Accession Number : ADA317611

Title :   Particle Formation During the Expansion of Supercritical Solutions.

Descriptive Note : Final technical rept. 1 Aug 93-31 Jul 96,

Corporate Author : PRINCETON UNIV NJ DEPT OF CHEMICAL ENGINEERING

Personal Author(s) : Debenedetti, P. G.

PDF Url : ADA317611

Report Date : 27 SEP 1996

Pagination or Media Count : 17

Abstract : Two techniques were used to study the formation of particles from supercritical fluids. In the rapid expansion of supercritical solutions (RESS), solutes were dissolved at high pressure and precipitated by decompression across a flow restriction device. In the supercritical antisolvent process (SAS), the supercritical fluid acted as an antisolvent towards solutes dissolved in an organic-solution. RESS experiments with poly (L-lactic acid) (L-PLA) as solute showed that decreasing the density of the solvent at the exit of the expansion device caused precipitation of small and irregular L-PLA particles to occur inside the expansion device. Larger microspheres were formed at higher exit density. Encapsulation of pyrene in L-PLA microspheres was achieved by varying the initial amounts of pyrene and L-PLA present. SAS was used to make microfibers of aromatic polyamides and protein particles in the 1-5 micron size range. The protein particles retained their biological activity upon redissolution in water. The thermodynamics of mixed solute precipitation from a supercritical solution was investigated by calculating the retrograde regions of several polynuclear aromatic compounds in a supercritical solvent. The size of the retrograde region was found to decrease as the solute's heat of sublimation increased.

Descriptors :   *SOLUTIONS(MIXTURES), *PARTICLES, *SUPERCRITICAL FLOW, DENSITY, FIBERS, PHASE TRANSFORMATIONS, THERMODYNAMICS, HIGH TEMPERATURE, PROTEINS, POLYAMIDE PLASTICS, HIGH PRESSURE, PRECIPITATION, SOLUTES, SOLVENTS, EXPANSION, AROMATIC COMPOUNDS, CARBON DIOXIDE, DISSOLVING, DECOMPRESSION, LACTIC ACID, HEAT OF SUBLIMATION, MICROSPHERES.

Subject Categories : Physical Chemistry
      Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE