Crystallization of Organic Compounds, 2nd Edition

Chapter 4Kinetics

As noted in previous chapters, important information is obtained by equilibrium measurements and correlations regarding a given crystallization process. However, much of the effort expended in developing and designing such a process is dedicated to defining the rate processes involved. This chapter presents a brief discussion of the rate processes which define the nature of the final crystalline product and, of course, the equipment required to produce it.

Kinetics of nucleation and crystal growth can be modified to some extent to favor an efficient process, but in almost all commercial crystallization processes, this flexibility is limited by the needs of the users of the product.

In the pharmaceutical industry, the users of bulk final products are the dosage form formulators, who must provide a product which will produce the desired beneficial effect on patients health. As can be imagined, purity, and bioavailability criteria must be satisfied before the formulators can address concerns about other crystal properties such as flow‐ability, compaction properties, and other parameters.

Users of intermediate products (those who carry out the next step) are always concerned with levels of impurities being carried forward to them from the previous crystallization process, but generally they have fewer concerns about other properties of the solids. This can often allow manipulation of process parameters to favor reduced time cycles or more efficient types of processing ...