Phase equilibria in ternary (carbon dioxide + tetrahydrofuran + water) system in hydrate-forming region: Effects of carbon dioxide concentration and the occurrence of pseudo-retrograde hydrate phenomenon

In the present work, the three- and four-phase hydrate equilibria of (carbon dioxide (CO₂) + tetrahydrofuran (THF) + water) system are measured by using Cailletet equipment in the temperature and pressure range of (272 to 292) K and (1.0 to 7.5) MPa, respectively, at different CO₂ concentration. Throughout the study, the concentration of THF is kept constant at 5 mol% in the aqueous solution. In addition, the fluid phase transitions of L_W–L_V–V → L_W–L_V (bubble point) and L_W–L_V–V → L_W–V (dew point) are determined when they are present in the ternary system. For comparison, the three-phase hydrate equilibria of binary (CO₂ + H₂O) are also measured. Experimental measurements show that the addition of THF as a hydrate promoter extends hydrate stability region by elevating the hydrate equilibrium temperature at a specified pressure. The three-phase equilibrium line H–L_W–V is found to be independent of the overall concentration of CO₂. Contradictory, at higher pressure, the phase equilibria of the systems are significantly influenced by the overall concentration of CO₂ in the systems. A liquid–liquid phase split is observed at overall concentration of CO₂ as low as 3 mol% at elevated pressure. The region is bounded by the bubble-points line (L_W–L_V–V → L_W–L_V), dew points line (L_W–L_V–V → L_W + V) and the four-phase equilibrium line (H + L_W + L_V + V). At higher overall concentration of CO₂ in the ternary system, experimental measurements show that pseudo-retrograde behaviour exists at pressure between (2.5 and 5) MPa at temperature of 290.8 K.     

Phase equilibria for H2 + CO2 + H2O system containing gas hydrates

Isothermal phase equilibrium (pressure–composition in the gas phase) for the ternary system of H₂ + CO₂ + H₂O has been investigated in the presence of gas hydrate phase. Three-phase equilibrium pressure increases with the H₂ composition of gas phase. The Raman spectra suggest that H₂ is not enclathrated in the hydrate-cages and behaves only like the diluent gas toward the formation of CO₂ hydrate. This fact is also supported by the thermodynamic analysis using Soave–Redlich–Kwong equation of state.     

Hydrate phase equilibrium for the (hydrogen + tert-butylamine + water) system

The three-phase equilibrium conditions of ternary (hydrogen + tert-butylamine + water) system were first measured under high-pressure in a “full view” sapphire cell. The tert-butylamine–hydrogen binary hydrate phase transition points were obtained through determining the points of intersection of three phases (H–L_w–V) to two phases (L_w–V) experimentally. Measurements were made using an isochoric method. Firstly, (tetrahydrofuran + hydrogen) binary hydrate phase equilibrium data were determined with this method and compared with the corresponding experimental data reported in the literatures and the acceptable agreements demonstrated the reliability of the experimental method used in this work. The experimental investigation on (tert-butylamine + hydrogen) binary hydrate phase equilibrium was then carried out within the temperature range of (268.4 to 274.7) K and in the pressure range of (9.54 to 29.95) MPa at (0.0556, 0.0886, 0.0975, and 0.13) mole fraction of tert-butylamine. The three-phase equilibrium curve (H + L_w + V) was found to be dependent on the concentration of tert-butylamine solution. Dissociation experimental results showed that tert-butylamine as a hydrate former shifted hydrate stability region to lower pressure and higher temperature.     

Hydrate phase equilibrium in the system of (carbon dioxide + 2,2-dimethylbutane + water) at temperatures below freezing point of water

The four-phase equilibrium conditions of (vapor + liquid + hydrate + ice) were measured in the system of (CO₂ + 2,2-dimethylbutane + water). The measurements were performed within the temperature range (254.2 to 270.2) K and pressure range (0.490 to 0.847) MPa using an isochoric method. Phase equilibrium conditions of hydrate formed in this study were measured to be at higher temperatures and lower pressures than those of structure I CO₂ simple hydrate. The largest difference in the equilibrium pressures of structure I CO₂ hydrate and the hydrate formed in the present study was 0.057 MPa at T = 258.3 K. On the basis of the four-phase equilibrium data obtained, the quintuple point for the (ice + structure I hydrate + structure H hydrate + liquid + vapor) was also determined to be T = 266.4 K and 0.864 MPa. The results indicate that structure H hydrate formed with CO₂ and 2,2-dimethylbutane is stable exclusively at the temperatures below the quintuple temperature.     

