Molecular dynamics simulation of the intercalation behaviors of methane hydrate in montmorillonite

Abstract

The formation and mechanism of CH4 hydrate intercalated in montmorillonite are investigated by molecular dynamics (MD) simulation. The formation process of CH4 hydrate in montmorillonite with 1 ~ 8 H2O layers is observed. In the montmorillonite, the "surface H2O" constructs the network by hydrogen bonds with the surface Si-O ring of clay, forming the surface cage. The "interlayer H2O" constructs the network by hydrogen bonds, forming the interlayer cage. CH4 molecules and their surrounding H2O molecules form clathrate hydrates. The cation of montmorillonite has a steric effect on constructing the network and destroying the balance of hydrogen bonds between the H2O molecules, distorting the cage of hydrate in clay. Therefore, the cages are irregular, which is unlike the ideal CH4 clathrate hydrates cage. The pore size of montmorillonite is another impact factor to the hydrate formation. It is quite easier to form CH4 hydrate nucleation in montmorillonite with large pore size than in montmorillonite with small pore. The MD work provides the constructive information to the investigation of the reservoir formation for natural gas hydrate (NGH) in sediments.

Effect of hydrophilic silica nanoparticles on hydrate formation: Insight from the experimental study

“…For the adsorbed water molecules on hydrophilic nano-SiO 2 surface, they would form hydrogen bonds with the hydroxyl group, which is stable against the influence of the hydrophobic methane molecules through the weak van der Waals force [29] . Indeed, molecular dynamic simulation showed that the water at the surface of clay could not be considered bulk-like and these water molecules constructed the network by hydrogen bonds with the surface Si-O ring of hydrophilic clay [45,46] . Therefore, the adsorbed water molecules aligned on the surface of the nanoparticles become difficult to re-arrange themselves to form a clathrate hydrate structure surrounding the CH 4 molecules.…”

Effect of electrolytes and soil minerals on nitrous oxide (N2O) hydrate formation kinetics

“…Electrolytes can reduce the chemical potential of hydrate-forming molecules (H 2 O and N 2 O) and enter open cavities of hydrate structures (Svartaas et al, 2000;Lamorena and Lee, 2008;Kyung et al, 2015). Additionally, their steric effects (construction/destruction) of the hydrogen-bond network among water molecules can distort the hydrate structure (Yan et al, 2014). Ultimately, for complex reasons, the driving force of hydrate nucleation and growth were depressed, and the formation kinetics for N 2 O hydrate slowed down in the presence of electrolytes.…”

“…It is known that the effects of soil minerals on hydrate formation kinetics are complex because many factors (e.g., surface area, pore size, intercalation of water molecules, and dissolved chemical species) can affect hydrate formation on the surfaces, and in the pores, of soil minerals (Lamorena and Lee, 2008;Yan et al, 2014). Table 3 shows the surface area, pore size, concentrations of dissolved cations, and solvation energy of each soil mineral.…”

Effect of Soil Solution pH during the Tetracycline Intercalation on the Structural Properties of a Dioctahedral Smectite: Microstructural Analysis

“…The montmorillonite layer structure can expand and contract its structures without crystallographic change. These expansions depend on the IS content (water/polar molecule) and the surrounding environment (relative humidity rate) [13][14][15][16][17].…”