Salting-out extraction of acetoin from fermentation broths using hydroxylammonium ionic liquids as extractants

Abstract

The salting-out extraction (SOE) systems based on ionic liquids (ILs) have attracted extensive attention in the separation of bio-based products, in which imidazolium ILs were widely studied. However, the high cost and toxicity have hindered their further industrial application. Hydroxylammonium ILs have the characteristics of cheap raw material, simple synthesis process and low toxicity, but are rarely used in the SOE systems. In this work, five hydroxylammonium ILs (2 cations and 4 carboxylate anions) were synthesized and used in SOE of bio-chemicals. The phase forming abilities of ILs with K3PO4 and H2O were affected by the hydrophilicity of anions and cations. With the increase of carbon chain length, phase forming abilities of ILs increased, while the temperature had little influence. The partition behaviors of acetoin, ILs and 2,3-butandiol, and the selectivity of acetoin to organic acids were investigated and compared at different concentrations of ethanolammonium butyrate (EOAB) and K3PO4. In a SOE system consisted of 6% EOAB-38% K3PO4 (w/w), the recovery of acetoin, IL and 2,3-butandiol was 92.7%, 76.0% and 86.0%, respectively, and the selectivity of acetoin to lactic acid and acetic acid was 16.46 and 3.85, respectively. The ATR-IR spectra showed the hydrogen bonds formed between acetoin and O-H, N-H, –COO– of hydroxylammonium IL played an important role in the efficient extraction of acetoin from fermentation broths.