The P, V, T,x properties of binary aqueous chloride solutions up to T = 573 K and 100 MPa

A highly accurate P, V, T,x model is developed for aqueous chloride solutions of the binary systems, viz. (LiCl + H₂O), (NaCl + H₂O), (KCl + H₂O), (MgCl₂ + H₂O), (CaCl₂ + H₂O), (SrCl₂ + H₂O), and (BaCl₂ + H₂O). The applied ranges of temperature, pressure, and concentrations for the systems (LiCl + H₂O), (NaCl + H₂O), (KCl + H₂O), (MgCl₂ + H₂O), (CaCl₂ + H₂O), (SrCl₂ + H₂O), and (BaCl₂ + H₂O) are (273 K to 564 K, 0.1 MPa to 40 MPa, and 0 to 10 molal), (273 K to 573 K, 0.1 MPa to 100 MPa, and 0 to 6.0 molal), (273 K to 543 K, 0.1 MPa to 50 MPa, and 0 to 4.5 molal), (273 K to 543 K, 0.1 MPa to 40 MPa, and 0 to 3.0 molal), (273 K to 523 K, 0.1 MPa to 60 MPa, and 0 to 6.0 molal), (298 K to 473 K, 0.1 MPa to 2 MPa, and 0 to 2.0 molal) and (273 K to 473 K, 0.1 MPa to 20 MPa, and 0 to 1.6 molal), respectively. Comparison of the model with thousands of experimental data points concludes that the average deviation over the above T, P, m range is 0.020% to 0.066% in density (or volume) for these systems, which indicates high accuracy. From this model, various volumetric properties, such as the apparent molar volume at infinite dilution and isochores of fluid inclusions, can be calculated, thus having a wide range of geological applications, such as reservoir fluid flow simulation and fluid-inclusion study. A computer code is developed for this model and can be downloaded from the website: www.geochem-model.org/programs.htm and online calculations is made available on: www.geochem-model.org/models.htm     

Isothermal phase equilibria for the (xenon + cyclopropane) mixed-gas hydrate system

Isothermal three-phase equilibria of gas, aqueous, and hydrate phases for the {xenon (Xe) + cyclopropane (c-C₃H₆)} mixed-gas hydrate system were measured at two different temperatures (279.15 and 289.15) K. The structural phase transitions from structure-I to structure-II and back to structure-I, depending on the mole fraction of guest mixtures, occur in the (Xe + c-C₃H₆) mixed-gas hydrate system. The isothermal pressure–composition relations have two local pressure minima. The most important characteristic in the (Xe + c-C₃H₆) mixed-gas hydrate system is that the equilibrium pressure–composition relations exhibit the complex phase behavior involving two structural phase transitions and two homogeneous negative azeotropes. One of two structural phase transitions exhibits the heterogeneous azeotropic-like behavior.     

The partition coefficients of ethylene between vapor and hydrate phase for methane + ethylene + THF + water systems

The vapor-hydrate equilibria were studied experimentally in detail for CH₄ + C₂H₄ + tetrahydrofuran (THF) + water systems in the temperature range of 273.15–282.15 K, pressure range of 2.0–4.5 MPa, the initial gas–liquid volume ratio range of 45–170 standard volumes of gas per volume of liquid and THF concentration range of 4–12 mol%. The results demonstrated that, because of the presence of THF, ethylene was remarkably enriched in vapor phase instead of being enriched in hydrate phase for CH₄ + C₂H₄ + water system. This conclusion is of industrial significance; it implies that it is feasible to enrich ethylene from gas mixture, e.g., various kinds of refinery gases or cracking gases in ethylene plant, by forming hydrate.     

