Solid–liquid equilibria of mixtures containing tert-butanol, m-chlorophenol, and p-chlorophenol and development of adductive crystallization processes

Abstract

The solid–liquid equilibria data of the ternary system consisting of tert-butanol (A), m-chlorophenol (B), and p-chlorophenol (C) and the three constituent binary systems were experimentally studied by means of the solid-disappearance method. The binary system consisting of m-chlorophenol and p-chlorophenol was observed to exhibit one eutectic point. However, the tert-butanol + m-chlorophenol and tert-butanol + p-chlorophenol mixtures behave differently, each exhibiting two eutectic points and one congruent melting point; the mole fraction of tert-butanol in the congruent melting complexes, which are represented, respectively, by the formula A 2B and A 2C, are 0.6602 and 0.6690. All the experimental melting temperature data can be satisfactorily represented by the empirical equations of Ott and Goates. Several ternary mixtures with specified mole ratios of m-chlorophenol to p-chlorophenol (pseudo-binary mixtures) were also studied. They all exhibit two eutectic points and one congruent melting point near the tert-butanol mole fraction of 0.6667. This implies that the mixtures of the congruent melting complexes A 2B and A 2C were formed during freezing. A ternary phase diagram showing the projections of all eutectic and congruent melting points is prepared. Based on the information contained in this diagram, a conceptually feasible process using tert-butanol as an adductive agent is proposed to separate the eutectic mixture of m-chlorophenol and p-chlorophenol.