(200b) Feasibility Studies on Dehydration of Ethanol by Distillation Using Salt Effect (on VLE)

Ethanol makes an azeotropic mixture with water. Consequently, ordinary distillation processes are unable to purify ethanol. But dissolving salts into the ethanol-water mixture changes the vapor-liquid equilibrium; some salts are able to break the azeotrope. Making use of this salt effect, the azeotropic mixture can be separated into ethanol and water.

We studied the feasibility of dehydrating aqueous ethanol by utilizing the salt effect. For this we found that calcium chloride is the most effective salt. From aqueous solutions of 50 to 75%, simple distillation using the salt effect can recover 93 to 96% of the ethanol. Salt in the ethanol-water mixture must be present at saturation level. After distillation of the ethanol, the salt solution should be further distilled, to remove the water in the still in preparation for the next treatment. Depending on the initial water content, the ethanol recovery is from 88% to 99.9%.