Experimental investigation on the dissociation conditions of methane hydrate in the presence of imidazolium-based ionic liquids

In this work, the performance of nine ionic liquids (ILs) as thermodynamic hydrate inhibitors is investigated.
The dissociation temperature is determined for methane gas hydrates using a high pressure micro
deferential scanning calorimeter between (3.6 and 11.2) MPa. All the aqueous IL solutions are studied at a
mass fraction of 0.10. The performance of the two best ILs is further investigated at various concentrations.
Electrical conductivity and pH of these aqueous IL solutions (0.10 mass fraction) are also measured.
The enthalpy of gas hydrate dissociation is calculated by the Clausius–Clapeyron equation. It is found that
the ILs shift the methane hydrate (liquid + vapour) equilibrium curve (HLVE) to lower temperature and
higher pressure. Our results indicate 1-(2-hydroxyethyl) 3-methylimidazolium chloride is the best
among the ILs studied as a thermodynamic hydrate inhibitor. A statistical analysis reveals there is a moderate
correlation between electrical conductivity and the efficiency of the IL as a gas hydrate inhibitor.
The average enthalpies of methane hydrate dissociation in the presence of these ILs are found to be in
the range of (57.0 to 59.1) kJ mol1. There is no significant difference between the dissociation enthalpy
of methane hydrate either in the presence or in absence of ILs.