气相色谱吸附过程的热力学函数变化及规律探讨——Ⅱ.吸附熵变的计算方程与硅胶对直链烷的吸附

Study of Thermodynamics Functions and Their Interrelationships in Gas Chromatographic Process——II.Discussion about Equations for Calculating Changes in Entropy of Adsorption of Alkanes on Silica Gel

前文报道Porapak对某些烷和醇吸附过程的热力学函数变化,并讨论了其中的一些规律.文中引用Atkinson等人提出的方程来处理实验结果:上述诸方程,有的所需数据难以直接由实验得到,有的则存在某些不妥之处.本文从吸附平衡的定义导出一个较为合理的方程,并据此计算了9个有机化合物在硅胶表面吸附过程的焓变和熵变.所得结果进一步验证了热力学补偿效应、同系物碳数关系和等热力学点等规律.

An equation for calculating changes in entropy and enthalpy of adsorption was derived from the adsorption equiliblium constant:In V-△H/RT+[△S/R+(?)n(RTS)]△H,△S,△G and ln K of adsorption of some alkanes and benzene on silica gel were calculated.The results show that the contributions of one molar methylene group to△H,△S,and△Gof adsorption were-4.4kJ/mol,-5.9kJ/mol·K,-2.7kJ/mol,respectively.Iso-thermodynamic point and thermodynamic compensation effect have also been found as in the case of Porapaks reported in the previous paper.