氧化钙/氧化镁催化菜籽油与甲醇酯交换反应动力学的研究

在固体碱 CaO/MgO 催化下,以精制菜籽油与甲醇为原料进行酯交换反应制备了生物柴油,用气相色谱法跟踪分析生物柴油(脂肪酸甲酯)的含量,考察生物柴油中脂肪酸甲酯的生成动力学。结果表明,反应速率动力学方程分3个阶段:反应开始为引发阶段,酯交换反应速率对菜籽油浓度为0.5级,逐步转变为增长阶段的2级反应,最终反应达到平衡阶段。脂肪酸甲酯引发阶段反应活化能为76.77 kJ/mol,频率因子为9.80×10~7(mol/L)~(0.5)/min;增长阶段反应活化能为29.31 kJ/mol,频率因子为6.19×10~3L/(mol·min)。该研究为固体碱催化菜籽油与甲醇酯交换反应的动力学提供了理论基础。

KINETICS OF TRANSESTERIFICATION OF RAPESEED OIL BY METHANOL CATALYZED BY SOLID BASE CATALYST CALCIUM OXIDE/MAGNESIUM OXIDE

The purpose was to discuss the formation kinetics of bio-diesel prepared by solid base cataly- sis.With refined rape oil and methanol as raw materials,solid base CaO/MgO as catalyst,the bio- diesel was prepared by transesterification of rape oil and methanol under solid base catalysis and the bio-diesel(fatty acid methyl ester)content was traced and analyzed by gas chromatograph so as to in- vestigate the kinetics of component fatty acid methyl ester in bio-diesel.The kinetics research showed that the velocity equation of transesterification of rape oil and methanol catalyzed by solid base CaO/ MgO was(-r_A)=dC_p/dt=kC_A~2.The kinetics research of reaction velocity was divided into three sta- ges.The reaction started as initial stage,the transesterification reaction of the initial stage which is 0.5-order with respect to rapeseed oil,gradually transformed to be the second grade reaction of in- crease stage and finally reached balance stage.The activation energy of the initial stage of the transes- terification was 76.77 kJ/mol and the frequency factor is 9.80×10~7(mol/L)~(0.5)/min,and 29.31 kJ/ tool and 6.19×10~3 L/(mol·min)respectively for the latter two stages of the transesterification.The research provided theoretical basis for the kinetics of the transesterification of rape oil and methanol catalyzed by solid base.