Solubility of Syringic and Vanillic Acids in Supercritical Carbon Dioxide

Abstract

The solubility in supercritical carbon dioxide, at pressures from (10 to 50) MPa and temperatures from (40 to 60) °C, is reported for two nonflavonoid, low molecular weight phenolic compounds, 4-hydroxy-3,5-dimethoxybenzoic acid (syringic acid) and 4-hydroxy-3-methoxybenzoic acid (vanillic acid). Two types of models have been used for correlation of the experimental solubility data. First a rigorous thermodynamic method, with the Peng−Robinson equation of state, was used to determine the fugacity of the fluid phase. Second, two semiempirical density-dependent correlations were used: a linear correlation between the enhancement factor and the density of the solvent, as suggested by Schmitt and Reid, and the Chrastil correlation.