MODELING OF PARTICLE FORMATION IN SUPERCRITICAL ANTI-SOLVENT PROCESSES: DILUTED AND CONCENTRATED REGIME

摘要

In this work, a theoretical investigation on particle formation taking into account mass transfer and thermodynamic for ternary systems solvent-antisolvent-solute, and solute precipitation kinetic is presented for both diluted and concentrated polymeric solutions. A mathematical model of mass transfer between a droplet of polymeric organic solution and a compressed anti-solvent is solved for fully miscible conditions. The generalized Maxwell-Stefan diffusion equation is used. To fairly describe the thermodynamic of chain-like solutes, such as polymers, both the volumetric and equilibrium properties are represented by the perturbed-hard-sphere-chain-theory equation of state. For concentrated solution, where only one polymeric solid particle is generated from the initial organic-solution droplet, a simple solute precipitation kinetic gives radial profiles of solute and solvent composition, and precipitated solute as a function of time. Depending on the process variables, the solute precipitation can occur either at the initial droplet surface or internally leading either to a hollow sphere or to a compact particle, respectively. The simulation presented in this work provides the precipitated solute distribution as a function of radial coordinate and time. Process operative variables and mass transfer pathways could strongly affect the overall final particle morphology. Results are presented for solutes with different solubility and kinetic parameters.