Finely‐divided powders by carrier solution injection into a near or supercritical fluid

Abstract

Abstract Carbon dioxide or ethane was used as an antisolvent medium from which organic solids dissolved in a liquid carrier solvent are precipated and collected as finely divided solids. Solid compounds of pharmaceutical interest, which are virtually insolute in the supercritical fluids per se, are efficiently obtained by injecting a solution of the solid into a volume of stirred supercritical fluid or compressed liquefied gas. A free‐flowing powder comprising very small particles ( > 5 μm) is obtained. Both continuous‐flow and batch operations were developed although he continuous‐flow operation is preffered. Process variable including temperature, pressure, stirring rate, injection concentration, and the rate and temperature of the carrier solution injection were studied to see how they affect the physical properties of the resultant product. Recovery (yield), particle size and uniformity, bulk powder density, microscopic apperance, and surface area were measured. Carbon dioxide and ethane antisolvents, several liquid‐phase injection solvents, and different solid compunds were studied. A simple unsteady‐state mathematical model of this CSTR precipitator is also presented.