A new melt crystallization process for efficient purification of chlorobromobenzene

Abstract

O-chlorobromobenzene and some other impurities are easily introduced during the synthesis of p-chlorobromobenzene, which results in the higher impurity content and lower product purity. What’s more, p-chlorobromobenzene and o-chlorobromobenzene are isomers of each other, which brings the high similarity of their physical and chemical properties, thus the conventional separation methods do not work efficiently. A melt crystallization was carried out in this work to explore the separation and purification process of chlorobromobenzene. The influences of the cooling rate, final crystallization temperature, and crystal growth time were examined systemically based on the following criteria: the distribution coefficient, crystallization yield and purity. At last, the optimal process conditions for the separation of p- and o-chlorobromobenzene were reached at the cooling rate of 0.2 °C/min, the final crystallization temperature of −2 °C, and the crystal growth time of 5 h. The final yield was 62.74%, the purity was 99.15%, and the distribution coefficient was 0.0166, which indicated that the optimal process conditions can effectively separate the mixture of o-chlorobromobenzene and p-chlorobromobenzene. The above results indicated that the melting crystallization process was an efficient separation and purification method for chlorobromobenzene.