Enhanced methane storage in clathrate hydrates induced by antifreezes

Methane storage in clathrate hydrates containing water‐miscible oxirane promoters

“…The results (measured five times) are shown in Figure 10A and 14 As they demonstrated, the CH 4 uptake of the THF hydrates measured in this study also showed no particular tendency depending on the formation pressures. Considering that the CH 4 capacities of the THF + CH 4 hydrate measured by other researchers, 13,15,16,36,38 range from 42 to 80 mmol CH 4 /mol H 2 O, the values reported by Inkong et al 14 and this study appear to be the maximum practical storage level achievable with or without agitation. Here, it should be noted that (a) the CH 4 capacity of the EIB + CH 4 hydrate system increases as the external CH 4 pressure increases, and (b) it reaches its theoretical maximum value at a moderately high pressure of 80 bar, representing an approximately 20% higher capacity than the THF + CH 4 hydrate.…”

“…Many researchers have clearly demonstrated that the guest occupancy rates of a MH can be determined by integrating the areas of the 13 C NMR peaks from individual guests. 6,12,16,17,27,34,[36][37][38] Assuming that the overall occupancy rate of the sII-L cage should be approximately unity (Equation [1]), the occupancy rates of the LGM and CH 4 molecules in the sII-L cages (θ L,LGM and θ L,CH 4 , respectively) can be calculated from the ratio of the 13 C peak areas (Equation [2]). The occupancy rate of CH 4 in the sII-S cages (θ s,CH 4 ) can also be calculated using (Equation [3]).…”

“…As a part of this effort, Veluswamy et al 15 demonstrated that a slight addition of sodium dodecyl sulfate to the THF aqueous solution drastically increases the CH 4 uptake rate. Lee et al 16 recently demonstrated that the methane storage content in a THF hydrate system can be enhanced by adding a small amount of methanol or ammonia. Meanwhile, Seol et al 17,18 discovered several novel promoters containing an oxirane group (also commonly referred to as an epoxy group) in their molecular structures.…”

Zeolitic ice: A route toward net zero emissions

“…Although usually formed under high pressure, a combination of both experimental work and theoretical calculations in recent decades has enabled us to precisely determine the structure of those materials. Experimental techniques such as in situ NMR [52,53], X-ray diffraction [54,55] and Raman Spectroscopy [56,57] provided us with important information such as the nature of host structure, cage occupancy, and guest molecules motion in the cages . For example, Okuchi et al used in situ NMR single-crystal XRD (SXRD) was used to get the atomic coordinates and geometries that are not provided by the conventional spectroscopic techniques [58,59].…”

Effect of Methanol Guests on Thermal Properties of NH4F-Doped THF Clathrate Hydrate

“…For a long time, the hydrate community only focused on the inhibiting function of this additive and assumed that methanol just acts as an antifreeze similarly to its behavior in aqueous solutions. However, it was recently revealed that some antifreezes such as methanol and ammonia can be incorporated in the clathrate hydrates in the presence of other guest molecule such as tetrahydrofuran (THF) or propane that are able to form stable clathrate hydrates by themselves. , It was also revealed that those antifreeze molecules can actually enhance methane storing ability in some clathrate hydrates . These studies suggested that we should focus on the hydrate promotive effects of antifreezes on the hydrate applications as well as their inhibition functions.…”