Rapid Formation of Hydrogen-Enriched Hydrocarbon Gas Hydrates under Static Conditions

Abstract

This work introduces a "hydrate seed solution", a surfactant solution containing pre-constructed structure II (sII) hydrate crystals, for the rapid formation of hydrogen-enriched hydrocarbon mixed hydrates. We observed the instantaneous nucleation and fast growth of mixed gas hydrates for both CH 4 − H 2 and C 2 H 6 −H 2 mixtures with the cyclopentane (CP) hydrate seed. The CP hydrate seed, which is immiscible with water, dominantly induces the growth of CH 4 −H 2 and C 2 H 6 −H 2 mixed gas hydrates with thermodynamically favorable sI structure. However, the THF hydrate seed, which is miscible with water, induced the formation of seed-templated sII CH 4 −H 2 or C 2 H 6 − H 2 hydrate, and the overall reaction was much slower than the CP hydrate seed case. For the C 2 H 6 −H 2 gas mixture, C 2 H 6 molecules could not occupy the small cage of hydrates, but H 2 mainly occupied the small cage. The THF hydrate seed provided a higher storage ratio of H 2 than the CP hydrate seed because the seed-templated sII C 2 H 6 −H 2 gas hydrates have a larger number of small cages than does the structure I (sI) hydrate. As the CP hydrate seed concentration decreased from 2.78 to 0.278 mol %, the growth of the mixed gas hydrates was extremely accelerated, and the overall conversion was completed within 1 h. The growth kinetics of hydrogen-enriched hydrocarbon mixed hydrates in the non-stirred system was much faster than that in prior agitation-applied studies. These findings suggest a way forward to an enhanced formation of hydrogen−natural gas clathrates for sustainable energy gas storage.

A Rheological Study of Parameters That Influence the Formation of Cyclopentane Hydrates

“…It is also important to indicate that during the subzero temperature pretreatment stage, CP hydrate particles were formed and remained stable after the heating when the final temperature was achieved (until the temperature of 5 °C for our system, as noted in Figure ). Besides ice, these CP hydrate crystals likely facilitate the growth of CP hydrates, as it has been demonstrated in gas hydrate systems. , …”

“…Besides ice, these CP hydrate crystals likely facilitate the growth of CP hydrates, as it has been demonstrated in gas hydrate systems. 44,45 To evaluate the undesired presence of ice in the hydrate tests (step 7 of Figure 1), some experiments at the same conditions as those in Figure 2 were performed, as shown in Figure 3. First, an emulsion with CP was used without the subzero temperature pretreatment (STP).…”

Surface Science in the Research and Development of Hydrate-Based Sustainable Technologies

“…Methane-bearing natural hydrates in the seabed and permafrost sediments present a vast source of “frozen energy” that is much cleaner than conventional fossil fuels such as coal and crude oil. − These natural hydrates are seen as a source of cleaner energy for the future. Synthetic hydrates, on the other hand, enable the development of more sustainable production processes. − For example, hydrogen can be loaded into hydrate structures up to 4.3 wt %, offering a rare opportunity for a safe and efficient hydrogen storage technology. , Such a novel way of hydrogen storage is important for the development of hydrogen economy in which the storage of hydrogen is a standing challenge. − Likewise, the use of hydrates for capturing and storing carbon dioxide has been proven to be energy-efficient. − ,− Besides these usages, hydrates create notable challenges for sustainability. Vast volumes of natural hydrates on Earth pose a significant environmental hazard due to potential mass releases of methane as a potent greenhouse gas. , The formation of hydrates in oil and gas pipelines leads to flow blockages and severe impacts on drilling operations and the marine environment. − …”

Sulfonated Castor Oil as an Efficient Biosurfactant for Improving Methane Storage in Clathrate Hydrates

“…However, the slow kinetics of gas hydrate formation is one of the most serious obstacles to implementing this technology. − Therefore, the hydrate community has focused on using special additives, namely, gas hydrate promoters (GHPs), that can accelerate the hydrate formation. , GHPs are divided into thermodynamic and kinetic types . Thermodynamic GHPs such as tetrahydrofuran, tetra- n -alkyl ammonium halides, and cyclopentane alter the equilibrium conditions of gas hydrate formation toward higher temperatures and lower pressures. − This means that they provide milder conditions for the hydrate formation, but the gas capacity of the hydrate decreases . However, the rate of hydrate formation and the high degree of conversion of water to hydrate are critical technological parameters for hydrate-based technology .…”