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Abstract

The precipitation of organic particles from supercritical fluids (SF) by expansion (SFX) has become an interesting alternative to milling without thermal decomposition. Through the rapid expansion process, a dramatic change of the solute supersaturation ratio is created causing subsequent precipitation with a narrow particle-size distribution. It was found that β-carotene precipitates from SF ethylene and ethane have the feed material crystallinity. However, SF CO2 reacted with β-carotene and did not give characteristic β-carotene X-ray spectra. The mean particle sizes of these precipitates were in the submicron range (ca 0.3 μm). Increased solubility was obtained by addition of toluene as cosolvent in SF ethylene. It was found that the mean size of β-carotene particles, generally remained unchanged if the toluene concentration was less than 11/2 mol %. The SFX process appears to be in a single fluid phase when up to 11/2 mol % toluene cosolvent is used.