Enhanced methane hydrate formation using a newly synthesized biosurfactant: Application to solidified gas storage

Surfactants are considered the most influential promoters for accelerating the formation of gas hydrates in gas storage applications. However, their promotion mechanism remains unclear, and the formation of foam during the hydrate dissociation step severely limits hydrate-based gas storage technology. Oleic acid was used as a renewable biomass source in this study to develop a novel biosurfactant capable of enhancing methane hydrate formation. Oleic acid-based promoter (OAP) significantly improved kinetics of methane hydrate formation, and enhanced growth of hydrate crystals. A maximum conversion of 81 % and storage capacity of ∼151 v/v were achieved in a solution containing 1000 ppm OAP at 9 MPa. Additionally, OAP showed good promotion activity at a lower driving force (7 MPa), resulting in conversion and storage capacity 4.2 times greater than pure water. Moreover, molecular dynamics simulations revealed that the primary mechanism action of OAP is to increase the solubility of methane in an aqueous solution by forming promoter micelles. A gas release simulation for sodium dodecyl sulfate (SDS) solution generated significant foam, whereas no foam formed when OAP was present. The obtained findings are useful for developing efficient biosurfactants based on vegetable oils and can shed light on the promotion mechanism of promoters.