Purification of 2,4-dinitrochlorobenzene using layer melt crystallization: Model and experiment

Abstract

• The final product reached 99.48% during multi-stage melt crystallization. • Effective sweating models can benefit the crystallization process evaluation. • The crystal packing structure can meet the fractal porous characters. In this study, layer melt crystallization was introduced to separate 2,4-dinitrochlorobenzene (2,4-DNCB) from the mixture of 2,4-DNCB and 2,6-DNCB. The multi-stages melt crystallization was used to achieve the ultrapure target product preparation, in which the final purity of 2,4-DNCB reached 99.94%. In the melt crystallization, several indicators including the fractal porous medium theory and separation performance modeling were introduced to evaluate the process behavior. The fractal porous medium theory including porosity and tortuosity were used to describe the inner crystal packing structure, quantitively. The separation performance parameters including distribution coefficient K c , and sweating yield Y S were investigated to describe the separation efficiency. Furthermore, the sweating number was used to describe the implicit relationship between separation results and sweating intensity. The sweating behavior was also modeled with two approaches to correlate the sweating time with separation performance. Final, a sweating model was established to estimate the purity C p ( t ) and yield Y ( t ) as a function of sweating time t and temperature T. Overall, layer melt crystallization is an effective approach to obtain ultrapure target products. The proposed parameters and models can describe and visualize the crystallization behavior successfully.