PROCESS FOR SEPARATING IMPURITIES FROM AQUEOUS SOLUTION OF CRUDE ETHANOL.

摘要

A process for separating impurities from an aqueous solution of crude ethanol, which comprises an impurity extraction stage (i) wherein an aqueous solution of crude ethanol is treated with an extractant comprising carbon dioxide in a liquid or supercritical state under such a condition that the weight ratio of the extractant to the aqueous solution is at least 2 to thereby extract lipophilic impurities present in the crude ethanol into the extractant phase, and a water washing stage (ii) wherein the extractant which has passed through the stage (i) is brought into countercurrent contact with water under pressure under such a condition that the weight ratio of the water to the extractant is 0.3 or less to thereby recover ethanol, alone or together with methanol, entrained with the extractant in the water phase. It is preferable in this process that the weight ratio of the extractant to the aqueous solution be at least 6 or at least 3, respectively, when the crude ethanol is fermentation ethanol or synthetic ethanol, and it is also possible to recirculate the water phase obtained in stage (ii) into stage (i). This process provides a highly pure aqueous solution of ethanol efficiently.