Kinetic Study of Methane Hydrate Formation by a Small-Molecule Peptide (Glutathione) and Its Complex System

The gas hydrate method for natural gas storage and transportation faces two major challenges: prolonged induction time and slow formation rate, which significantly limit its industrial application. Numerous chemical additives have been employed to improve hydrate formation kinetics. Among these, glutathione (GSH), a green, safe, and non-toxic small-molecule peptide, demonstrates significant potential for promoting methane hydrate formation. This study investigates the effects of varying GSH concentrations on hydrate nucleation induction time and gas storage capacity. The results reveal a dual-effect promotion mechanism dependent on concentration: low concentrations inhibit nucleation, while high concentrations promote it. Furthermore, by introducing amino acids to construct synergistic systems, a synergistic enhancement based on hydrophobic interactions between hydrophobic amino acids (particularly methionine) and GSH was discovered, significantly increasing gas storage capacity and shortening induction time. Subsequent investigations into composite systems combining thermodynamic promoters with GSH revealed that while co-incorporation with TBAB extended nucleation time, it guided the formation of highly porous hydrate structures. This significantly improved mass transfer, substantially increasing gas storage capacity. In simulated seawater environments, the "salting-out effect" at low salinity (1 wt%) enhanced GSH hydrophobic aggregation. This caused TBA+ ions to arrange more densely at the interface, increasing its order and accelerating nucleation. This study provides theoretical foundations and practical pathways for designing and applying green, efficient hydrate promoters.