Recent Progress in Continuous Crystallization of Pharmaceutical Products: Precise Preparation and Control

Crystallization, as a solid–liquid separation process, is employed to purify and isolate a great diversity of crystalline pharmaceutical products. In recent years, continuous crystallization has attracted increasing attention because of the product and process robustness as well as higher productivity. In this work, we review the use of novel continuous crystallizers or modified conventional continuous crystallizers for the preparation of polymorphs, chiral enantiomers, solvates/hydrates, cocrystals, and spherical crystals. In addition, the theoretical framework and verification of the model-based control approaches are demonstrated. The application of process analytical technology tools in classical feedback loop control strategies in continuous crystallization is also discussed. Despite all this, the application of continuous crystallization still remains challenging because of the existence of drawbacks such as fouling and blockages. Therefore, a systematic discussion should be done before continuous crystallization is more widely applied.