FORMAÇÃO DE AZEÓTROPOS DO PONTO DE VISTA DA TERMODINÂMICA DE SOLVATAÇÃO

FORMATION OF AZEOTROPES FROM THE STANDPOINT OF SOLVATION THERMODYNAMICS

The formation of azeotropes is related to the deviation of the ideality of liquid mixtures. This deviation is expressed by the activity coefficient of each component. However, the physical origin of this behavior is not well quantified in terms of molecular interactions. In this work, a regular solution model was used, relating the β parameter to the solvation free energy of pure liquids in themselves and in the other component. A mathematical expression was derived that indicates when an azeotrope is formed. This equation shows that the greater the difference in vapour pressure between components, the greater the solvation difference of each liquid in itself and in the other component is needed to form the azeotrope. A set of 10 mixtures were randomly chosen and investigated as a test, and the equation worked in all cases.

Keywords:
Margules equation; liquid-vapour equilibrium; Redlich-Kister expansion; infinity dilution activity coefficient