Quaternary solubility of acetic acid, diacetin and triacetin in supercritical carbon dioxide

- Acetic acid has the highest solubility in scCO2.
- The presence of diacetin and triacetin decreases the solubility of acetic acid in the mixture.
- The hydrogen-bond forming affect the solubility in scCO2.
- Selective extraction of acetic acid is feasible using scCO2.

By a continuous-flow apparatus, quaternary solubility of acetic acid, diacetin, and triacetin in supercritical CO2 was measured at constant flow rate of 180 mL min−1 and temperatures of 313 K, 333 K and 348 K in a pressure range of 70-180 bar. Acetic acid had the highest solubility in scCO2. The binary solubility of acetic acid was also investigated at temperature of 333 k in the pressure range of 70-180 bar. With going from binary to quaternary, acetic acid solubility decreased in the range of 85-90% at different pressures. The quaternary solubility of acetic acid was decreased in the presence of diacetin and triacetin, due to more effective hydrogen bonds with acetic acid and supercritical CO2. In addition, it was observed that the solubility of polar diacetin molecules in non-polar CO2 solvent increased by increasing temperature.

The selectivity of acetic acid extraction versus pressure from the mixture of acetic acid, DA and TA with scCO2 at different temperatures.102