Investigation of Kinetics of Formation of Methane plus Propane Hydrates by Molecular Dynamics Method in the Presence of Hydrate Seed and Sea Salt

In the presented work we studied the process of nucleation and growth of methane and propane gas hydrate from a homogeneous solution by means of molecular dynamics. The aim is to assess the effect of hydrate seed on the growth rate and structure of the resulting hydrate in the presence of sea salt. This process was characterized via calculation of the number of long-lived hydrogen bonds and amount of hydrate and hydrate-like cavities, as well as the order parameter of the intermolecular torsion angles. It is shown that the kinetics of hydrate formation do not differ much in the cases of pure water and seawater. A seed crystal of hydrate on the contrary, not only increases the hydrate growth rate, but also makes the resulting structure more consistent with the cubic structure II hydrate.

Automated summary

In this study, we used molecular dynamics to investigate the nucleation and growth process of methane and propane gas hydrate from a homogeneous solution. Our aim was to understand the impact of hydrate seed on the growth rate and structure of the resulting hydrate in the presence of sea salt. We characterized the process by calculating the number of long-lived hydrogen bonds, the amount of hydrate and hydrate-like cavities, and the order parameter of intermolecular torsion angles. The results showed that the kinetics of hydrate formation were similar in pure water and seawater. However, a seed crystal of hydrate not only increased the growth rate, but also resulted in a structure closer to cubic structure II hydrate.