Kinetics of methane hydrate formation in rhamnolipid solution

Abstract Solidified natural gas (SNG) offers a promising route for natural gas storage and transportation, but its practical application is hindered by slow hydrate formation kinetics and the environmental concerns of chemical surfactants. This study investigates the environmentally friendly biosurfactant rhamnolipid as a kinetic promoter for methane hydrate formation. Experiments were conducted in a 1000 mL reactor at 275.15 K and 6.5 MPa with rhamnolipid concentrations of 500–5000 ppm, and CSMGem confirmed the hydrates as structure I within the stability zone. Gas uptake, induction time, and storage capacity were measured and compared with SDS (300–3000 ppm), and mixed rhamnolipid–SDS systems were also evaluated. Rhamnolipid enhanced hydrate formation in a concentration‐dependent manner, with optimal performance at 3000 ppm: methane uptake of 0.95 mol and gas storage density of 33.91 v/v, corresponding to increases of 554.6% and 554.5% over pure water, respectively, and reaching ~19.7% of the theoretical maximum for sI hydrate (~172 v/v). At 5000 ppm, performance declined markedly (induction time: 300 min; uptake: 0.34 mol), attributed to micelle formation and increased viscosity. Morphological observations revealed fibrous growth at 1000 ppm and spike‐like crystals at 3000 ppm, driven by capillary transport. Mixed rhamnolipid–SDS systems exhibited antagonistic effects across all tested ratios, with reduced gas uptake and significant foaming. Overall, rhamnolipid is an efficient and sustainable alternative to synthetic surfactants for hydrate‐based gas storage, while its combined use with SDS is not recommended.