Tuning ionic liquids for hydrate inhibition

Abstract

Pyrrolidinium cation-based ionic liquids were synthesized, and their inhibition effects on methane hydrate formation were investigated. It was found that the ionic liquids shifted the hydrate equilibrium line to a lower temperature at a specific pressure, while simultaneously delaying gas hydrate formation.

An improved model for the phase equilibrium of methane hydrate inhibition in the presence of ionic liquids

“…The developed phase stability model is validated with experimental data on the phase stability conditions form methane hydrate in the presence of 21 ILs as reported in literatures [7,[11][12][13]15,16,21]. The ILs considered are from different ionic family such as, tetraalkylammonium, pyrrolidinium, imidazolium cationic family with various anion group such as halides (Cl, Br, I), sulphate (HSO 4 , ethylsulphate), tetrafluoroborate (BF 4 ) and dicyanamide (DCA).…”

“…(12) [35]. ln a w ð Þ ¼ Àv I mM w 1000 ' (12) where, M w is the molecular weight of water, ' is the osmotic coefficient, m is the molality and v I is the number of ions in IL formula. Osmotic coefficient obtained from Pitzer-Mayorga model is shown in Eqs.…”

“…Further, the developed liquid phase activity model is used to compute the fugacity of the liquid phase, and the fugacity of hydrate phase is computed from modified van der Waals and Platteuw model coupled with PR-EoS which is used for fugacity of hydrate former (gas phase) for the prediction of methane hydrate phase stability conditions in the presence of ILs. The model predictions are compared with experimental results on the phase stability of methane hydrate reported in open literatures for 21 ILs [7,[11][12][13]15,16,21]. The effect of 21 ILs with different concentration range from 5% to 20% (Table 1) are chosen from various ionic groups such as tetraalkylammonium, pyrrolidinium, imidazolium cationic family with various anion group such as halides (Cl, Br, I), sulphate (HSO 4 , ethylsulphate), tetrafluoroborate (BF 4 ) and dicyanamide (DCA), are considered from open literature for modeling the phase stability of methane hydrate inhibition.…”

“…Their study revealed that ILs must have strong electrolyte charges and capable of hydrogen bonding with the water molecule which causes the shift in H-L-V equilibrium conditions to a lower temperature at a given pressure and also slow down the hydrate nucleation growth rates. Kim et al [12] hypothesized the following criteria for better inhibition of methane hydrate in the presence of ILs: (i) IL is hydrophilic and (ii) cation is capable of creating intermolecular hydrogen bonding with water molecules. Based on this hypothesis, their studies on pyrrolidinium based ILs showed better thermodynamic inhibition effect on methane hydrate.…”

Synthesis and application of a novel combined kinetic hydrate inhibitor

“…Various kinds of KHIs have been developed, such as poly(vinylpyrrolidone) (PVP) [8,9] and polyvinylcaprolactan (PVCap) [10,11], which represent the inhibitors of low dosage, high efficiency and low cost. Moreover, antifreeze proteins [12,13] and ionic liquids [14][15][16] etc. as hydrate inhibitors provide a guideline for the development of new green KHIs recently.…”