265469 Dynamics Study and Gas Solubility in Phase Change Ionic Liquid for CO2 Capture
Phase change ionic liquids (PCIL) undergo a solid to liquid phase transition when they react with CO2. The heat of fusion during the phase change can be utilized to reduce the energy requirements for CO2 capture. Here we present the results of a molecular simulation study in which the water solubility, dynamics and liquid structure of PCILs are computed and used to gain an understanding of these liquids.
Water solubility in PCILs is important because in the regeneration step, the separation of water from the IL solution requires additional thermal energy to vaporize the water. Water solubility is determined in molecular simulation by calculating the solvation free energy. These are related to the Henry's Law constants, which are then compared with experimental data. The enthalpy and entropy of solvation are also obtained from the simulations. A hydrogen bond analysis is performed and the structure of the liquid is studied in an effort to explain the solubility calculations. A trend of hydrophobicity in a series of PCILs is predicted.
It has also been found that the viscosity of aprotic heterocyclic anion-based PCILs does not increase due to CO2 complexation, unlike conventional amines. Molecular dynamics simulations are performed to investigate the relationship between dynamic properties and liquid structure of PCILs. In this work, a prediction is made on dynamics and by analogy the viscosity of these ionic liquids by simulation and experiments. It is found that, like the experimental results, the dynamics are unaffected by reaction with CO2 when aprotic heterocyclic anion-based PCILs are used.