Separation of 1,3-propanediol using supercritical CO2 microemulsion with non-ionic surfactant Ls-54: Experiment and simulation

The phase behavior and micro-structure of the supercritical CO2 (scCO2) microemulsion system with non-ionic dodecyl (poly(ethylene-methylethylene glycol)) ether Ls-54 as surfactant are investigated in this study. A synergistic experimental and simulation study highlights the separation of 1,3-propanediol (1,3-PDO) from dilute aqueous solution in fermentation broth using this scCO2 microemulsion system. Phase behavior measurement and all-atom molecular dynamic simulation are carried out on the Ls-54/CO2/H2O ternary system and Ls-54/CO2/H2O/1,3-PDO quaternary system to study the solubilization property of 1,3-PDO. The results not only indicate the formation of the thermodynamic stable microemulsion system, but also demonstrate that 1,3-PDO can be selectively solubilized from dilute aqueous solution using the scCO2 microemulsion system with Ls-54 as surfactant by easily controlling the operating pressure. Moreover, the simulation results reveal that the microemulsion formation depends on the interaction between the water cluster and head groups of surfactant. Therefore, a new formation mechanism of the scCO2 microemulsion system with non-ionic surfactant is proposed. In addition, the size of microemulsion droplets in Ls-54/CO2/H2O/ethanol(EtOH) and Ls-54/CO2/H2O/1,3-PDO/EtOH system with ethanol as co-solvent are obtained using the method of small-angle X-ray scattering (SAXS) experiment, which also confirms the solubilization of 1,3-PDO in scCO2 microemulsion system. This work might provide reference to the purification of polyols in fermentation broth and help to understand the micro-structure and solubilization property of polar compounds in scCO2 microemulsion system.