Re-evaluating 2-heptanol as solvent for the extraction of 2,3-butanediol from water

The performance of an extraction-distillation process for separating 2,3-butanediol from H₂O was evaluated in a recent study, finding high efficeincy when using 2-heptanol as solvent for extraction. Since the study was based on liquid-liquid equilibrium (LLE) data mainly derived from molecular simulations, the aim of this communication was to consolidate the database by providing experimental phase equilibrium data and to re-evaluate 2-heptanol as solvent. Based on LLE experiments, a solvent-to-feed ratio (S/F) of 3.175 was required to recover 95 % of 2,3-BDO in a counter-current extraction column. This S/F is 21.9 times higher than the estimation derived from the data based on molecular simulations. The high S/F results in a strong dilution of 2,3-BDO in the extract. Experimental investigation of the boiling point data of the 2,3-BDO – 2-heptanol system for subsequent distillation revealed the presence of a temperature minimum azeotrope at low 2,3-BDO concentrations, which limits the feasibility of the overall process. Since the use of 2-heptanol as solvent is oftentimes referred to in the community of diol separation, the results presented in the work at hand are relevant to a broad readership.