水-乙酸二元体系汽液平衡的热力学性质分析

Analysis on Thermodynamic Properties for Vapor-liquid Equilibrium of Water-acetic Acid Binary System

用新型泵式沸点仪测定了在101.325kPa下水-乙酸二元系在不同液相组成时的沸点,用过量自由能函数Q,采用间接法由Tpx推算了水-乙酸二元系的汽相平衡组成y。汽相的非理想性用截至第二项的维里系数的状态方程求出汽相混合物中组分逸度系数。二元体系活度系数的关联分别用Wilson模型、NRTL模型、Margules模型和vanLaar模型进行关联,用最小二乘法求出了它们的液相活度系数模型参数。所得的液相活度系数来计算三个二元体系的过量吉布斯自由能函数GE/RT。计算的泡点温度与实验的所测得的沸点温度吻合良好,由面积积分法检验这些模型参数计算的二元体系相平衡数据得到很好的热力学一致性。

Isobaric vapor-liquid equilibrium （VLE） data at 101.325 kPa for the binary system containing water-acetic acid were determined by different liquid phase compositions using a novel pump-ebullionmeter. Values of fugacity coefficients for species i in vapor mixture were evaluated from the virial equation of state which was truncated to two terms according to non-ideal mixing rules. The vapor-phase compositions y had been calculated according to the Q function of molar excess Gibbs energy from Tpx by the indirect method. The activity coefficients γi of species i were correlated with the Wilson, NRTL, Margules and van Laar models through the least square method from the experimental T-x, and these parameters in turn are used to calculate vapor-phase compositions y. The activity coefficients are useful to calculate excess Gibbs function （G^E/RT） for the three binary systems. The calculated bubble point temperatures with the model parameters of activity coefficients were in good agreement with the experimental data. The thermodynamic consistency of the experimental data for the three binary systems was checked by area test method and was satisfactory.