(123b) Investigation of the Solubility of Carbon Dioxide in Complex Solvents by Experiment and Molecular Simulation
Formerly, the development of solvents for a certain separation task was a tedious issue, including the synthesis of the new compounds as well as their experimental investigation. Improved descriptions of molecular interactions enable us to estimate the properties of process solvents based on their molecular structure. Consequently, molecular simulations can be applied as a tool to rationalize the search for new process solvents.
Dendritic and hyperbranched polymers (HBPs) are currently being considered as solvents or entrainers within the field of thermal separations [1,2]. Hyperbranched polymers exhibit a high thermal stability as well as low melt viscosity. Furthermore, they have a negligible vapor pressure and their physical properties, such as solubility, selectivity and glass transition temperature can be tailored via the large number of functional and core groups [3,4]. Within this work, a structured approach is shown to evaluate the applicability of HBPs as process solvents for the removal of CO2 from gas streams. Canonical ensemble molecular simulations based on the TraPPE force fields  combined with the Widom test particle insertion method was used to compute Henry's law constants of CO2 in different model compounds. The method is verified by comparison with literature data and experimentally determined vapor liquid equilibria of hyperbranched polyglycerol + co-solvent + CO2 . Subsequently, this combination of Molecular Dynamics simulations and particle insertion is used to analyze the influence of combinations of ether- and alcohol-groups on the solubility of CO2. Furthermore, the impact of branched versus linear structures as well as the number of functional groups per molecule is shown.
 M. Seiler, Fluid Phase Equilib. 241 (2006) 155-174.
 J. Rolker et al. , Ind. Eng. Chem. Res. 46 (2007) 6572-6583.
 B. Voit, J. Polym. Sci. A : Polym. Chem. 38 (2000) 2505-2525.
 C.R. Yates et al., Eur. Polym. J. 40 (2004) 1257-1281.
 J.M. Stubbs et al., J. Phys. Chem. B 108 (2004) 17596-17605.
 M. Kozlowska et al., Proceedings of ECCE-6 2 (2007)