed with immobilized lipases from Candida antarctica and Aspergillus oryzae in conditions of ultrasonic assistant. Commercial immobilized lipase Novozym 435 from C. antarctica was used as biocatalyst catalyzing high acid value waste oil and 1-proponal esterification and transesterification to propyl oleate under the ultrasonic assistant conditions and different conditions such as lipases amounts, initiatory molar ratio of propanol to oil, frequency of ultrasonic and power of ultrasonic were investigated and optimized. It is revealed that the enzymatic activity of Novozym435 is enhanced and, in particular, enzyme-catalyzed transesterification activity is enhanced obviously under the ultrasonic assistant conditions. Low frequency and mild energy ultrasonic is a key factor for enhancing enzymatic activity, emulsifying oil-propanol system and accelerating the speed of produce diffusing in the system. Under the optimal ultrasonic assistant reaction conditions, such as Novozym435 amounts 8% by oil quantity, initiatory molar ratio of propanol to oil 3:1, frequency of ultrasonic 28 KHz, power of ultrasonic 100 W and temperature of water batch 40～45℃, the conversion ratio to propyl oleate reached to 94.86% in 50mins in comparison with the highest conversion ratio to propyl oleate 84.43% under the conventional mechanical agitation conditions. Furthermore, it is demonstrated that various short chain linear and branched alcohols (C₁～C₅) show high conversion ratio to fatty acid alkyl esters (biodiesel) under the optimal ultrasonic assistant reaction conditions. On the other hand, ultrasonic energy is propitious to reduce the adsorption of product propyl oleate, by-product glycerol and other emplastics in system on the surface of immobilized lipase Novzym435 and recyclable Novozym435 possess clean appearances, well decentralizations, no agglomeration and easy washing and well operational stability.