Interactions of phase equilibria, jet fluid dynamics and mass transfer during supercritical antisolvent micronization

Hydrodynamics Influence on Particles Formation Using SAS Process

“…The transition between these two phenomena depends on the operating pressure, but also on the viscosity and the surface tension of the solvent. Reverchon et al demonstrates that in the case of dimethyl sulfoxide (DMSO) at pressures larger than the MCP a progressive transition exists between multi-phase and single-phase mixing, but is not observed, even for pressures very close to the MCP, in the case of acetone (Reverchon et al, 2010). In the dripping mode, the droplet size decrease with increase in pressure operation due to a corresponding decrease in the interface tension, so the initial droplet size can be manipulated by small changes in the pressure of CO 2 .…”

“…Surface tension decreases to zero in a shorter distance than characteristic break-up lengths. Thus, the jet spreads forming a gaseous plume and will be characterized by the degree of turbulence associated with the vortices produced in the SC CO 2 (Chehroudi et al, 2002;Kerst et al, 2000;Reverchon et al, 2010). Lengsfeld et al were the first group that investigated fluid dynamics of the SAS process, studying the evolution and disappearance of the liquid surface tension of fluids injected in supercritical carbon dioxide.…”

“…In this way Reverchon et al used light scattering technique to clearly differentiate between an atomized very droplet laden spray and a dense "gasplume", limitation which cannot be gained by applying optical techniques due to the fact that both the droplet laden spray and the dense "gas-plume" result in a dark shadow (Reverchon et al, 2010). On the other hand, extensive research has been done using scanning electron microscopy (SEM) to evaluate the size and morphology of particles formed under supercritical conditions (Armellini& Tester, 1994;Bleich et al, 1994;Mawson et al 1997;Randolph et al, 1993;Shekunov et al, 2001;).…”

“…It was demonstrated that there are limiting hydrodynamic conditions that must be overcome to achieve a dispersion of the liquid solution in the dense medium; this dispersion must be sufficiently fine and homogeneous to direct the process toward the formation of uniform spherical nanoparticles and to the achievement of higher yields (Tenorio et al, 2009). In this way, Reverchon et al (Reverchon et al, 2010, Reverchon& De Marco, 2011 tried to find a correlation between particle morphology and the observed jet, concluding that expanded microparticles were obtained working at subcritical conditions; whereas spherical microparticles were obtained operating at supercritical conditions up to the pressure where the transition between multi-and single-phase mixing was observed. Nanoparticles were obtained operating far above the mixture critical pressure.…”

“…For these reasons, the present review is focused on the investigation of the disintegration regime of the liquid jet into the supercritical (SC) CO 2 . There are many works where correlations between the morphologies of the particles obtained in the drug precipitation assays and the estimated regimes were established (Carretier et al, 2003;Reverchon et al, 2010;Reverchon& De Marco, 2011;Tenorio et al, 2009). It was demonstrated that there are limiting hydrodynamic conditions that must be overcome to achieve a dispersion of the liquid solution in the dense medium; this dispersion must be sufficiently fine and homogeneous to direct the process toward the formation of uniform spherical nanoparticles and to the achievement of higher yields (Tenorio et al, 2009).…”