CO2 partial density distribution during high-pressure mixing with ethanol in the supercritical antisolvent process

A two-dimensional Raman scattering technique was used to locally and temporally resolve the effect of the mixture formation process on the carbon dioxide (CO2) partial density distribution in the pulsed supercritical antisolvent (SAS) process. The solvent ethanol was injected into the antisolvent CO2 in the vicinity of the binary mixture critical pressure (MCP). The acquired Raman images were converted into CO2 partial density distributions. For pressures far above the MCP, CO2 partial densities were not affected by the presence of the injected ethanol in the operational sphere of the jet. For pressures slightly below the MCP, CO2 partial densities were measured three times higher in the operational sphere of the ethanol spray than in the surrounding bulk region. To reach equivalent CO2 partial densities far above the MCP, chamber pressures as high as 100 MPa would be necessary.