Calorimetric transformation studies for crystal growth kinetics of benzoic acid in binary mixtures during cooling crystallization

Crystallization is an experimental phenomenon that does not always depend on predicted data for efficient processing. It, therefore, becomes important to conduct experiments in the seeded or unseeded crystallization process to gain insight into the growth kinetic parameters. The knowledge of the process and kinetic parameters is proved useful in developing strategies for the optimal design of crystallizers and in control of crystal size distribution. A differential scanning calorimeter (DSC) was used to perform isothermal growth experiments for seeded crystallization, and the kinetics was evaluated using a de-supersaturation curve. In order to get the de-supersaturation curve, the DSC heat flow signal was used to measure and quantify the mass change of seeds during the crystal growth process as a function of time at a particular temperature. Experiments were performed at temperatures ranging from 10 to 40 degrees C in sealed DSC pans. The growth order g was calculated from the isothermal experiments at varying temperatures, and the mass growth rate coefficient K-g, linear growth rate coefficient k(g), mass rate of crystal growth R-G and activation energy E-a of benzoic acid in the ethanol-water binary solvent were estimated from growth order g. The kinetic parameters were compared with the data obtained using online measurement techniques and found to be in good agreement. The present work establishes the reliability of calorimetric transformation studies for estimating growth kinetics using a small amount of sample in a very short period, at higher temperatures and pressures.