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Experimental Determination & Thermodynamic Modeling of Solubility of Gases in Ionic Liquids

Rahmati Rostami, Mahboubeh | 2009

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 39629 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Ghotbi, Cyrus; Behzadi, Bahman; Jalili, Amir Hossein; Ahmadi, Amir Naser
  7. Abstract:
  8. Ionic liquids (IL's) are found to be potentially suitable solvents for the chemical process industry, especially due to their negligible vapor pressure which can result in a major decrease of solvent loss and the environmental harm. One of the foreseeable industrial applications in the field of natural gas processing is the replacement of traditional organic solvents (usually alkanol amines) presently used for the absorption of H2S from sour gases, by suitable IL's. Ionic liquids have been proposed for the separation of gas mixtures. In particular, ionic liquids have been suggested for the removal of the acid gases, hydrogen sulfide, and carbon dioxide, from natural gases and refinery gases. In this work, Solubilities of hydrogen sulfide have been measured experimentally in six different solvents including room-temperature ionic liquids [bmim][PF6], 1-butyl-3-methyilimidazolium hexafluorophosphate ([bmim][BF4]), 1-butyl-3-methyilimidazolium tetrafluoroborate ([bmim][Tf2N]), 1-butyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide
    ([hmim][Tf2N]), 1-hexyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide ([hmim][BF4]), 1-hexyl-3-methylimidazolium tetrafluoroborate ([hmim][PF6]) 1-hexyl-3-methylimidazolium hexafluoro phosphate at temperatures ranging from 303 to 343 K and for pressures ranging from 0 to 1 Mpa. Based on the measured solubility data, values of Henry’s constants, enthalpies, entropies and Gibbs free energies of solution and also partial molar volumes of H2S at infinite dilution have been determined for the different systems and conditions. The measured solubility data have then been modeled using the SAFT-VR approach, by incorporating the square-well potential for short-range interactions and an additional term to account for polar interactions between solvent-solvent and solvent-solute molecules, especially resulting from the permanent charges on the chain molecules of the solvents. The results show an average deviation of less than 4% in the calculation of system pressure and density. Experimental measurement and thermodynamic modeling of the solubility and other relevant thermodynamic properties for the systems containing hydrogen sulfide and different IL's at different conditions is thus a prerequisite for correct process design, economic process evaluation and finally suitable industrial application of the relevant systems. Comparison showed that the solubility of H2S in these sex ionic liquids was in sequence: [hmim][BF4]>[bmim][NTF2]>[bmim][BF4]>[hmim][NTF2]> [hmim][PF6]> [bmim][PF6
  9. Keywords:
  10. Statistical Assosiating Fluids Theory (SAFT) ; Ionic Liquids ; Hydrogen Sulfide ; Square-Well Potential Model

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