Inhibition Effect of Synthesized Ionic Liquids on Hydrate Formation: A Kinetic and Thermodynamic Study

Abstract

In recent years, ionic liquids (ILs) are considered as potential thermodynamic and kinetic inhibitors of gas hydrate formation because of their unique molecular properties. In the present study, the effect of two ILs, namely, 1-methyl-3octylimidazolium tetrafluoroborate (C 8 mimBF 4 ) and 1-methyl-3-dodecylimidazolium tetrafluoroborate (C 12 mimBF 4 ), on the formation and dissociation of hydrates thermodynamically and kinetically has been investigated. The influence of C 8 mimBF 4 IL on induction time, hydrate formation rate, gas consumption, and water to hydrate and gas to hydrate conversion and enthalpy are investigated, and all the results are compared with a pure water system. The study reveals that the performance of IL solutions in hydrate inhibition is effective and has the ability to prevent the formation of hydrates both thermodynamically and kinetically. The results show that ILs significantly increase the induction time and the initial hydrate formation rate compared to the pure water system. The hydrate inhibition performance of ILs increases with increasing alkyl chain length, as the surface adsorption capacity on the hydrate crystal surface increases with enhanced alkyl chain length. The induction time of hydrate formation in the presence of 1 wt % of C8 and C12 ILs is 0.96 and 1.23 h, respectively. The investigated ILs with imidazolium-based cations have a higher impact on reducing the formation rate and rate constant in comparison with pure water.

Mechanical Characteristics of Underconsolidated Methane Hydrate-Bearing Clayed-Silty Sediments

“…From the experimental results, the φ of hydrate-bearing and hydrate-free sediments is 17.74°, cohesion c values are 1.01, 1.035, and 1.13 MPa for the hydrate-bearing sediments, and they are 0.945, 0.96, and 1 MPa for the hydrate-free sediments. By incorporating the relationship between the c, φ, and degree of consolidation to the Mohr−Coulomb failure criterion, the cohesion c connected to the degree of consolidation of underconsolidated MHBSs can be obtained for the hydratebearing (7)…”

“…Natural gas hydrates (cage compounds) are transparent or translucent solid compounds formed by hydrogen bonding of guest molecules such as methane gas or carbon dioxide with water. − In the natural environment, gas hydrate exists stably in the form of methane and water crystallization under low-temperature and high-pressure conditions, which is also widely distributed in offshore areas and permafrost zones. − Under the background of the exhaustion of traditional fossil resources and continuously increasing energy demand, − as a clean and efficient unconventional fossil energy with wide distribution and large reserves, natural gas hydrate can provide critical support for solving the energy shortage problem. , However, the geological characteristics of hydrate-bearing sediments are complex and the sedimentary environment is sensitive, , and the exploitation of hydrate is accompanied by the decomposition of hydrate. , The decomposition of hydrate will reduce the sediment strength, which will lead to landslide, deposition, and another marine geological disaster. − Therefore, the study of the mechanical characteristics of methane hydrate-bearing sediment (MHBS) under triaxial stress is of great importance to the safety and stability exploitation and commercialization of hydrate engineering …”