Facilitating clathrate hydrates with extremely rapid and high gas uptake for chemical-free carbon capture and methane storage

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Clathrate hydrates, ice-like crystalline compounds of hydrogen-bonded water, have a great potential for carbon capture and sequestration since they selectively capture CO 2 from mixtures and produce clean water as major byproducts. However, as the rate and amount of CO 2 gas uptake in hydrates are insufficient for practical uses, improving the hydrate formation kinetics with proper additives is necessary. Hydrophobic amino acids were proposed as environmentally friendly kinetic promoters, but their performances differ significantly in each reported paper since the kinetics of hydrate formation is greatly affected by the testing environment, including the reactor type and geometry, stirring condition, temperature, pressure, driving force, and amino acid concentration. Here, the effects of hydrophobic amino acids on accelerating CO 2 hydrate formation were systematically characterized under isochoric/isobaric and stirred/nonstirred conditions with different mixing rates. According to the results, weakly hydrophobic amino acids were more effective due to the increase in local CO 2 concentration and the clathrate-like structural ordering of water. While the formation of a CO 2 hydrate film at the gas−liquid interface often limits mass transfer, adding 1 wt % Ltryptophan led to a 126-fold increase in CO 2 uptake by facilitating interfacial diffusion. The maximum CO 2 uptake under nonstirred condition was 60 mmol CO 2 /mol H 2 O, and the optimal L-tryptophan concentration was derived as 0.1−1.0 wt %. The formation of porous CO 2 hydrates with hydrophobic amino acids under nonstirred condition was hypothesized: (1) porous hydrates form rapidly and (2) the liquid water gradually converts into hydrates. The environmental friendliness of amino acids and their property of not generating excessive foam would be highly preferred to utilize hydrates for carbon capture and sequestration.

Section: Results and Discussionmentioning

confidence: 99%

Section: Hydrate Formation In An Isochoric System Under Stirred Condi...mentioning

confidence: 99%

Promotion Effects of Hydrophobic Amino Acids on CO₂ Hydrate Formation Kinetics under Isochoric/Isobaric and Stirred/Nonstirred Conditions

Cho,

Kim,

2023

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“…4,5 The crystal structures of clathrate hydrates are mainly sI, sII, and sH, but other uncommon crystal structures like structures III−VII and T have also been reported to form for some guests under certain conditions. 1,6 Clathrate hydrate has potential applications in energy storage, 7,8 gas separation, 9,10 CO 2 capture and sequestration, 11,12 water desalination, 13,14 and others. On the other hand, in the oil and gas industry, the formation of natural gas hydrates could cause flow assurance problems in flow lines and destroy the structural integrity of the pipelines or surface facilities if it is not controlled properly.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Clathrate hydrate has potential applications in energy storage, , gas separation, , CO 2 capture and sequestration, , water desalination, , and others. On the other hand, in the oil and gas industry, the formation of natural gas hydrates could cause flow assurance problems in flow lines and destroy the structural integrity of the pipelines or surface facilities if it is not controlled properly .…”

Section: Introductionmentioning

confidence: 99%

Nucleation of CO₂ Hydrate in Quasi-Free Droplets of Dilute Electrolytes

Zhang,

Li,

Maeda

2024

Salts are known to be thermodynamic inhibitors of gas hydrates at high concentrations by lowering the activity of water and shifting the phase boundary of gas hydrates to lower temperatures and higher pressures. However, some salts have been reported to kinetically promote the formation of gas hydrates at low concentrations. Studies on kinetic promotions of clathrate hydrate formation in dilute salt solutions are rare, and the mechanisms are poorly understood. The impact of solid walls on heterogeneous nucleation of gas hydrates is complex and depends on the nature of the solid walls, and it is difficult to decouple the impact of solid walls from that of dilute electrolytes when they are present. In particular, a solid wall often becomes charged when in contact with an aqueous phase, and the binding of the counterions to the solid wall in an aqueous phase further complicates the investigations of heterogeneous nucleation of gas hydrates. Here, we investigated the nucleation rates of CO2 hydrate in quasi-free droplets of sodium chloride (NaCl) and potassium iodide (KI) at low concentrations (≤10 mM). The results showed that NaCl solution had no inhibition effect while KI solution had a weak promotion effect at low concentrations, and the nucleation rates were largely independent of the salt concentrations up to 10 mM. The impacts of dilute NaCl and KI solutions on the nucleation of CO2 hydrate in this study were broadly similar to the previous findings of the methane–propane mixed gas hydrates in Sowa et al.’s study.

“…Gas hydrates (GHs) or clathrates are nonstoichiometric ice-like solid compounds that were discovered in permafrost/marine sediments (as a source of energy) and in oil and gas pipelines (as flow assurance problems). , GHs are formed by water and gas molecules at specific pressure and temperature conditions wherein water molecules form hydrogen-bonded cages in which the gas molecule is encapsulated and stabilized by van der Waals interactions . GHs have received significant attention due to their potential industrial applications (e.g., CO 2 capture/gas separation, CO 2 sequestration, seawater desalination, and natural gas storage and transport) and problems in oil and gas pipelines. − …”

Section: Introductionmentioning

confidence: 99%

Investigating the Effect of Crown Ether on the Kinetics and Morphology of Natural Gas Hydrate Formation

Dubey,

Bhandari,

Gurjar

et al. 2023

In the field of gas hydrate research, additives have gained significant attention due to their exceptional promotional and inhibition effects in hydrate-based applications and flow assurance problems in the oil and gas industries, respectively. Therefore, in this work, we evaluate the performance of a new chemical (crown ether) for natural gas hydrate formation kinetics and morphology. A high-pressure stirred tank reactor with visual windows was employed to examine the performance of 18-crown-6ether (CE) for the formation kinetics of natural gas hydrate at high water-cut and high subcooling (∼21 K). Cyclopentane (1.5 mol % CP) was used as an additional hydrate former/oil phase. Experiments were conducted by using isothermal and cooling−heating methods of hydrate formation and dissociation. Various concentrations of CE, with a dosage ranging from 0.05 to 2.0 wt %, were assessed for hydrate formation kinetics, hydrate onset temperature, and morphological modifications. Cooling−heating experiments reveal that the hydrate onset temperature was significantly reduced in the presence of CE (60−70% reduction with respect to the baseline). Moreover, the hydrate formation kinetics/rate of hydrate growth was also reduced significantly in the presence of CE. Further, a unique behavior of CE was observed for the experiments performed in saline water (3.5 wt % NaCl in water). In saline water, hydrate formation kinetics was found to reduce in the presence of a low concentration of CE (0.05 wt %), while an enhanced growth rate was observed with a high concentration of CE (1.0 wt %). Our results may offer new insights into the usage of CE for various hydrate-based technologies as well as to manage hydrate formation in oil and gas pipelines.