Influence of pressure, temperature and concentration on the mechanisms of particle precipitation in supercritical antisolvent micronization (original) (raw)
Related papers
New technologies for the precipitation of solid particles with controlled properties
2002
ABSTRACT Precipitation is a decisive unit operation for the production of fine particles with controlled properties. New technologies are developed in order to better control the production process. For example, sliding surface mixing device, vortex reactor or impinging jets may be cited. These reactors are studied in large intervals of operating conditions, showing therefore their possibilities and applications in precipitation. These new technologies are considered as “multifunctional”, because they allow in some ways the separation of the different mechanisms of precipitation (nucleation, growth, agglomeration, ripening). Thus, their contribution may be clearly identified in the control of the precipitation process and, particularly, their advantages in front of standard reactors.RésuméLa précipitation est un procédé décisif pour la production de solides divisés à propriété contrôlée. De nouvelles technologies sont développées, afin d’assurer une meilleure maı̂trise du procédé d’élaboration. A titre d’exemple, on peut citer le réacteur à disque tournant, le réacteur à effet vortex ou encore le dispositif de jets d’impact. Ces réacteurs sont étudiés dans une large gamme de conditions opératoires, montrant ainsi leurs possibilités et applications en précipitation. Ces nouvelles technologies sont considérées comme multi-fonctionnelles, car elles permettent dans une certaine mesure de découpler les différents mécanismes de la précipitation (nucléation, croissance, agglomération, mûrissement). On identifie ainsi clairement leur contribution dans la maı̂trise du procédé de précipitation, et notamment leurs avantages face aux réacteurs agités standards.
Expanded micro-particles by supercritical antisolvent precipitation: Interpretation of results
The Journal of Supercritical Fluids, 2008
Supercritical antisolvent (SAS) micronization has been used to obtain nanoparticles and micro-particles of several kinds of materials. Sometimes hollow expanded micro-particles have also been obtained. This work is focused on the analysis of this last morphology. We organized literature data and our previous experiments and we added new experiments on previously tested compounds and on compounds never tested before.
The Journal of Supercritical Fluids, 2008
Supercritical antisolvent micronization has been the subject of many works aimed at the production of precipitates with controlled particle size and morphology. Several morphologies have been observed; but, the production of spherical micrometric particles has been the major objective of most of the studies performed. Therefore, in this work, literature data analysis on spherical and related morphologies has been performed. The ranges of process conditions at which spherical microparticles have been obtained have been listed and discussed.
Journal of Supercritical Fluids, 2008
Ethanol is a commonly added modifier to supercritical CO 2 for particle formation from aqueous solutions. Four modifiers -methanol, ethanol, 2-propanol and acetone -were studied to determine the extent of the effect of the modifier selection on the particles produced and to determine more precisely the precipitation mechanisms. The strong anti-solvent effect of methanol on the solute was shown by the production of metastable -glycine, phenylalanine anhydrate and lysozyme agglomerated nanoparticles. Ethanol showed such an anti-solvent effect only when use at higher fraction in the supercritical phase, followed by 2-propanol and acetone. 2-Propanol and acetone mainly contributed to the precipitation of the solute by increasing the solubility of the water in the supercritical phase. In such precipitation conditions the more stable ␣-glycine, phenylalanine monohydrate and lysozyme microspheres were produced by the evaporation of the solution into the CO 2 phase.
Analysis of the mechanisms governing the supercritical antisolvent micronization
2003
Supercritical Antisolvent (SAS) precipitation is a semi-continuous precipitation technique developed to produce micrometric and sub-micrometric particles that are not attainable by conventional methods. Despite the fact that many works have been published on the generation of particles by SAS, only a limited number of them has been focused on the mechanisms controlling particle formation. In this work, a study of the precipitation process has been performed to understand the role of phase behavior in controlling morphology and dimension of the precipitates. The mixture Yttrium Acetate (YAc)/Dimethylsulfoxide (DMSO), using supercritical CO 2 as the antisolvent, has been chosen as the model system. The results showed that operating above the Mixture Critical Point (MCP) sub-micronic particles are generated nearly independently from the kind of the injector. We also demonstrated that it is also possible to obtain submicronic particles (with an average diameter of 0.28 µm) or macro-particles (up to 50 µm) by simply changing the operating pressure and/or temperature. These results have been explained on the basis of the position of the operating point with respect to the MCP of the pseudobinary mixture DMSO/CO 2. Particularly, we have seen that the single-phase region in the gasrich side of the pressure-composition solubility diagram and below the MCP can be usefully explored in order to modify the particle dimensions of the precipitate.
Nanoparticles production by supercritical antisolvent precipitation: A general interpretation
The Journal of Supercritical Fluids, 2007
Supercritical antisolvent micronization (SAS) has been used to obtain microparticles of several kind of materials, but the production of nanoparticles have been observed and studied in some cases only. This work is focused on the systematic production of nanoparticles using SAS. We performed experiments on several compounds and different solvents at selected operating conditions, obtaining nanoparticles with mean diameters ranging between 45 and 150 nm, thus demonstrating that nanoparticles production is a general characteristic of this process. Moreover, we found a correlation between nanoparticles mean diameter and the reduced concentration of the starting liquid solution that can allow the prediction of the mean diameter obtainable at fixed process conditions. Nanoparticles with mean diameters as small as 45 nm have been obtained, operating at 150 bar, 40 • C and x CO 2 = 0.97; but, even smaller nanoparticles can be obtained operating at higher pressures. The mechanism that produces nanoparticles in supercritical antisolvent precipitation has also been discussed.
Chemical Engineering Transactions, 2015
Precipitation processes such as SAS - Supercritical Antisolvent - based on supercritical fluids have been extensively used in the crystallization of a wide variety of materials in a controlled manner allowing one to obtain nanoscale particles which are almost spherical in shape. The understanding of the dynamics of the particles inside the precipitation chamber allows the decision for operating conditions that are favorable to the precipitation of particles of small size, but there is still a great experimental challenge. In this paper, a Euler- Lagrange approach with one-way coupling was proposed to evaluate the dynamics of particles in a chamber of SAS precipitation prescribing one distribution of particle diameters, assuming values within ranges specified from experimental values. From the software ANSYS CFX used to obtain the solution of the mathematical model, the following variables were analyzed: mixture velocity, the time of trajectory, the dead zones and the average diamete...
Chemical Engineering Journal, 2011
A general description of the mechanisms governing the supercritical (sc) antisolvent (SAS) process is given. It simplifies the complex interactions of phase equilibria, jet fluid dynamics and mass transfer by two characteristic and competing times. One of them characterizes the time for the disappearance of the interface between the liquid and the fluid phase (liquid/fluid interface) where the fluid phase is represented either by a liquid or by a sc fluid phase depending on the pressure and the mixture composition. The second one is the time for particle precipitation. This description is experimentally supported by the investigation of the SAS process at various process conditions using in situ light scattering measurements which allow the access to both, to the liquid/fluid (droplets) and to the solid/fluid (particles) interface. SAS experiments were conducted by injecting the solution -yttrium acetate dissolved in dimetylsulfoxide -into the antisolvent carbon dioxide with different flow rates at a constant carbon dioxide molar fraction. The variation of the liquid flow rate did not affect the morphology of the precipitate. As a consequence, the occurrence of nano particles, micro particles and expanded micro particles can be assigned to the precipitation of the particles from a single-phase mixture, a two-phase mixture of short lifetime and a two-phase mixture of long lifetime, respectively. These particular precipitation regimes have been experimentally attained by varying either the pressure or the solute concentration.