ARS | Publication request: Extraction of ethanol with higher alcohol solvents and their toxicity to yeast

Submitted to: Separation and Purification Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 5, 2008
Publication Date: June 13, 2008
Citation: Offeman, R.D., Stephenson, S.K., Franquivillanueva, D.M., Cline, J.L., Robertson, G.H., Orts, W.J. 2008. Extraction of ethanol with higher alcohol solvents and their toxicity to yeast. Separation and Purification Technology. 63: 444-451.

Interpretive Summary: Currently the energy required to distill a gallon of ethanol from a fermentor and dehydrate it is equivalent to 18-22% of its total fuel value. Solvent extraction is a less energy-intensive alternative to distillation. This paper is the fourth in a series that searches for better solvents for recovering ethanol from aqueous solutions, and seeks to develop a better understanding of solvent molecular properties that enhance extraction. This paper presents new data for C16 – C20 alcohol solvents, and develops empirical power-law expressions to model data for 57 alcohol solvents. Improvements in extraction solvents could lead to reduction in energy required to produce ethanol from grain and biomass sources.

Technical Abstract: In a solvent extraction screening study, several beta-branched alcohols in the 16 20 carbons range show improved extractive performance to recover ethanol from aqueous solutions compared to commonly studied solvents such as oleyl alcohol and 1-dodecanol. These beta-branched alcohols were selected based on extrapolation of results in earlier work with lower molecular weight aliphatic alcohol solvents, that indicated higher separation factors should be realized when hydroxyl position is mid-chain, and there is branching. Solvent toxicity to a commercial yeast commonly used in fuel ethanol production also was evaluated for these as well as several lower molecular weight alcohols. For the alcohols studied, those containing 12 or fewer carbons were toxic or inhibitory to the yeast; those containing 16 or more carbons were nontoxic and non-inhibitory.