PROCESS FOR PURIFYING AQUEOUS CRUDE ETHANOL SOLUTION.

摘要

A purification process for efficiently removing lipophilic impurities contained in an aqueous crude ethanol solution, in particular, C3 and C4 alcohols, which comprises: (a) the first extraction step wherein an aqueous crude ethanol solution is treated with a pressurized extractant comprising carbon dioxide in a liquidized or supercritical state to thereby remove lipophilic impurities, except for C3 and C4 alcohols, contained in the crude ethanol by extraction with the extractant, (b) the concentration/distillation step wherein a raffinate obtained in the first extraction step is fed to a distilling column to thereby obtain a highly concentrated aqueous ethanol solution from the column top and draw a fraction containing C3 and C4 alcohols from the column as a side stream, (c) the second extraction step wherein the side stream is brought into contact with the pressurized extract obtained in the first extraction step to thereby extract the C3 and C4 alcohols contained in the side stream with the extract, and (d) the water washing step wherein the pressurized extract obtained in the second extraction step is brought into countercurrent contact with water in a pressurized state under such a condition that the weight ratio of the water to the extract is 0.3 or less to thereby recover the alcohols contained in the extract into an aqueous phase.