Phase equilibrium for ozone-containing hydrates formed from an (ozone + oxygen) gas mixture coexisting with gaseous carbon dioxide and liquid water

The paper reports the three-phase (gas + aqueous liquid + hydrate) equilibrium pressure (p) versus temperature (T) data for a (O₃ + O₂ + CO₂ + H₂O) system and, for comparison, corresponding data for a (O₂ + CO₂ + H₂O) system for the first time. These data cover the temperature range from (272 to 279) K, corresponding to pressures up to 4 MPa, for each of the three different (O₃ + O₂)-to-CO₂ or O₂-to-CO₂ mole ratios in the gas phase, which are approximately 1:9, 2:8, and 3:7, respectively. The mole fraction of ozone in the gas phase of the (O₃ + O₂ + CO₂ + H₂O) system was from ∼0.004 to ∼0.02. The modified pressure-search method, developed in our previous study [S. Muromachi, T. Nakajima, R. Ohmura, Y.H. Mori, Fluid Phase Equilib. 305 (2011) 145–151] for p–T measurements in the presence of chemically unstable ozone, was applied, having been further modified for dealing with highly water-soluble CO₂, for the (O₃ + O₂ + CO₂ + H₂O) system, while the conventional temperature-search method was used for the (O₂ + CO₂ + H₂O) system. The measurement uncertainties (with 95% coverage) were ±0.11 K for T, ±6.0 kPa for p, and ±0.0015 for the mole fraction of each species in the gas phase. It was confirmed that, at a given CO₂ fraction in the gas phase, p for the (O₃ + O₂ + CO₂ + H₂O) system was consistently lower than that for the (O₂ + CO₂ + H₂O) system over the entire T range of the present measurements, indicating a preference of O₃ to O₂ in the uptake of guest-gas molecules into the cages of a structure I hydrate.     

A thermodynamic model for calculating nitrogen solubility,gas phase composition and density of the N2–H2O–NaCl system

A thermodynamic model is presented to calculate N₂ solubility in pure water (273–590 K and 1–600 bar) and aqueous NaCl solutions (273–400 K, 1–600 bar and 0–6 mol kg⁻¹) with or close to experimental accuracy. This model is based on a semi-empirical equation used to calculate gas phase composition of the H₂O–N₂ system and a specific particle interaction theory for liquid phase. With the parameters evaluated from N₂–H₂O–NaCl system and using a simple approach, the model is extended to predict the N₂ solubility in seawater accurately. Liquid phase density of N₂–H₂O–NaCl system at phase equilibrium and the homogenization pressure of fluid inclusions containing N₂–H₂O–NaCl can be calculated from this model. A computer code is developed for this model and can be downloaded from the website: www.geochem-model.org/programs.htm.     

Inhibition effect of 1-ethyl-3-methylimidazolium chloride on methane hydrate equilibrium

The dissociation conditions of methane hydrate in the presence of 0.1, 0.2, 0.3 and 0.4 mass fraction of 1-ethyl-3-methylimidazolium chloride (abbreviated by EMIM-Cl hereafter) were experimentally determined. A high pressure micro-differential scanning calorimeter equipped with a motorized pump was applied to measure the dissociation temperature of the (hydrate + liquid water + vapor) three-phase equilibrium under a constant pressure process with a pressure ranging from (5.0 to 35.0) MPa. The addition of EMIM-Cl would inhibit the methane hydrate formation. The most significant inhibition effect was observed at 0.4 mass fraction of EMIM-Cl in aqueous solution to lower the dissociation temperature by 12.82 K at 20.00 MPa in comparison to that of the (methane + water) system. The Peng–Robinson–Stryjek–Vera equation of state incorporated with COSMO-SAC activity coefficient model and the first order modified Huron–Vidal mixing rule were applied to evaluate the fugacity of vapor and liquid phase. A modified van der Waals and Platteeuw model with an explicit pressure dependence of the Langmuir adsorption constant was applied to determine the fugacity of hydrate phase. The predictive thermodynamic model successfully describes the tendency of phase behavior of methane hydrate in the presence of EMIM-Cl in the range from 0.1 to 0.4 mass fraction with absolute average relative deviation in predicted temperature of 0.70%.     

