Separation of Complex Feed Streams of a Product by Layer Melt Crystallization

The purification of a complex feed stream of a multicomponent product, i.e., two isomers and impurities, by melt crystallization was evaluated by studying different optimization parameters like crystal growth rate, crystallization time, and purity. First, a phase diagram was established and on this basis different crystallization experiments were carried out. A laboratory‐scale solid layer melt crystallizer, a so‐called cold finger, was used to determine the purity and separation of the components, i.e., the ratio of the components, from the product at different crystallization times and temperatures as a function of layer thickness and a sweating process. The desired composition of the final product was achieved by adding components resulting from the second stage of crystallization since the first crystallization gave only the desired purity but not the right mixture of the two compounds of the wanted product. A mixture of complex material was separated by a simple layer melt crystallization technique to achieve maximum purity which to date is not possible by distillation. Two isomers were separated in different crystallization steps and the purified materials were remixed together. For a high purification demand, melt crystallization can be applied as an alternative to distillation.