Separation of ternary mixtures by extractive distillation with 1,2-ethandiol and glycerol

Abstract

Continuous extractive distillation is a widely used method to separate binary and multicomponent azeotropic mixtures. Large-scale application and heavy energy usage play an important role in discovering more efficient separating agents. Separating agent (entrainer) selection for extractive distillation of binary mixtures is usually based on the analysis of relative volatility diagrams of components to be separated. Selective effect of entrainer is due to the differences in character and intensity of intermolecular interactions between entrainer and original mixture compounds. Accordingly, it is reasonable to additionally evaluate excess Gibbs energy magnitudes in binary systems formed by compounds of original mixture and entrainer (Raeva et al., 2011a).Separating agent selection based on thermodynamic criterion is not uniquely defined for ternary mixtures yet. It establishes some steps of entrainer choice for extractive distillation of ternary mixtures containing several azeotropes. Substantiation of entrainer efficiency is proved by separation of industrial mixtures: tetrahydrofuran–methanol–water, ethyl acetate–ethanol–water and acetonitrile–methanol–water.1,2-Ethandiol is well known to be an effective entrainer for different type of systems, including aqueous mixtures of organic substances (Gomez and Gil, 2009; Frolkova and Raeva, 2010). Glycerol is becoming more embroiled into separation processes due to environmental issues. They both fill in the common requirements for entrainer: by sufficiently changing the relative volatility of the substances to be separated and avoiding formation of new azeotropes with components of separating mixtures.