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Structure and Dynamics Study of 1-Ethyl-3-Methyl-Imidazolium for the Separation of CO2 from N2

Jacob Townsend
Department of Chemistry, University of Tennessee

This page shows the simulation of 1-ethyl-3-methyl-imidazolium hexafluorophosphate ionic liquid system with 10% mole fraction CO2 in the NPT ensemble.

Room temperature ionic liquids (RTILs) have the ability to separate gases such as CO2 and N2 through a solubility-diffusivity selective process. This is especially true when they are embedded in a supporting polymeric membrane. [1,2] The separation factor for gases through the liquid or membrane is given by a product of solubility and diffusivity. Molecular dynamics was used to study the self-diffusivity of the gases and ions in the ionic liquid solution.

The ionic liquid density was studied by running simulations on 216 ion pairs over a range of temperatures between 300-400K with the NPT ensemblen. After the system was equilibrated, data was collected for self-diffusivity parameters and radial distribution functions were generated. It was found that inclusion of gases into the liquid did not significantly change the structure of the liquid, as the density and ion mobility remain unchanged. It was found that CO2 has a lower diffusivity than N2. When analyzing the radial distribution function, it was found that CO2 remains closer to the anion than N2, which may contribute to the lower diffusivity of CO2.

Interactive Structures

Color Legend:

  • green = fluorine
  • blue = nitrogen
  • white = hydrogen
  • grey = carbon
  • red = oxygen


1. Hojniak, S. D.; Khan, A. L.; Holloczki, O.; Kirchner, B.; Vankelecom, I. F. J.; Dehaen, W.; Binnemans, K. J. Phys. Chem. B 2013, 117, 15131–15140.
2. Wang, J.; Wolf, R. M.; Caldwell, J. W.; Kollman, P. A.; Case, D. A. J. Comput. Chem. 2004, 25 (9), 1157-1174.

posted: April 2018.
updated: April 2018.