Butanol recovery using ionic liquids as green solvents

BACKGROUND Consistent rising energy demand due to depleting conventional resources leads to the development of alternative energy sources. Biobutanol is a promising fuel because of its high energy content. However, the fermentative technique of butanol generation by the acetone−butanol−ethanol procedure utilizing solventogenic Clostridium has serious constraints. It represses microbial movement (ordinarily ≥10 g L−1) and influences its production. To extricate butanol from aging broth, there are different separation techniques. To conquer these issues, ionic liquids can be utilized as novel extractants replacing ordinary unstable solvents. RESULTS In the present paper, separation of butanol (simulated) from aqueous media utilizing typical hydrophobic ionic liquids – 1‐hexyl‐3‐methylimidazolium bis(trifluoromethanesulfonimide) (HMIM[NTF2]), 1‐hexyl‐3‐methylimidazolium hexafluorophosphate (HMIM[PF6]) and other solvents; oleyl alcohol (OA), tri‐n‐butyl phosphate (TBP) and their blends – has been carried at 298 ± 1 K. Results were compared with TBP, which was taken as a conventional reference solvent. Extraction efficiency was observed in the range TBP > 85–87% for OA > 55–85 for HMIM[NTF2] > 26–66% for HMIM[PF6], respectively. From the equilibrium experiments, distribution coefficients (Kd) values were observed in the range of TBP (7–23) > OA (5–7) > HMIM[NTF2] (1.2–5.6) > HMIM[PF6] (0.36–1.94), respectively. CONCLUSION The present study shows how extractant–diluent combinations can be used to obtain a non‐toxic extractant to tune characteristics of ionic liquids and improve fluid properties by significantly increasing distribution coefficients and extraction efficiencies. This could be helpful for separation of butanol from aqueous phase. © 2021 Society of Chemical Industry (SCI).