Modelling of the phase behaviour for the direct synthesis of dimethyl carbonate from CO2 and methanol at supercritical or near critical conditions

This study is focused on modelling the phase equilibrium behaviour of the reaction mixture (CO₂ + methanol + DMC + H₂O) at high pressure–temperature conditions using the Patel–Teja (PT) and Peng–Robinson–Stryjek–Vera (PRSV) equations of state along with the van der Waals One-Fluid (1PVDW) mixing rule. The optimum values of the binary interaction parameters (k_ij) were calculated from VLE data found in the literature, and then adjusted to a lineal temperature equation. As a result, the temperature-dependent model was applied to predict the fluid phase equilibria of the corresponding binary a ternary sub-systems and, later, successfully contrasted with experimental data. In addition, phase equilibrium data were experimentally measured at high pressure (8 MPa to 15 MPa) for the ternary system (CO₂ + methanol + DMC), in order to confirm the ability of the model to predict the phase behaviour of the ternary system at high pressure–temperature. The agreement between the experimental data and the proposed model enables to predict the phase equilibrium behaviour of the mixture (CO₂ + methanol + DMC + H₂O), and thus, optimise the operation conditions in several reaction and separation processes.     

Experimental observations on the competing effect of tetrahydrofuran and an electrolyte and the strength of hydrate inhibition among metal halides in mixed CO2 hydrate equilibria

In the present work, experimental data on the equilibrium conditions of mixed CO₂ and THF hydrates in aqueous electrolyte solutions are reported. Seven different electrolytes (metal halides) were used in this work namely sodium chloride (NaCl), calcium chloride (CaCl₂), magnesium chloride (MgCl₂), potassium bromide (KBr), sodium fluoride (NaF), potassium chloride (KCl), and sodium bromide (NaBr). All equilibrium data were measured by using Cailletet apparatus. Throughout this work, the overall concentration of CO₂ and THF were kept constant at (0.04 and 0.05) mol fraction, respectively, while the concentration of electrolytes were varied. The experimental temperature ranged from (275 to 305) K and pressure up 7.10 MPa had been applied. From the experimental results, it is concluded that THF, which is soluble in water is able to suppress the salt inhibiting effect in the range studied. In all quaternary systems studied, a four-phase hydrate equilibrium line was observed where hydrate (H), liquid water (L_W), liquid organic (L_V), and vapour (V) exist simultaneously at specific pressure and temperature. The formation of this four-phase equilibrium line is mainly due to a liquid–liquid phase split of (water + THF) mixture when pressurized with CO₂ and the split is enhanced by the salting-out effect of the electrolytes in the quaternary system. The strength of hydrate inhibition effect among the electrolytes was compared. The results shows the hydrate inhibiting effect of the metal halides is increasing in the order NaF < KBr < NaCl < NaBr < CaCl₂ < MgCl₂. Among the cations studied, the strength of hydrate inhibition increases in the following order: K⁺ < Na⁺ < Ca²⁺ < Mg²⁺. Meanwhile, the strength of hydrate inhibition among the halogen anion studied decreases in the following order: Br^? > Cl^? > F^?. Based on the results, it is suggested that the probability of formation and the strength of ionic–hydrogen bond between an ion and water molecule and the effects of this bond on the ambient water network are the major factors that contribute to hydrate inhibition by electrolytes.     

Thermodynamic study of the system (LiCl + LiNO3 + H2O)

The solubility of the binary system (LiNO₃ + H₂O) from T = 273.15 K to T = 333.15 K and solubility isotherms of the ternary system (LiCl + LiNO₃ + H₂O) were elaborately measured at T = 273.15 K and T = 323.15 K. These solubility data, as well as water activities in the binary systems from the literature, were treated by an empirically modified BET model. The isotherms of the ternary system (LiCl + LiNO₃ + H₂O) were reproduced and a complete phase diagram of the ternary system in the temperature range from 273.15 K to 323.15 K predicted. It is shown that the solubility data for the binary system (LiNO₃ + H₂O) measured in this work are slightly different from the literature data. Simulated results showed that the saturated salt solution of (2.8LiCl + LiNO₃) is in equilibrium with the stable solid phase LiNO₃(s) over the temperature range from 283.15 K to 323.15 K, other than the solid phases LiNO₃ · 3H₂O(s) and LiClH₂O(s) as reported by Iyoki et al. [S. Iwasaki, Y. Kuriyama. T. Uemura, J. Chem. Eng. Data 38 (1993) 396–398].     

