Role of phase behavior and atomization in the supercritical antisolvent precipitation

An experimental study on supercritical antisolvent (SAS) precipitation has been performed to gain insight into the role of phase behavior and atomization in controlling morphology and dimension of precipitates. The mixture yttrium acetate/dimethyl sulfoxide has been used as the main model system and supercritical CO2 has been used as the antisolvent. Two SAS apparatuses (laboratory and pilot scale) with two injector arrangements and operating with various injector diameters in the range 60-500 mum have been used. The results showed that operating above the mixture critical point (MCP) of the ternary mixture yttrium acetate/dimethyl sulfoxide/ carbon dioxide, sub-micrometric particles are generated nearly independently from the size of the injector and of the apparatus. We also demonstrated that it is possible to modify the particle dimension by simply changing the operating pressure and/or temperature in the vicinity of the MCP. The use of a pseudo-binary diagram pressure-molar fraction has been proposed as a base framework to explain the relationship between the particle morphology and the phase behavior of processed mixtures. Particularly, we have shown that the single-phase region in the gas-rich side of the pressure-composition diagram and below the MCP can be usefully explored to modify the particle dimensions of the precipitate.