Theoretical and experimental investigations of the micronization of organic solids by rapid expansion of supercritical solutions

The RESS-Process (Rapid Expansion of Supercritical Solutions) is an innovative and promising technology to produce small particles and offers interesting applications for difficult-to-comminute species such as certain pharmaceuticals. Our RESS-experiments are carried out with an apparatus suitable for temperatures up to 600 K and pressures up to 60 MPa. Carbon dioxide (CO2) and trifluoromethane (CHF3) have been used as supercritical solvents and cholesterol and benzoic acid as solutes. Besides the experimental investigations, the RESS-Process is modelled numerically considering the three parts capillary inlet–capillary–microscale free jet. The evolution of fluid pressure and temperature along the expansion path are used to calculate the supersaturation of the real mixtures CO2/cholesterol, CO2/benzoic acid and CHF3/benzoic acid and the respective nucleation rates. The results of these calculations are theoretical nucleation rates of about 1026 cm−3 s−1 at residence times of 10−7 s in the free jet.