Continuous crystallization has gained interest in the pharmaceutical sector as part of the drive toward the transition from exclusive batch manufacturing to integrated continuous manufacturing in this industry. As a result, the design and operation of continuous crystallization processes for the preparation of pharmaceutical materials has been featured strongly in recent scientific literature. This review is an effort to gather together all of the published understanding on continuous crystallization with a pharmaceutical focus and to benchmark progress to date in realizing the potential benefits of transitioning this stalwart pharmaceutical unit operation from batch to continuous configurations.

The use of in situ tools to monitor the transformation of a polymorphic material has the potential to provide unique information about the mechanism and rate of transformation of the polymorphs. In this paper, the solution mediated transformation between α and β form p-aminobenzoic acid (PABA) was investigated in detail. Solubility of α and β form PABA in pure ethanol was also reported for the first time, allowing the accurate determination of the transition temperature of 13.8 °C. For the transformation experiments, Raman spectroscopy and Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy were used to in situ monitor the solid phase concentration and liquid concentration, respectively; Focused Beam Reflectance Measurement (FBRM) was used to in situ track the changes in the size and morphology of the particles. The observed changes were confirmed using PVM in-process imaging. It was proved by solubility data and transformation experiments that the relationship between α and β form is enantiotropic.

Heterogeneity of porous structures is an important material property involved during the design of adsorbents, catalysts and molecular recognition materials. This review discusses the mathematical methods that can characterize adsorption site energies and surface heterogeneity from the adsorption isotherms.

A novel process, sequential coupled‐batch diastereomeric crystallization is presented for the resolution of racemic mixtures. This strategy utilized a preferential crystallization of diastereomeric salt followed by sequential coupled diastereomeric salt resolution of racemic ibuprofen with the resolving agent (S)‐lysine utilizing a novel small scale pneumatic liquid exchange design to couple two batch crystallizers. Results were compared to conventional sequential resolution via seeded isothermal batch crystallization. Diastereomeric salt resolution was developed using the ternary phase diagram of the isolated (R)‐ibuprofen‐(S)‐lysine and (S)‐ibuprofen‐(S)‐lysine salts and optimized empirically with the aid of process analytical technology. Sequential coupled‐batch crystallization was found to be capable of increasing the yield of both salts while maintaining purity. This gave an increase in both the productivity and yield (20.5% for (S)‐ibuprofen‐(S)‐lysine) compared to the equivalent sequential batch (17.7% for (S)‐ibuprofen‐(S)‐lysine) crystallization methodology. Single crystals of the (S)‐ibuprofen‐(S)‐lysine were isolated, and its single crystal structure determined. © 2018 American Institute of Chemical Engineers AIChE J, 65: 604–616, 2019

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