Separation of Aromatic Compounds Using Retrograde Crystallization in Supercritical Fluid

T. Sako, M. Sato, H. Takato, and M. Kato
[Journal of the Japan Petroleum Institute, Vol. 39, pp. 12-19, 1996]

We measured the solubilities of pure solids of anthracene, fluorene, acridine, and binary solid mixtures of phenanthrene + anthracene, fluorene + acridine in supercritical CO₂ to determine the appropriate conditions for purification of polycyclic aromatics or heterocyclic compounds using a retrograde crystallization technique. Moreover we attempted to separate specific compounds from these two solid mixtures. As a result, it was found that (1) the crossover region of 2 kinds of solid mixtures in supercritical CO₂ was sufficiently wide to isolate the solid component from the mixture; (2) the Peng-Robinson equation of state gave good predictions for solubilities of pure solids but gave poor predictions for those of the solid mixtures in supercritical CO₂; and (3) phenanthrene, fluorene and acridine of high purity were separated from the solid mixtures, but anthracene was not, as its amount predicted from the solubility data was very small.