N,N-二甲基甲酰胺+醇二元混合物的黏度测定与关联

Measurement and correlation of viscosities of binary mixtures of N,N-dimethylformamide with ethanol,propanol,ethylene glycol or 1,2-propanediol

在288.15~313.15 K和常压下,利用乌氏黏度计测定了N,N-二甲基甲酰胺(DMF)分别与乙醇、丙醇、乙二醇和1,2-丙二醇组成的二元系全浓度范围内的黏度,计算了过量黏度Δη和过量流动活化自由能ΔG*E。用Redlich-Kister方程对过量黏度进行了关联;用黏度模型如Frenkel方程,Grunberg-Nissan方程,Katti-Chaudhari方程和McAllister方程对实验黏度数据进行了关联和预测,并利用Eyring理论方法计算了流动活化自由能、活化焓和活化熵等热力学函数。结果表明,4个二元系的过量黏度和过量流动活化自由能均为负值,且都随温度降低而偏差增大。过量黏度最低值均发生在DMF摩尔分数约为0.3处。McAllister模型对黏度数据的关联结果最好,预测值与实验值的平均相对偏差最小。比较并分析了DMF与一元醇和二元醇之间分子相互作用的差异。。

The viscosities of binary mixtures consisting of ethanol,propanol,ethylene glycol or 1,2-propanediol with N,N-dimethylformamide（DMF） were determined for the whole range of compositions at 288.15—313.15 K under atmospheric pressure by using Ubbelohde viscometer.The excess molar viscosity（Δη） and excess Gibbs energy of activation of viscous flow（ΔG＊E） were calculated from the experimental data,and correlated by Redlich-Kister equation.The viscosities of binary mixtures were correlated and predicted with four different expressions（Frenkel,Grunberg-Nissan,Katti-Chaudhari and McAllister model）.It has been using the theory of Eyring method to calculate the thermodynamic functions of activation of viscous flow,such as the flow activation free energy,the activation enthalpy and entropy.The results show that both Δη and ΔG＊E are negative over the whole mole fraction range in the temperature range studied for all of the binary mixtures,and the deviation is greater as temperature decreases.All the viscosity deviations reached the minimum values at x1（DMF）≈0.3.The three-body McAllister semi-empirical equation was found to be the best correlation to represent the viscosities of all binary mixtures,in which the average relative errors between predicted and experimental data were minimum.The differences of intermolecular interaction between monohydric and dibasic alcohol with DMF were compared and analyzed.