A STUDY OF MASS-TRANSFER IN THE EXTRACTION OF IMPURITIES FROM ETHANOL AQUEOUS-SOLUTION BY CARBON-DIOXIDE AS A SOLVENT

Trace amounts of acetaldehyde, ethyl acetate, isoamyl alcohol, n-propanol and methyl ethyl ketone were effectively extracted and removed from the ethanol aqueous solution by carbon dioxide as solvent with countercurrent contractors. The experiments were carried out at 298.2 K and 7.0 MPa or 303.2 K and 7.5 MPa with solvent-to-feed ratios from 1.3 to 5.0 mol/mol. The concentration of feed ethanol aqueous solution was 20 mol%. Packed columns with 6 mm Raschig rings were employed as contractors. Although a certain amount of ethanol was dissolved into the solvent simultaneously with the trace components, the dissolved ethanol was easily recovered by scrubbing the solvent with a small amount of water. Assuming the state of infinite dilution for each component, a simple calculational procedure was devised to determine the height per mass-transfer unit for some components in packed columns from the experimental data.