Abstract: The esterification of abietic acid with methanol was selected as a probe reaction.The thermodynamics of reaction was analyzed by group-contribution method.The reaction enthalpy, entropy, Gibbs free energy and equilibrium constant were calculated in the temperature range of 473—653 K and the pressure range of 0.1—20 MPa.The effects of temperature and pressure on the reaction were also discussed.The calculation indicates that the reaction enthalpy is -46.31—-10.10 kJ·mol^-1 and free energy is -53.26—-25.49 kJ·mol^-1, showing an exothermic and spontaneous reaction.The equilibrium constant is 136.32—748.89 at standard pressure and (1.1×10⁴)—(3.2×10⁴) in the range of 5—20 MPa.The experimental results show the conversion of abietic acid of 85.94%—94.89% and 73.80%—81.20% without catalyst in super/subcritical methanol, which is in agreement with thermodynamic calculation by the group-contribution method.

Key words: abietic acid, methanol, methyl abietate, group contribution, thermodynamic

摘要： 以枞酸为模型化合物、枞酸与甲醇的酯化为探针反应,采用基团贡献法对枞酸与甲醇酯化反应进行了热力学分析,计算了473～653 K、0.1～20 MPa反应体系的反应焓变、反应熵变、反应Gibbs自由能变以及反应平衡常数,探讨了温度与压力对酯化反应的影响。计算结果表明,反应的焓变为-46.31～-10.10 kJ·mol^-1,枞酸与甲醇的甲酯化反应为放热反应;反应Gibbs自由能变为-53.26～-25.49 kJ·mol^-1,反应为自发过程;标准压力下反应平衡常数为136.32～748.89,5～20 MPa下反应平衡常数为(1.1×10⁴)～(3.2×10⁴)。实验结果表明,在无催化剂条件下,超/亚临界甲醇与枞酸酯化反应的转化率分别为85.94%～94.89%、73.80%～81.20%,实验结果与基团贡献法热力学计算值相一致。

关键词: 枞酸, 甲醇, 枞酸甲酯, 基团贡献法, 热力学