Caffeine crystallization optimization and kinetics

Abstract

Caffeine is widely used in the chemical, food and pharmaceutical industries. Understanding their behavior during crystallization processes is of fundamental importance to elucidate the dynamics of crystalline growth. In this context, the present study aimed to investigate the variables that influence crystallization by reducing the temperature in saturated caffeine solutions, following the evolution of crystals during the aqueous crystallization phase. To achieve this purpose, a Central Composite Planning (PCC) was conducted with 18 experiments, in which supersaturation, agitation and crystallization time were analyzed in relation to the yield of the caffeine mass. The growth kinetics of the crystals were evaluated by quantifying the mass of the crystals and the concentration of the solution, as well as observing growth under an optical microscope. The average yield obtained at crystallization was 285.6%, and it is evident that the agitation exerted the greatest influence on the process yield, followed by supersaturation, while the crystallization time proved less significant. The responses indicated a crystalline growth of the seeds added in all the experiments of the PCC. In terms of kinetics, experimental data were correlated using the method proposed by Mullin. The results showed an increase in the mass of the crystals throughout the operation, however, the characteristic dimension decreased due to the acicular geometry of the caffeine crystals, which favors the longitudinal breakdown of the latter