Renewable biosurfactants for energy-efficient storage of methane: An experimental and computational investigation

Abstract The continuously increasing demand for natural gas as an available and clean energy source indicates an inevitable transition to develop more promising technologies such as solidified natural gas (SNG) storage. Herein, we present a comprehensive experimental and computational study of the utilization of sunflower oil as a renewable biomass source to design highly efficient promoters based on the properties of sodium dodecyl sulfate (SDS) for methane hydrate formation. The effect of sunflower oil-based promoters (SFOPs) on methane hydrate kinetics was investigated theoretically via molecular dynamics (MD) simulation and experimentally under both dynamic (stirred reactor) and static (in the presence of porous media) conditions. SFOP1 considerably reduced induction time and overall time of the hydrate formation process compared to SDS under both conditions. In addition, SFOP1 significantly enhanced the kinetic constant of hydrate formation by 13.5 times, 3.7 times, and 2.5 times compared to pure water, SFOP2, and SDS systems, respectively, (in dynamic conditions). Moreover, both SFOPs improved the number of moles of gas consumed up to 450 mM in dynamic and 200 mM in static conditions compared to the pure water test. In contrast to the SDS solution, no foam formation was observed in the solution containing SFOPs. The MD results revealed that the SFOPs increased the transfer of methane molecules to the growing hydrate surface, which lead to enhance the kinetics of methane hydrate formation. Besides, more hydrate was formed by the addition of SFOP1 because of the improvement in the hydrogen bonds between water-water molecules in comparison with SFOP2. These findings clearly confirm that sunflower oil can be used for the development of green and more efficient promoters than SDS for methane hydrate formation without foam generation during the process.