Extraction of ethanol with higher carboxylic acid solvents and their toxicity to yeast

In a screening exercise for ethanol-selective extraction solvents, partitioning of ethanol and water from a 5 wt% aqueous solution into several C8–C18 carboxylic acids was studied. Results for the acids are compared with those from alcohols of similar structure. In all cases studied, the acids exhibited higher separation factor, but lower capacity than their alcohol analogs. Solvent toxicity to a commercial yeast commonly used in fuel ethanol production was evaluated for selected solvents. For the acids studied, those containing 12 or fewer carbons were toxic or inhibitory to the yeast; those containing 16 or more carbons were non-toxic and non-inhibitory.