Regulatory Effect of Hydrophobic Amino Acid Side-Chain Structures on the Kinetics of Methane Hydrate Formation

Methane hydrate technology (MH) is pivotal for establishing natural gas as a bridge for energy transition. However, its slow formation kinetics present a core bottleneck hindering its commercial application. To address this challenge, this study focuses on the hydrophobicity and side-chain structures of amino acids (AAs) as a key research entry point. We systematically investigated the effects and underlying mechanisms of four hydrophobic AAs on the kinetic characteristics of MH formation. The results indicate that hydrophobic AAs can act as effective kinetic promoters, but their promoting effect is synergistically regulated by both concentration and side chain structure. In terms of gas storage performance, L-Phe achieves a maximum gas storage capacity of 143.02 V/V at 0.5 wt%, thanks to the strong hydrophobic property endowed by the benzene ring on its side chain. Regarding the formation rate, L-Met exhibited the best performance due to the unique modulation of hydrophobicity by its sulfur atom, simultaneously achieving the shortest induction time and T90 of 32.0 min and 203.5 min, respectively, at 0.7 wt%. Further analysis revealed that the concentration dependence of AAs presented two patterns: the induction time of L-Met and L-Trp showed a trend of “first increasing and then decreasing” with the increase of concentration, while that of L-Ile and L-Phe showed a trend of “first decreasing and then increasing”. These discrepancies can be reasonably explained by the synergistic effects between the hydrophobicity of the AAs and their specific side-chain chemical structures. It not only deepens the understanding of the action mechanism of AAs-based promoters but also provides a theoretical basis and design ideas for the future development of new MH promoters with targeted enhancement functions.