Molecular dynamics simulations on the inhibition of methane hydrates.

摘要

We study the effect of a specific hyperbranched poly(ester amide)s on the growth of the methane hydrate with atomistic molecular dynamics simulation. The growth of methane hydrates was modeled as a solid/liquid system containing a slab of hydrate crystallite and a liquid methane/water mixture. We modeled the effects of two versions of this molecular system, either the core structure (H400) or a full sized version molecule (H1500), to examine whether the molecular weight of inhibitors affect the growth of the hydrate. Radial distribution functions for carbon atoms of methane molecules are employed to examine the growth of crystal structures of the systems in the presence or absence of an inhibitor. In addition, the detailed processes of hydrate growth initiated by the crystallite in all systems are explored by examining the z-density profiles of the carbon and oxygen atoms of the methane and water molecules. The minimum change of entropy is estimated for both of the inhibited systems. These results show that the hydrate crystallite keeps growing in the presence of H400, while it dissociates when H1500 is present in the system. Thus the molecular size of the inhibitor plays a role controlling the hydrate formation.