Abstract
The batch cooling crystallization of the organic compound, ibuprofen, was carried out under 2.45 GHz microwave irradiation. n-Hexane containing a small amount of acetone (5 mol%) and Fluorinert™, which did not absorb microwave, were selected as the solvent and coolant circulating through the jacket of crystallizer, respectively. The ibuprofen-hexane solution was cooled from 40 to −1°C under microwave irradiation and no irradiation. When the solution was not irradiated to the solution, ibuprofen crystals appeared at 35°C. On the other hand, when irradiation with 300 W microwave was carried out, nucleation did not occur even when the solution temperature reached to −1°C. At that time, the supersaturation ratio was 9.5. Thus, crystal nucleation of ibuprofen was inhibited by the microwave irradiation. The effect of microwave irradiation continued for at least 100 min after the irradiation was stopped at −1°C. By adding a small amount of crystals to the highly supersaturated solution, small crystals with a narrow size distribution were produced.
