The Stirring Effect on the Crystal Morphology of p-Acetamidobenzoic Acid Solution Crystallization

Abstract

This work investigates the stirring effect on p-Acetamidobenzoic Acid (p -AABA) crystal morphology through single crystal cultivation, crystal face growth rate, and nucleation supersaturation measurements, molecular simulation (MS), and computational fluid dynamics (CFD). Results show that stirring rate influences nucleation supersaturation, boundary layer thickness on the {101} and {010} faces, and shear stress applied on these two faces. This leads to changes in nucleation rate, nucleus size, and relative growth rates between the {101} and {010} faces, thus affecting crystal morphology. Under low-rate stirring (150 rpm), crystals exhibit a small size, a low aspect ratio, and a clear aggregation phenomenon. Appropriately increasing stirring rate can prevent aggregation and improve particle size and crystal aspect ratio. High-rate stirring leads to a higher shear stress at the corner points of the {101} face, causing crystal fragmentation, which leads to a significant decrease in crystal size and a slow decrease in aspect ratio. Moreover, the growth rates of the {101} and {010} faces exhibit an exponential dependence on supersaturation. The {101} face grows faster than the {010} face, and this growth rate difference widens with the increasing supersaturation. This study provides a theoretical basis and practical guidance for optimizing crystal morphology in stirred solution crystallization.