Unraveling the Microscopic Influence Mechanism of H ₂ S on Methane Hydrate Formation via Molecular Simulation Techniques

Sour natural gas holds significant economic value, but its pipeline transportation is challenged by H₂S accelerating natural gas hydrate nucleation/growth and exacerbating pipeline blockages under low temperature. Through molecular dynamics simulations, our study reveals that H₂S promotes nanobubble dissolution and increases local guest molecule concentration, thereby shortening induction time and accelerating nucleation. However, high H₂S concentrations inhibit stable cage growth by disrupting water's hydrogen-bond network, causing the decomposition of unstable/large cages. Simultaneously, H₂S alters hydrate cage composition: reducing H₂S unstable/large cages while significantly increasing stable 5¹²6² cages, thus promoting Structure I (sI) hydrate formation. Mechanistically, H₂S acts as a hydrogen atom donor to form hydrogen-bond-like interactions with water, stabilizing the H-bond network and repairing lattice defects─collectively accelerating hydrate nucleation and growth. These findings provide a fundamental understanding that could advance research on sour natural gas transportation.