Facile and sustainable methane storage via clathrate hydrate formation with low dosage promoters in a sponge matrix

Natural gas (NG) is an effective and eco-friendly fossil fuel with regard to reducing CO2 emission. In this manner, many technologies have been developed to store the NG efficiently, like LNG and CNG. Among them, natural gas hydrates (NGH) emerge as a promising option to replace LNG and CNG, due to their high energy density and mild storage conditions. Nevertheless, vigorous mechanical stirring, which is typically adopted to produce the NGH, requires high energy inputs and short periodic managements from elevated viscosity of the fluids during the production process. In this work, the effective method for synthesizing methane hydrates under a non-stirred system was proposed and evaluated. A commercial melamine sponge, which is cheap, lightweight, and easily accessible, was utilized as a supporting matrix. Additionally, various types of thermodynamic (e.g., CP (immiscible) and THF (miscible) and kinetic promoters (e.g., sodium dodecyl sulfate (SDS, surfactant) and l-methionine (L-met, amino acid)) were introduced and assessed in terms of methane storage capacity and kinetic parameters during the long-term 20 cycles of formation-dissociation. These combinations from low dosage of thermodynamic and kinetic promoters (e.g., CP + SDS, and DIOX + L-met) facilitated immediate nucleation, and high methane uptake was obtained by inducing sequential growth of methane hydrates. Finally, comparing with the CNG technology, it was shown that the mixed hydrates formed with the low-dosage of promoters were profitable in terms of formation and storage conditions.