| Summary: | Changes to crystallisation conditions can critically affect important physical properties of materials, which can in tum affect the sustainability of consistent product quality that is pivotal to industrial manufacturing. The following studies demonstrate how crystallisation processes, and the consequent quality of the crystals produced, can be easily manipulated by varying the solution mixing regimes and initial relative supersaturation. Most importantly, emphasis was given to changes to the material's physical properties induced by the presence of impurities in solution. To this effect, alpha-glycine crystals were crystallised using two different mixing regimes provided by an Oscillatory Flow Batched Baffled Crystalliser (OBBC) and an Impeller Driven Batch Crystalliser (IDBe). The relative initial supersaturation of glycine was also varied, at constant temperature, and fixed amounts of L-Phenylalanine (L-Phe) were added to doped solutions in order to probe the influence of impurities on glycine nucleation and crystalline quality. The crystallisation induction time, crystal size distribution and microstrain of alpha-glycine was increased by the presence of impurities and by decreasing the rate of hydrodynamic mixing. Higher initial supersaturations of glycine favoured quicker nucleation rates, smaller crystal size distribution and higher microstrains. The presence of L-Phe during the crystallisation of alpha-glycine did not induce the growth of different polymorphs (when performed at 20° C). However, doped solutions of alpha-glycine produced highly strained crystals with very different habit when compared to those grown from pure solutions. A qualitative explanation for the morphological differences in alpha-glycine pure and doped systems was suggested based on the crystal's molecular packing and possible solute molecule-crystal interface interactions. Key WordS: Crystallisation, Impurity, Habit, Oscillatory Flow Batched Bamed Crystalliser, Impeller Driven Batch Crystalliser, Alpha Glycine (a.-glycine), and L-phenylalanine (L-Phe).
|
|---|
