ARS | Publication request: Solvent extraction of ethanol from aqueous solutions. 1. Screening methodology for solvents

Submitted to: Industrial and Engineering Chemistry Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 23, 2005
Publication Date: July 1, 2005
Citation: Offeman, R.D., Stephenson, S.K., Robertson, G.H., Orts, W.J. 2005. Solvent extraction of ethanol from aqueous solutions. 1. Screening methodology for solvents. Industrial and Engineering Chemistry Research. 44: 6789-6796.

Interpretive Summary: Currently the energy required to distill a gallon of ethanol from a fermentor and dehydrate it is equivalent to 18-22% of the fuel value of a gallon of ethanol. Solvent extraction is a less energy-intensive alternative to distillation. This paper is the first 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 develops a general screening method to evaluate solvents, investigates potential sources of error, and compares results to those in the literature. Improvements in extraction solvents could lead to reduction in energy required to produce ethanol from grain and biomass sources.

Technical Abstract: The evaluation of the potential for separation of aqueous ethanol mixtures by liquid-liquid solvent extraction has been complicated by inconsistent results and differing experimental methodologies between researchers developing distribution coefficient data. A screening method for measuring equilibrium distribution coefficients for solvent extraction of ethanol from dilute aqueous solutions is presented to minimize potential sources of variation. These include entrainment, incomplete equilibration, impurities, and temperature changes during preparation of samples for analysis. Multiple literature sources of data exist for each of ten solvents. Results for these ten solvents are compared between sources and to results generated from this method. The method also has general utility for the screening of solvents for extraction of other useful fermentation products.