A Simple Method to Predict and Interpret the Formation of Azeotropes in Binary Systems Using Conventional Solvation Free Energy Calculations

Simple expressions are presented to determine if a binary system will exhibit a minimum or maximum boiling azeotrope using conventional free energy calculations using molecular simulation or electronic structure calculations in a continuum solvent. The expressions compare the solvation free energy of each component at infinite dilution relative to itself, requiring four total solvation free energy calculations per binary system. The solvation free energies can be related to intermolecular interactions and, therefore, shed insight into why an azeotrope occurs. The application of the expressions is demonstrated for 2366 binary systems using solvation free energies computed using electronic structure calculations in the SM12, SM8, and SMD universal solvent models. The overall success rate for predicting the correct phase behavior was 0.718, 0.711, and 0.685 for SM12, SM8, and SMD, respectively.本文提出了若干简洁表达式，用于通过分子模拟或连续溶剂环境下的电子结构计算所开展的常规自由能计算，判断二元体系是否会形成最低沸点共沸物或最高沸点共沸物。 该表达式通过对比各组分在无限稀释条件下相对于自身的溶剂化自由能（solvation free energy），每个二元体系共需完成四次溶剂化自由能计算。 溶剂化自由能可与分子间相互作用建立关联，进而阐明共沸物的形成机理。 本文针对2366个二元体系，采用SM12、SM8与SMD通用溶剂模型下电子结构计算所得的溶剂化自由能，验证了该表达式的实际应用效果。 针对相行为的预测准确率，SM12、SM8及SMD模型分别达到0.718、0.711与0.685。