Patent ID: 8002953

Claim:
An improved extractive distillation (ED) process for dehydrating an aqueous feedstock containing ethanol and water that comprises the steps of: (a) introducing an aqueous feedstock comprising ethanol and water into a middle portion of an extractive distillation column (EDC); (b) introducing a high-boiling water selective solvent into an upper portion of the EDC to contact the aqueous feedstock under extractive distillation conditions to produce a liquid bottoms stream that comprises water and high-boiling water selective solvent and to produce a vaporous overhead stream that comprises greater than 99.5 weight percent ethanol, wherein the EDC is operated with a liquid reflux-to-distillate ratio of less than about 0.5; (c) withdrawing at least a portion of the vaporous overhead from the EDC as a purified ethanol product; (d) feeding at least a portion of the liquid bottoms stream of the EDC into a solvent recovery column (SRC) to remove water therefrom and to yield a lean high-boiling water selective solvent stream wherein step (a) comprises forming a liquid bottoms stream comprising water, ethanol, and high-boiling water selective solvent and in step (d) the SRC produces an overhead stream comprising water and ethanol that is condensed to form a condensate that is fed into a distillation column to yield a liquid bottoms stream consisting essentially of water and an overhead stream comprising ethanol and water which is recycled to the EDC; and (e) recycling at least a portion of the lean high-boiling water selective solvent stream into the upper portion of the EDC.