Model based experimental analysis for crystallization of DL-threonine in the presence of a chiral additive

The effect of additives and seeding on preferential crystallization of DL-threonine in water was studied performing experiments in a IL-batch crystallizer using L-glutamic acid as additive. For analysis online polarimetry and online density measurements were used in order to monitor the concentration trajectories of the two enantiomers over the whole experimental run. Particle size distributions were measured offline using a camera microscope and an automated image analysis software. A population balance model combined with nonlinear optimization was used to determine kinetic parameters for crystal growth and nucleation and to quantify the effects on particle size distribution. The use of milled seed material introduced the necessity to account for a change in crystal shape over time. By comparing the results of the findings to "benchmark" crystallization experiments without additive, it is possible to quantify the effect of the chiral additive and parameters of the seeds on the crystallization kinetics of DL-threonine in water.