A water-immiscible solvent/co-solvent mixture which extracts acetic acid from aqueous streams comprises(a) a water-immiscible solvent comprising greater than 50% by volume of a mixture of isomers of highly branched di-alkyl amines and less than about 1% by volume of mono-alkyl amines, said solvent having a coefficient of distribution greater than 10; and(b) at least 10% by volume of a non-alcoholic co-solvent having a boiling point lower than the boiling point of said solvent (a). Preferred water-immiscible solvent useful in the extraction of acetic acid from aqueous streams comprises about 91% by volume of a mixture of isomers of highly branched di-alkyl amines, about 0.2% by volume of mono-alkyl amines, and about 9% by volume tri-alkyl amines said solvent having a coefficient of distribution of greater than 10. An anaerobic microbial fermentation process for the production of acetic acid comprises the steps of:(a) fermenting in a bioreactor a gas stream comprising a least one gas selected from (1) carbon monoxide, (2) carbon dioxide and hydrogen, (3) carbon monoxide, carbon dioxide and hydrogen and (4) carbon monoxide and hydrogen in the presence of an aqueous stream comprising an anaerobic acetogenic bacteria in a nutrient medium, thereby producing a fermentation broth comprising acetic acid;(b) separating said bacteria from other components in said broth to provide a substantially cell-free stream;(c) continuously extracting acetic acid from said cell-free stream into a solvent phase by contacting said cell-free stream with a water-immiscible solvent/co-solvent mixture of the invention;(d) recycling said aqueous phase to said bioreactor and passing said solvent phase to a distillation column; and(e) continuously distilling from the product of (d) the acetic acid separately from the solvent phase under a temperature not exceeding 160°C; said extracting and distilling steps occurring without substantially degrading said amine to an amide, thus enhancing the efficiency of production of acetic acid.展开▼
