Measurement of the phase behavior of the ternary system carbon dioxide + acetone + phenanthrene

Abstract

As a representative model system for the gas-anti-solvent (GAS) process, the phase behavior of the ternary system carbon dioxide + acetone + phenanthrene has been studied experimentally. Carbon dioxide was chosen as the gaseous anti-solvent, acetone was chosen as the organic solvent, and phenanthrene was chosen as the model solute. In each experiment, a solution of phenanthrene in acetone was expanded using carbon dioxide as the anti-solvent. A synthetic method was used for the measurements of the various phase boundaries. Three-phase equilibrium data solid (phenanthrene)-liquid-vapor were obtained from intersection of two-phase isopleths vapor-liquid and solid-liquid. For a variety of compositions, results are reported for this ternary system within temperature and pressure ranges of (295 to 350) K and (1.0 to12.5) MPa, respectively. As was established in a previous study on the system carbon dioxide + 2-propanol + salicylic acid, it turned out that also in the system carbon dioxide + acetone + phenanthrene the carbon dioxide concentration significantly affects the optimum operational conditions of the GAS process (i.e., at lower concentrations carbon dioxide acts as a co-solvent, while at higher concentrations it acts as an anti-solvent). Also, it is shown that at a certain temperature, it is possible to precipitate most of the dissolved solute within only a small pressure window.