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Molecular Simulation of Methane Hydrate Formation Investigation of [Emim][BF4] Ionic Liquid effects on Growth and Dissociation of Methane Hydrate Crystal Using Molecular Dynamics Simulation

Abareshi, Bagher | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 41676 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Ghotbi , Cyrus; Taghikhani, Vahid; Jalili, Amir Hossein
  7. Abstract:
  8. Formation of gas hydrates is a challenge in the oil and gas industry. Gas hydrate formation can be prevented by several methods. One of these methods is to utilize of inhibitor components. The gas hydrate inhibitors can affect hydrate formation from two aspects, i.e., thermodynamic or kinetic. In this work, thermodynamic and kinetic effects of [Emim][BF4] ionic liquid on growth and dissociation of methane hydrate crystal were investigated using molecular dynamics simulation. Molecular dynamics simulation is powerful tool to investigate the thermophysical, structural, and dynamic properties of methane hydrate and the formation, dissociation, and inhibition mechanisms at the molecular scale. In order to understand effect of [Emim][BF4] exactly, the influence of this ionic liquid was compared with effect of sodium chloride salt (NaCl) on hydrate crystal. NaCl is a well-known thermodynamic inhibitor and its inhibition mechanism has been explained clearly. The simulation box included two phase: solid methane hydrate crystal and liquid water. There were ionic liquid molecules or NaCl molecules in liquid water phase. The simulations were carried out at different temperatures for 1 nanosecond. The ionic liquids dissociate into cations and anions in water. The results of simulation showed the ions of ionic liquid are weakly hydrated compared with ions of NaCl. Therefore, thermodynamic inhibition of [Emim][BF4] is negligible. The simulations showed ions of ionic liquid, especially [Emim]+ cations, close to surface of hydrate crystal because of strong interactions between hydrate crystal molecules and ions of ionic liquid. The presence of solvated ions near a hydrate crystal causes a hindrance for the water and guest molecules adsorbing on a hydrate surface which inhibit the growth of hydrate crystal. In this way, ionic liquid acts as a kinetic inhibitor of methane hydrate. The results of simulations were agree with results of experimental reported for [Emim][BF4] ionic liquid
  9. Keywords:
  10. Molecular Dynamic Simulation ; Ionic Liquids ; Methane Hydrate ; [Emim][BF4]Sonic Liquid

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