Molecular insights into the fast hydrate formation in active ice

Abstract

Molecular dynamics simulations were performed to study the microscopic working mechanism of fast hydrate formation from active ice. We successfully simulated the cyclic process of ice melt-hydrate formation-ice melt. The simulation results showed that active ice could significantly accelerate the formation of hydrates and exhibit high gas storage capacity. The oxygen atoms of the sulfate group in SDS formed hydrogen bonds with the hydrogen atoms of water molecules in the ice, destroying the orderly arranged structures of the ice surface. SDS also acted as a promoter to accelerate the mass transfer of guests in the liquid phase, thereby promoting the nucleation and growth of hydrates. The ordered structures of liquid phase formed by ice melting and the formation of cage-like structures facilitated by ice surface defects were beneficial to the nucleation and growth of hydrates. The formation of the hydrate shell accelerated the migration of the guests from the gas phase to the liquid phase. As the ice continued to melt, sufficient guests and water molecules ensured the stable growth of hydrates.