SOLUBILITY OF VEGETABLE CUTICULAR WAXES IN SUPERCRITICAL CO2 ISOTHERMAL CALORIMETRY INVESTIGATIONS

Vegetable cuticular waxes have to be separated from the more valuable essential oils in extraction processes carried out with supercritical fluids (namely CO2), allowing a solvent selectivity by modification of temperature and pressure. The solubility of these waxes in supercritical CO2 can be adequately represented by that of solid n-octacosane. The present work shows that isothermal investigations, carried out with a differential flux calorimeter with adequate cells, allow the solubility and solubilization enthalpy of n-octacosane to be determined. The results concern investigations either at constant pressure and variable supercritical CO2 flow-rate, or at zero flow-rate and increasing pressure. The latter conditions allow the solubility-pressure trend to be obtained, in satisfactory agreement with literature data derived from standard dynamic methods.