酶法制备生物柴油的酯交换反应动力学

A Kinetic Study on Lipase-catalyzed Production of Biodiesel

采用气相色谱法,以叔丁醇作为反应介质,大豆油作原料,在不同温度下测定固定化脂肪酶Novozyme 435催化的甲醇醇解反应动力学.利用乒乓(BiBi)机制和King-Altman图形法来建立反应的反应机理和动力学模型,并通过软件拟合,计算出了该反应的表观速率常数、最大反应速率以及相关热力学参数.结果表明该反应过程分两步进行,第一步反应是甘油三酸酯与脂肪酶形成酰基化酶复合物,其活化能大于第二步反应,即酰基化酶与甲醇的反应.且随着温度的升高反应速率随之增大,但增大的幅度逐渐减小,其主要原因是该反应过程的活化能较小,所以在较高温度时,提高温度对反应速率的影响不是很大.

By means of gas chromatography, the kinetic of transesterification of soybean oil with methanol catalyzed by immobilized lipase Novozyme 435 in tert-butanol as a reaction medium was investigated. Reaction mechanism and kinetic model were based on ＂Ping Pong Bi Bi＂ mechanism and King-Altman graphic method. The apparent rate constants, maximum reaction rate and relational thermodynamic parameters were calculated using computer software. The results showed that there were two steps in the lipase-catalyzed transesterification in organic phase. Firstly, triglyceride and lipase form acylated enzyme complexes, whose activation energy is higher than the second step which is the reaction between acylated enzyme and methanol. Also, faster the reaction rate is as the temperature rise, but increment decreases gradually. It is main reason that the activation energy of reacts are small, so the temperature has a little influence on the reaction rate in high temperature.