Anhydrous ethanol membrane processes

Hyperfiltration (reverse osmosis), pervaporation, and gas/vapor permeation have been proposed for producing anhydrous ethanol. Several companies such as GFT Membrane Systems GmbH, Kalsep, and Lurgi have constructed membrane separation plants which utilize the pervaporation process or the vapor permeation process where flat membranes are used. 

Removal of water from organic mixtures by pervaporation or vapor permeation is now a widely accepted state-of-the-art technology. Meanwhile, new membranes have been developed that allow separating simple alcohols like methanol or ethanol from their mixtures with organic solvents whereby these mixtures are virtually anhydrous. The first industrial plant of this kind started its operation in 1997 [16], separating methanol out of its azeotropic mixture with TMB (trimethylborate). Many commonly used organic solvents form azeotropes with methanol that cannot always easily be separated. The respective simple esters of methanol and ethanol also form azeotropes with the alcohol, and the often-used water wash for spHtting of the azeotrope may lead to unwanted hydrolysis. It can be assumed that the number of applications of pervaporation processes will increase in the future for this type of separation. 

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