Phase equilibrium measurements for semi-clathrate hydrates of the (CO2 + N2 + tetra-n-butylammonium bromide) aqueous solution system

The application of semi-clathrate hydrate formation technology for gas separation purposes has gained much attention in recent years. Consequently, there is a demand for experimental data for relevant semi-clathrate hydrate phase equilibria. In this work, semi-clathrate hydrate dissociation conditions for the system comprising mixtures of {CO₂ (0.151/0.399 mole fraction) + N₂ (0.849/0.601 mole fraction) + 0.05, 0.15, and 0.30 mass fraction tetra-n-butylammonium bromide (TBAB)} aqueous solutions have been measured and are reported. An experimental apparatus which was designed and built in-house was used for the measurements using the isochoric pressure-search method. The range of conditions for the measurements was from 277.1 K to 293.2 K for temperature and pressures up to 16.21 MPa. The phase equilibrium data measured demonstrate the high hydrate promotion effects of TBAB aqueous solutions.     

Study of bromide salts solubility in the (m1NaBr + m2MgBr2)(aq) system at T = 323.15 K. Thermodynamic model of solution behavior and (solid + liquid) equilibria in the (Na + K + Mg + Br + H2O) system to high concentration and temperature

The bromide minerals solubility in the mixed system (m₁NaBr + m₂MgBr₂)(aq) have been investigated at T = 323.15 K by the physico-chemical analysis method. The equilibrium crystallization of NaBr·2H₂O(cr), NaBr(cr), and MgBr₂·6H₂O(cr) has been established. The solubility-measurements results obtained have been combined with all other experimental equilibrium solubility data available in literature at T = (273.15 and 298.15) K to construct a chemical model that calculates (solid + liquid) equilibria in the mixed system (m₁NaBr + m₂MgBr₂)(aq). The solubility modeling approach based on fundamental Pitzer specific interaction equations is employed. The model gives a very good agreement with bromide salts equilibrium solubility data. Temperature extrapolation of the mixed system model provides reasonable mineral solubility at high temperature (up to 100 °C). This model expands the previously published temperature variable sodium–potassium–bromide and potassium–magnesium–bromide models by evaluating sodium–magnesium mixing parameters. The resulting model for quaternary system (Na + K + Mg + Br + H₂O) is validated by comparing solubility predictions with those given in literature, and not used in the parameterization process. Limitations of the mixed solution models due to data insufficiencies at high temperature are discussed.     

Phase behaviour of mixed-gas hydrate systems containing carbon dioxide

We describe a new apparatus suitable for measurements of the phase behaviour and phase properties of fluid mixtures under conditions of high-pressure. We propose a synthetic method for the determination of gas solubility, and present results for the system (CO₂ + H₂O). In addition, we report new measurements of the hydrate equilibrium curves in aqueous systems containing either pure carbon dioxide or mixed gases including CO₂. For hydrates formed in the (CO₂ + H₂O) system, we find an enthalpy of dissociation of 77 kJ · mol^?1. This value was unchanged by the addition of mass fraction 0.043 of NaCl to the water. Compared with pure CO₂, mixtures of CO₂ with air exhibited markedly different dissociation pressures at given temperature, but were characterised by the same enthalpy of dissociation. However, two mixtures containing either nitrogen or methane and hydrogen both exhibited a higher enthalpy of dissociation, 106 kJ · mol^?1, consistent with these systems forming structure II hydrates.     

