The phase behavior and micro-structure of the supercritical CO2 (scCO(2)) microemulsion system with nonionic 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 scCO(2) 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 scCO(2) 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 scCO(2) 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 scCO(2) microemulsion system. This work might provide reference to the purification of polyols in fermentation broth and help to understand. the microstructure and solubilization property of polar compounds in scCO(2) microemulsion system. (C) 2015 Elsevier B.V. All rights reserved.