(744b) Nucleation of Gas Hydrates in Interfacial Systems

Gas hydrates are solid crystalline structures formed when gases such as methane, ethane and carbon dioxide come in contact with water at low temperatures and high pressures. Hydrates remain a challenging flow assurance problem in the oil and gas industry. Recently, hydrates have also emerged as potential source of energy, route for carbon dioxide sequestration, alternative technology for water desalination and mode of gas transportation. The wide and promising applications in gas hydrates have renewed interest in understanding the molecular processes driving their formation, and stability. To this end, in our research, we use large-scale molecular dynamics simulations to probe the nucleation and growth of methane and tetrahydrofuran (THF) hydrates in interfacial environments. Specifically we investigate the effects of surface chemistry on hydrate nucleation by simulating solutions of methane/THF in water near hydrophobic and hydrophilic surfaces in hydrate forming conditions. We find that in case of methane at high concentration, the aggregation of methane molecules is promoted by the hydrophobic surface and inhibits hydrate formation due to the reduced concentration of methane in water. On the other hand no such effect is observed for the hydrophilic surfaces. In contrast, THF displays no preference to the surface and rapid nucleation is observed in both the systems. We conclude that for molecules with high solubility in water and for surfaces lacking any templating ability for hydrates, the surface chemistry does not affect hydrate nucleation.