The Agglomeration of Niacin Crystals in the Cooling Crystallization Process

Crystal agglomeration is an important factor that can affect the purity and crystal habit of crystalline products. Agglomeration of niacin crystals in its cooling crystallization and its mechanism is investigated using both experimental and molecular dynamics simulation methods. The magnitude of the interaction energy which is mainly contributed by the hydrogen bond and π–π stacking between the (0 1 1) crystal face and (1 1 −1) crystal face that have both the pyridine and carboxyl groups is the main factor determining the extent of agglomeration of niacin crystal. Besides, the interaction energy increases with the crystallization temperature and the supersaturation of the solution, and hence the agglomeration is more severe. The change of solvent species has minimal effect on the agglomeration of crystals. Besides, the agglomeration situation of carbamazepine and acetaminophen that with similar structures to niacin is also verified using molecular dynamics simulations. The findings in this work can be used to predict, control the agglomeration phenomenon, and optimize the crystallization process of niacin and other substances with similar chemical structure.