Solvent selection for the recovery of acetic acid; Comparison of simulated and laboratory results for liquid-liquid extraction

Acetic acid is a well-known fermentation inhibitor for the conversion of biomass sugars to ethanol.  Liquid-liquid extraction was used to assess the ability of a solvent to extract acetic acid from a dilute aqueous solution prior to fermentation.  Thirty-two solvents were simulated in AspenPlus® to evaluate their ability to extract acetic acid from a dilute aqueous solution.  The solvents were selected based on their ability to extract the acetic acid at a lower solvent consumption rate while not extracting water from the raffinate.  In the next step the fate of the sugars in the aqueous solution was studied.  A desired extraction system allows the sugars to remain intact and to leave the extraction column with the aqueous stream.  A group of nine organic solvents were selected for laboratory experimentation based on the mentioned criteria.  The simulation outputs are not completely reliable without experimental results because the property method chosen for the simulation will result in unrealistic results.  It is necessary to experimentally verify which property method best suits the simulation.  Laboratory experiments were performed on a solution of acetic acid, water, glucose, and xylose mixed with varying levels of solvent.  This first set of experiments narrowed the list down to four possible solvent which were then assessed using a corn stover hydrolysate to confirm which scenario best fits the extraction.  The three property methods evaluated demonstrated that they were compatible with the laboratory experimental results for different solvents at the three examined loading rates.