乙酸乙酯酯缩合法合成乙酰乙酸乙酯的热力学分析

Thermodynamics analysis of ethyl acetoacetate synthesis from ethyl acetate by ester condensation

用Benson基团贡献法和Joback法对乙酸乙酯酯缩合法生成乙酰乙酸乙酯反应的焓变,吉布斯自由能和反应平衡常数进行了计算与分析。结果显示,在25～240℃内,反应的焓变均为正,说明此反应为吸热反应,随着反应温度的升高吸热量减少;反应的吉布斯自由能一直为正,理论上是不能自发进行的;该反应的平衡常数很小,但是随着温度的升高,平衡常数相应有所增大。要使反应顺利进行需加入适当的催化剂,而为了提高反应的转化率,可以采取升高反应温度,或在反应过程中移走生成物的手段使反应不断向所需方向进行。

The formation enthalpy, Gibbs free energy and equilibrium constant for the reaction of ethyl acetate condensation to ethyl acetoacetatewere estimated by Benson group contribution method and Joback method. The results showed that, in 25 to 240℃,the formation enthalpy is positive, which indicated that the reaction is endothermic, and the heat absorption capacity decreases with the rise of temperature; the Gibbs free energy is positive, which indicated the reaction could not occur spontaneously; and the equilibrium constant is small but increases with the rise of temperature. So it required adding suitable catalysts to let the reaction take place smoothly, raising the reaction temperature to increase the conversion, or removing the products from the reaction system to promote the positive reaction.