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Crystallization and precipitation processes are used in the chemical and pharmaceutical industry to produce crystals with desired product properties, such as flowability, filterability, drying time and bioavailability. These properties are greatly affected by the particle size distribution and control of it is one of the major goals in process design. Model-based design approaches require accurate kinetics and thermodynamic data. Therefore, the focus of this thesis is on the development of protocols for the measurement of nucleation, growth, agglomeration and polymorph transformation kinetics as well as on the development of suitable models for process design and optimization. Three different crystallization and precipitation processes are investigated: pH-shift precipitation of L-glutamic acid, combined cooling/antisolvent crystallization of acetylsalicylic acid and antisolvent precipitation of L-asparagine. Depending on the intrinsic kinetics of the substance and on the operating conditions different experimental methods for the determination of the kinetics have to be applied. If the kinetics are relatively slow the experiments can be carried out in a stirred tank reactor. FBRM, ATR-FTIR and Raman spectroscopy are used for process monitoring. Kinetics are determined based on crystallization experiments by a combination of a population balance model and an integral parameter estimation technique. The process models are used for process design and optimization. If the characteristic time scale of precipitation is similar to or shorter than the one of mixing in a stirred tank, alternative equipment is required to avoid transport limitations and the associated effect on the particle size distribution. This problem can be overcome using efficient mixing devices, such as static micromixers. The mixing efficiencies of two static mixers with different geometries are characterized using competitive-parallel chemical reactions and computational fluid dynamics (CFD). Finally, the mixer setup is used to determine nucleation and growth kinetics at high supersaturations and to conduct continuous precipitation experiments.

Optimizing the precipitation of organic compounds