DefinePK

Abstract

Oiling out is a wanted effect during the cooling crystallization of complex molecules from solution: upon cooling, crystallization is preceded by the formation of a second liquid phase (Oiling out) which disturbs the crystallization process and often deteriorates the product properties. On the basis of the crystallization of 4,4' dihydroxydiphenylsulfone (DHDPS) from water/acetone, water/1-propanol and water/ethanol mixtures, respectively. This study proved the dependence of the oiling-out behavior on the solvent system. Attempts were made to model the oiling-out phenomenon using a thermodynamic equation of state here: (Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT)). Applying this model, an oiling-out behavior of the ternary system DHDPS/water/ethanol could be predicted qualitatively. Exchanging the water/acetone, water/1-propanol solvent mixtures by a mixture of water and ethanol led to a prevention of oiling out. This could be predicted by the calculations using PC-SAFT, as well as confirmed experimentally.