The performance of ionic liquids and their mixtures in inhibiting methane hydrate formation

The performance of 1-ethyl-3-methylimidazolium chloride (EMIM-Cl), one of novel ionic liquid inhibitors for gas hydrate, in inhibiting methane hydrate at low and high ionic liquid concentrations is investigated in a pressure range of 10–20 MPa. Experiments on methane hydrate dissociation conditions in the presence of mixed ionic liquid and conventional inhibitors, such as sodium chloride (NaCl) and monoethylene glycol (MEG), as well as a mixture containing two ionic liquids, EMIM-Cl and 1-ethyl-3-methylimidazolium bromide (EMIM-Br), are also performed to investigate any possible synergistic effects. It is observed that single component solutions of EMIM-Cl demonstrate a progressive increase in inhibition effect with increasing concentration, which may surpass the effectiveness of MEG at high concentrations. Although the thermodynamic inhibition performance of the mixtures of EMIM-Cl and MEG does not show any synergistic effects at low pressures, it does at higher pressures. The mixture of EMIM-Cl and EMIM-Br also shows a synergistic effect at higher pressures. Unlike MEG or NaCl, inhibitors containing EMIM-Cl or EMIM-Br demonstrate an increase in inhibition effectiveness as pressure increases.

► EMIM-Cl could be more effective than MEG at high concentrations.
► The effectiveness of inhibitors containing EMIM-Cl increases with pressure.
► Synergistic effects are observed for EMIM-Cl and MEG at high pressures.
► Synergistic effects are observed for EMIM-Cl and EMIM-Br at high pressures.
► No synergistic effects are observed for EMIM-Cl and NaCl.