Micellization effects in surfactant-enhanced gas hydrate formation for efficient solidified methane storage

Gas hydrate-based methane storage offers a promising alternative to traditional methods for natural gas storage. It leverages the unique properties of gas hydrates to achieve high storage capacity under relatively mild conditions. However, its implementation is limited by slow formation rates and insufficient gas absorption. Surfactants have emerged as key promoters to enhance hydrate formation due to their ability to influence the interfacial properties of water and gas. Previous studies have reported conflicting results regarding the precise role of micellization in promoting hydrate formation. To address these discrepancies, this study employs molecular dynamics simulations to provide new insights into micellization theory. Thirteen surfactants, categorized as cationic, anionic, and non-ionic, were systematically analyzed based on their molecular structures and head group chemistries. The results reveal that micellization is highly surfactant-dependent, with double-chain and branched anionic surfactants exhibiting the highest propensity for micelle formation, while linear surfactants show limited micellization. Notably, commonly used surfactants like sodium dodecyl sulfate do not form micelles under hydrate conditions, suggesting that micellization is not the primary mechanism driving hydrate promotion. Instead, the promotion mechanism is attributed to a combination of factors, including hydrogen bonding, the iceberg effect, and the formation of semi-cage structures around surfactant molecules. Surfactants with an optimal balance of hydrophobic and hydrophilic groups create a favorable environment for hydrate nucleation and growth. They achieve this by stabilizing water structures and reducing mass transfer resistance. These findings provide critical molecular-level insights into surfactant behavior, offering a direction for designing effective hydrate promoters. This research not only advances the understanding of surfactant-mediated hydrate formation but also paves the way for optimizing methane storage and carbon capture technologies based on gas hydrates.