Measurement of vapor-liquid equilibria for diethylamine + methanol system represented double azeotropy on elevated pressure

Abstract

Accurate phase equilibrium data can be used for the design and operation for separation processes based on phase behavior. An azeotrope is the mixture consists of two or more substances, the equilibrium vapor composition is equivalent to the liquid composition, and the equilibrium temperature (or pressure) indicates extreme value. If the mixture to be separated is an azeotropic system, no separation into pure components can be achieved by simple distillation. Knowledge of the acurate azeotropic data is necessity for chemical process synthesis. According to the Dortmund Data Bank [1], approximately 47% of the stored vapor-liquid equilibrium (VLE) data show azeotropic behavior. There are two types of azeotrope for binary systems, which are positive and negative azeotropes, generally. The binary system of diethylamine + methanol is known for the polyazeotropy at given temperature or pressure. The system forms a homogeneous maximum boiling azeotrope at 101.3 kPa. The second minimum boiling azeotropic point appears in the VLE at the condition of elevated pressure, around 300 kPa. Aucejo et al. [2] has measured the VLE at 101.3 and 300 kPa and discussed the detail of these phenomena thermodynamically. The purpose of this work is describing the trajectory of two different of azeotropic points on elevated pressure from experimental data.