Ethanol separation by adsorption‐desorption

Abstract

One of the major problems associated with the production of ethanol by fermentation is the high energy expenditure for the separation of ethanol from the fermentation broth. Using present distillation methods, energy requirements range from 4.4 to 9.1 MJ/L of 95% (v/v) ethanol, depending on the incoming ethanol concentration. The additional energy needed to break the azeotrope amounts to 2.6 MJ/L of ethanol. The total process of ethanol separation accounts for more than 50% of the energy required for ethanol production. Even though, in terms of the degree of separation, conventional distillation is very effective, new techniques for the separation of ethanol are being developed to further bring down energy costs. Some of these methods are vapor recompression, multicolumn vacuum distillation, estraction with liquid CO/sub 2/, preferential adsorption of water, selective sorption of ethanol, etc. These approaches have gained prominence because of their lower energy consumption (2-4 MJ/L) compared to the 7-11 MJ/L called for by conventional distillation. Selective sorption of ethanol from fermented mash by solid sorbents (with a higher selectivity of ethanol than water), followed by stripping of the sorbed ethanol, may totally eliminate the distillation process and represents a promising low-energy approach to ethanol separation. In thismore » communication, the preliminary results on an adsorption-desorption system which uses resins with polystyrene or acrylic bases and activated carbons will be discussed. (Refs. 10).« less