Ionic liquids for the inhibition of gas hydrates. A review

The formation of hydrates in oil and gas transmission pipelines can cause blockage inside them and disrupt the normal flow. It may cause safety problems along with economic loss. To avoid these problems, it is necessary to have knowledge about gas hydrate formation. In this regard, hydrate liquid vapor equilibrium (HLVE) modeling can prove to be of significance as it predicts the phenomenon accurately. Dickens and Quinby-Hunt model is used to predict HLVE points. The experimental data has been obtained from open literature concerning inhibition of gas hydrates. The electrolytic binary solution mixtures of ionic liquids and quaternary ammonium salts (QAS) with commercial hydrate inhibitors have been taken into consideration. Methanol and mono ethylene glycol (MEG) are commercially used inhibitors. The gases forming hydrates include CO2, CH4 and mixed gas (CO2/CH4/N2). The experimental results are compared with the results obtained through modeling. The results show the applicability of the model as in case of QAS+MEG solution mixture hydrates with CO2, it shows a good fit. The HLVE findings by model for CH4 hydrates with EMIM-Cl+MEG solution mixture showed an average absolute error of less than 1% which is acceptable. The binary solution mixtures of NaCl+MEG, NaCl+MeOH and CaCl2+MeOH with tertiary gas mixture rich in CO2 were also modeled to find and compare the HLVE points from literature. It is found that the selected model is more suitable to be used in low pressure conditions and at high pressure, average absolute error (AAE) between experimental and modeling values is also high. It shows the suitability of the model and it can be further used in case of ionic compounds to predict hydrate inhibition behavior.

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Experimentally measured methane hydrate phase equilibria and ionic liquids inhibition performance in Qatar’s seawater

Scientific Reports ◽

10.1038/s41598-020-76443-1 ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

M. F. Qureshi ◽

M. Khraisheh ◽

F. AlMomani

Keyword(s):

Ionic Liquids ◽

Natural Gas ◽

Gas Hydrates ◽

Inductively Coupled Plasma ◽

Pure Water ◽

Artificial Seawater ◽

Inhibition Mechanism ◽

Inhibition Effect ◽

Ultra Pure Water ◽

The World

Abstract Qatar has the third-largest natural gas reserves in the world and is the second largest Liquefied natural gas (LNG) exporter in the world. These reserves are mainly located in its offshore North Field where the gas is extracted, transported to the onshore units, and is converted to LNG for international export. The formation of natural gas hydrates in the offshore subsea lines can cause unwanted blockages and hinder the smooth supply of gas supply from offshore to onshore units. In the present work, the formation and dissociation of methane gas hydrates have been studied in the ultra pure water system (UPW), artificial seawater (ASW), and Qatar seawater (QSW) at different conditions (4–10 MPa) using standard rocking cell rig. The naturally occurring seawater was collected from Ras Laffan seacoast located in Doha, Qatar. The seawater sample was examined for elemental analysis (SO4, Cl, Na, Ca, Mg, K, and Fe) using inductively coupled plasma atomic emission spectroscopy (ICP-AES) technique and its other properties like density, electrical conductivity, and pH were also measured. The experimental results show that the CH4 pure water HLVE curve is suppressed by about 3 K in Qatar seawater and 2 K in artificial seawater. The hydrate inhibition strength of the Ionic liquids (ILs) salts 3-Ethyl-1-methyl-1H-imidazol-3-ium methane-sulfonate [C7H14N2O3S] and 3-Ethyl-1-methyl-1H-imidazol-3-ium dicyanoazanide [C8H11N5] was evaluated in both the ultra pure water and Qatar seawater systems. Their performance was compared with methanol and other ILs salts reported in the literature. The selected ILs exhibited poor hydrate inhibition effect in the ultra pure water systems, but they show a noticeable thermodynamic and kinetic hydrate inhibition effect in the Qatar seawater system. The computational 3D molecular models of ILs and methanol were generated to cognize the plausible hydrate inhibition mechanism in the presence of these inhibitors.

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Study of 1-(2-Hydroxyethyle) 3-methylimidazolium Halide as Thermodynamic Inhibitors

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.625.337 ◽

2014 ◽

Vol 625 ◽

pp. 337-340 ◽

Cited By ~ 14

Author(s):

Omar Nashed ◽

Khalik Mohamad Sabil ◽

Bhajan Lal ◽

Lukman Ismail ◽

Azuraien Japper Jaafar

Keyword(s):

High Pressure ◽

Ionic Liquids ◽

Gas Hydrates ◽

Methane Hydrate ◽

Pressure Range ◽

Equilibrium Curve ◽

Dissociation Temperature ◽

Methane Gas Hydrates ◽

Lower Temperature ◽

Better Than

In this study, the performance of 1-(2-Hydroxyethyle) 3-methylimidazolium chloride [OH-EMIM][Cl] and 1-(2-Hydroxyethyle) 3-methylimidazolium bromide [OH-EMIM][Br] was investigated as thermodynamic gas hydrate inhibitors. The dissociation temperature was determined for methane gas hydrates using a high pressure micro deferential scanning calorimeter at a pressure range of 36-97 bar. Both ionic liquids (ILs) were studied at concentrations of 5, 10, 15, 20 and 25 wt% then their performance was compared with commercially available inhibitors. It was observed that both ILs shift the methane hydrate equilibrium curve to lower temperature and higher pressure; and the performance of [OH-EMIM][Cl] is better than [OH-EMIM][Br]. Nevertheless both of them were found to be less effective compared to methanol and mono ethylene glycol.

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