TERNARY SOLUBILITY OF BUTANOL STRUCTURAL ISOMERS IN SUPERCRITICAL CARBON DIOXIDE: INTERNAL HYDROGEN BONDING AND SELECTIVITY

摘要

Ternary solubility of 1-butanol/2-butanol, i-butanol/2-butanol, and i-butanol/t-butanol in supercritical carbon dioxide (SC-CO_2) have been measured, using a continuous flow apparatus, at a temperature and a pressure range of (40-60)°C and (80-140) bar respectively and at a flow rate of 140±5 mL/min. The ternary solubilities of the pairs were increased with pressure at constant temperature and they were reduced with temperature at constant pressure of 100 bar. Despite their different binary solubility in SC-CO_2 at pressure of 100 bar [1], their ternary solubility in SC-CO_2 were similar for the pairs of the structural isomers. The selectivity of SC-CO_2 for each pair of isomers were reported. The observed solubility of alcohols in SC-CO_2 were affected by intermolecular hydrogen bonding. FT-IR spectra of neat and mixed liquid solutes were used to explain the effect of the intermolecular hydrogen bonding on the solubility of butanol structural isomers. The ternary solubilities of the butanol structural isomers were also compared with their binary solubilities and several conclusions were made regarding the structure-solubility relationship. The ternary solubilities of the butanol structural isomers were also measured at the different solute molar ratio of 0.33, 0.50, 1.0, and 2.0 in the equilibrium cell at 50°C and 100 bar. The results show that the solubilities of each solute are depended on their molar ratio in the equilibrium cell. But, the total solubilities remain constant, indicating that the saturation condition has been established.