Preparation of anthracene fine particles by rapid expansion of a supercritical solution process utilizing supercritical CO2

Abstract

The rapid expansion of a supercriti cal solution (RESS) process is an attractive technology for the produc- tion of small, uniform and solvent-free particles of low vapor pressure solutes. The RESS containing a nonvolatile solute leads to loss of solvent power by the fast expansion of the supercritical solution through an adequate nozzle, which can cause solute precipitation. A dynamic flow apparatus was used to perform RESS studies for the preparation of fine anthracene particles in pure carbon dioxide over a pressure range of 150-250 bar, an extraction temperature range of 50-70 o C, and a pre-expansion temperature range of 70-300 o C. To obtain fine particles, 100, 200 and 300 µm nozzles were used to disperse the solution inside of the crystallizer. Both average particle size and particle size distribution (PSD) were dependent on the extraction pressure and the pre-expansion temperature, whereas extractor temperature did not exert any significant effect. Smaller particles we re produced with increasing extraction pressure and pre- expansion temperature. In addition, the smaller the nozzle diameter, the smaller the particles and the narrower the PSD obtained.