甘油三乙酸酯超临界酯交换反应及其动力学研究

研究了在超临界条件下甘油三乙酸酯与甲醇或乙醇的酯交换反应,分别考察了超临界状态下醇油摩尔比和温度对反应的影响。实验结果表明,甲醇或乙醇与甘油三乙酸酯的摩尔比为14、反应温度为350℃、反应时间为20m in时,乙酸甲酯或乙酸乙酯的收率分别达100%和60%。对超临界状态下动力学的研究结果表明,甘油三乙酸酯与甲醇或乙醇的酯交换反应为拟一级反应,在相同的反应条件下,采用甲醇时酯交换反应速率比用乙醇时快,相应的甘油三乙酸酯的转化率也高;甘油三乙酸酯在超临界甲醇或乙醇中酯交换反应的表观活化能分别为58.7 kJ/mol和75.1 kJ/mol,甘油三乙酸酯与甲醇酯交换反应的活化能低于与乙醇酯交换反应的活化能,表明碳链短的醇更易进行酯交换反应。

Kinetics of Transesterifications of Triacetin with Methanol or Ethanol Under Supercritical State

Non-catalytic transesterification of triacetin with methanol or ethanol under supercritical state was investigated.The products were analyzed by means of high performance liquid chromatography.Yields of methyl acetate and ethyl acetate were 100% and 60% respectively,under adopted reaction conditions: mole ratio of alcohol to triacetin 14,reaction temperature 350℃ and time 20min.Kinetics of non-catalytic transesterification of triacetin was studied in supercritical methanol or ethanol.The reaction was assumed to be a pseudo first order reaction under supercritical state.It seemed that reaction rate and product yield in methanol were faster and higher than those in ethanol.Apparent activation energies of reactions were 58.7kJ/mol and 75.1kJ/mol in methanol and ethanol,respectively,which indicated the above transesterification reaction was easier to be carried out in methanol than in ethanol.