Bio-butanol recovery using non-fluorinated task-specific ionic liquids (TSILs)

Biobutanol has received major attention as an alternative for and additive to fossil fuels. Biobutanol produced via fermentation is hampered by low butanol concentrations in the fermentation broth. An efficient separation process is required to make biobutanol production economically viable. In this work, liquid–liquid extraction of butanol from water, employing nonfluorinated task-specific ionic liquids (TSILs) has been evaluated against distillation and extraction with conventional solvents. Experimental data for the equilibrium distribution ratios of butanol and water were used in a conceptual process design study to find the most promising solvent. The results show that the IL with the best distribution coefficient and very high selectivity was [TOAMNaph] (DBuOH = 21, S = 274), performing much better than the benchmark solvent oleyl alcohol (DBuOH = 3.42, S = 192). The conceptual design study showed that butanol extraction with [TOAMNaph] requires 73% less energy than in conventional distillation (5.65 MJ/kg BuOH vs 21.3 MJ/kg for distillation).