Terpenoids as solvents for the separation of 2,3-butanediol from water: Phase equilibria and process evaluation

2,3-butanediol (2,3-BDO) is a versatile platform chemical that can be produced via fermentation in aqueous solution. The energy intensive recovery of the high boiling 2,3-BDO from water via distillation hinders the economic viability of biotechnological produced 2,3-BDO. Hence, extraction-distillation processes using novel solvents from the class of terpenoids, namely menthol, thymol, and carvacrol, are proposed. To this end, binary and ternary liquid-liquid equilibrium (LLE) data for H₂O, 2,3-BDO, and each terpenoid, as well as boiling point data for 2,3-BDO and the respective terpenoid, are measured. The thermodynamic phase equilibria are correlated with the non-random two liquid (NRTL) model and consecutive process design of the extraction-distillation processes is conducted using Aspen Plus. Conventional solvents (isobutanol, 1-butanol, and oleylalcohol), thymol, and carvacrol are assessed in terms of specific exergy demand for the production of 2,3-BDO. The lowest specific exergy demands were found for oleyl alcohol (5.38 kJ g⁻¹) and thymol (5.14 kJ g⁻¹), carvacrol (5.49 kJ g⁻¹). Hence, terpenoids are a competitive class of solvents and should be included in solvent screening approaches.