The thermo-kinetic inhibition mechanism of six imidazolium-based ionic liquids (ILs) on methane clathrate hydrate formation and growth is studied in this work using classical molecular dynamics (MD) simulation. The ionic liquids investigated include 1-(2,3-dihydroxypropyl)- 3-methylimidazoliumbis(fluorosulfonyl)imide ([C3(OH)2mim][f2N]), 1-(2-hydroxyethyl)-3-methylimidazolium bis(fluorosulfonyl)imide ([C2OHmim][f2N]), 1- ethyl-3-methylimidazolium tetrafluoroborate ([C2mim][BF4]), 1-butyl-3-methylimidazolium tetrafluoroborate ([C4mim] [BF4]), 1-butyl-3-methylimidazolium acetate ([C4mim][OAc]) and 1-ethyl-3-methylimidazolium ethylsulfate ([C2mim][EtSO4]). Simulations showed that [C2OHmim][f2N] and [C3(OH)2mim][f2N] are strongly hydrated compared to other ILs because of hydrogen bonding between OH groups of the cation and water molecules. They also exhibit high diffusion rates towards crystal surface and bond to it through strong intermolecular interactions. As a result, these two ILs are stronger thermo-kinetic inhibitors for formation and growth of methane hydrates compared to other ILs studied in this work as well as conventional inhibitors like methanol and NaCl. The simulations also revealed that cations of [C3(OH)2mim][f2N] and [C2OHmim][f2N] show that the presence of ions near the hydrate crystal causes hindrance for water and guest molecules adsorbing on the hydrate surface, which inhibits the growth of hydrate crystals. In addition, it is shown that [C3(OH)2mim][f2N] and [C2OHmim][f2N] are more likely to inhibit hydrate formation.
Methane hydrates, which could be considered as a source of energy , are commonly formed during natural gas production operations under certain temperature and pressure conditions. Formation of stable gas hydrates in gas and oil production and pipelines can lead to severe safety problems and huge economic loss . Therefore, several different methods have been developed in order to retard gas hydrate formation. Thus, hydrate inhibitors have achieved widespread popularity. There are two types of inhibitors, namely thermodynamic and kinetic inhibitors. Most of the free water is hydrogen bonded to the inhibitor molecules by injecting thermodynamic inhibitors. This reduces the water activity so that lower temperatures and higher pressures are required to form hydrates at low concentrations of nonhydrogen bonded water. Kinetic inhibitors bond to the hydrate surface and prevent plug formation for a period longer than the free water residence time in a pipeline. It has also been found that a combination of thermodynamic and kinetic inhibitors is still required to give better results in some cases.
Publisher : 2nd National Iranian Conference on Gas Hydrate (NICGH)
By : Mohammad Ebrahim Haji Nasrollaha , Bagher Abareshia, Cyrus Ghotbi ,Vahid Taghikhania , Amir Hossein Jalili
File Information: English Language/ 12 Page / size: 983 KB
سال : 1392
ناشر : دومین کنفرانس ملی هیدرات گاز (NICGH)
کاری از : محمد ابراهیم حاجی نصرالله، باقر ابراشیا، کوروش گرمبی، وحید تقیحیان، امیر حسین جلیلی
اطلاعات فایل : زبان انگلیسی / 12 صفحه / حجم : KB 983