Precipitation of methionine and ethyl cellulose in carbon dioxide + ethanol + acetic acid systems at high pressures: Phase equilibrium data for the GAS antisolvent process

Abstract

This work reports experimental data on the phase transitions in the quaternary system involving carbon dioxide, ethanol, acetic acid and solute (methionine or ethyl cellulose) at high pressures. Experimental data were obtained by the synthetic method, with a variable volume visualization cell, in the temperature range of 308.15–328.15 K and pressures from 6.19 to 11.15 MPa. For the quaternary systems, the solutes were previously solubilized at two different concentrations, 0.1 mg/mL [0.0110% mass fraction] and 0.2 mg/mL [0.0221% mass fraction] for methionine and 2.5 mg/mL [0.2757% mass fraction] and 5.0 mg/mL [0.5514% mass fraction] for ethyl cellulose, in a 1:1 mass ratio solution of ethanol to acetic acid. Vapor-liquid-type phase transitions were observed, characterized as bubbles in the presence or absence of solid phase. A solid phase was observed for all solute concentrations evaluated in this study. Determination of the region of precipitation of methionine or ethyl cellulose is important to identify the optimal concentration of the solvent/solute mixture, where CO2 will act strongly as an antisolvent, ensuring a high efficiency of the GAS technique. Thermodynamic modeling presented satisfactory results, where it adequately described of experimental phase equilibrium data, neglecting the acetic acid dimerization effect.