Method for the separation of impurities from crude ethanol aqueous solution

Abstract

The present invention is a method for the separation of impurities from a crude ethanol aqueous solution, comprising of; (i) extracting lipophilic impurities within the crude ethanol aqueous solution into an extracting solvent phase by treating the crude ethanol aqueous solution with an extracting solvent comprising carbon dioxide in a liquid state or carbon dioxide in a super-critical state under conditions wherein a ratio of the weight of the extracting solvent to the weight of the crude ethanol aqueous solution is 2 or higher; and (ii) recovering ethanol entrained with the extracting solvent or ethanol and methanol entrained with the extracting solvent into an aqueous phase by contacting the extracting solvent phase resulting after extracting the impurities to with water in a countercurrent manner under pressures in a ratio of the weight of water to the weight of the extracting solvent of 0.3 or lower. In this method for separation, the extracting solvent ratio by weight in the step of extracting impurities is preferably 6 or higher when the crude ethanol is fermented ethanol and the extracting solvent ratio by weight therein is preferably 3 or higher when the crude ethanol is synthesized ethanol. The aqueous phase obtained in the step (ii) of washing with water is recirculated to the step (i) of extracting impurities. The method according to the present invention can yield a highly pure ethanol aqueous solution with high efficiency.

Dependencies are inferred from the claim text.