Dissociation behaviour of (tetra-n-butylammonium bromide + tetra-n-butylammonium chloride) mixed semiclathrate hydrate systems

The thermal properties of {tetra-n-butylammonium bromide + tetra-n-butylammonium chloride (TBAB + TBAC)} mixed semiclathrate hydrates prepared from aqueous solutions were investigated by dissociation temperature measurements and differential scanning calorimetry (DSC). The maximum dissociation temperature of the mixed hydrate crystals at 0.1 MPa is 288.5 K for x_TBAB = 0.2 {mole fraction of TBAB to (TBAB + TBAC)}, which is higher than that of the pure hydrates {T = (285.5 and 288.2) K for TBAB and TBAC hydrates, respectively}. In addition, the dissociation enthalpies of the mixed hydrates are higher than those of the pure hydrates {(5.55 ± 0.06) kJ ⋅ mol⁻¹ H₂O for pure TBAB hydrate and (5.30 ± 0.05) kJ ⋅ mol⁻¹ H₂O for pure TBAC hydrate}, with a maximum of (5.95 ± 0.12) kJ ⋅ mol⁻¹ H₂O recorded at approximately x_TBAB = 0.4. It was therefore suggested that the crystal distortion in (TBAB + TBAC) mixed hydrates, caused by replacing water molecules by both bromide and chloride anions, was smaller than that observed for each pure hydrate. Consequently, the hydration numbers in the mixed hydrates were hypothesized to be slightly higher than those of the pure hydrates.     

Isopiestic measurement and solubility evaluation of the ternary system (CaCl2 + SrCl2 + H2O) at T = 298.15 K

Water activities in the ternary system (CaCl₂ + SrCl₂ + H₂O) and its sub-binary system (CaCl₂ + H₂O) at T = 298.15 K have been elaborately measured by an isopiestic method. The data of the measured water activity were used to justify the reliability of solubility isotherms reported in the literature by correlating them with a thermodynamic Pitzer–Simonson–Clegg (PSC) model. The model parameters for representing the thermodynamic properties of the (CaCl₂ + H₂O) system from (0 to 11) mol ⋅ kg⁻¹ at T = 298.15 K were determined, and the experimental water activity data in the ternary system were compared with those predicted by the parameters determined in the binary systems. Their agreement indicates that the PSC model parameters can reliably represent the properties of the ternary system. Under the assumption that the equilibrium solid phases are the pure solid phases (SrCl₂ ⋅ 6H₂O and CaCl₂ ⋅ 6H₂O)_(s) or the ideal solid solution consisting of CaCl₂ ⋅ 6H₂O_(s) and SrCl₂ ⋅ 6H₂O_(s), the solubility isotherms were predicted and compared with experimental data from the literature. It was found that the predicted solubility isotherm agrees with experimental data over the entire concentration range at T = 298.15 K under the second assumption described above; however, it does not under the first assumption. The modeling results reveal that the solid phase in equilibrium with the aqueous solution in the ternary system is an ideal solid solution consisting of SrCl₂ ⋅ 6H₂O_(s) and CaCl₂ ⋅ 6H₂O_(s). Based on the theoretical calculation, the possibility of the co-saturated points between SrCl₂ ⋅ 6H₂O_(s) and the solid solution (CaCl₂ ⋅ 6H₂O + SrCl₂ ⋅ 6H₂O)_(s) and between CaCl₂ ⋅ 6H₂O_(s) and the solid solution (CaCl₂ ⋅ 6H₂O + SrCl₂ ⋅ 6H₂O)_(s), which were reported by experimental researchers, has been discussed, and the Lippann diagram of this system has been presented.     

Nanospace geometry-sensitive molecular assembly

Interaction of a molecule with micropore walls strongly depends on the micropore width. Molecules confined in the micropore tend to form an intermolecular structure inherent to each molecule/pore system in order to lower the whole molecular energy. Supercritical NO is adsorbed in micropores of zolite or activated carbon fiber in the form of a dimer at 303 K. The NO dimerization varies with the micropore width. CCl₄ molecules only in pore of pore width =1.0 nm at 303 K form a plastic crystalline structure which is observed at 246–250 K in the bulk phase. H₂O molecules are associated with each other to form an ordered assembly in carbon micropores at 303 K; the smaller the pore width, the more ordered the assembly structure. The presence of preadsorbed H₂O noticeably enhances adsorption of supercritical CH₄ in carbon micropores at 303 K due to methane nanohydrate formation, which has an optimum pore width of 1 nm.     

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 ⋅ mol⁻¹. There is no significant difference between the dissociation enthalpy of methane hydrate either in the presence or in absence of ILs.