Molecular Insights into the Impacts of Calcite Nanoparticles on Methane Hydrate Formation

Abstract

Despite the potential broad utility of nanoparticles in hydrate-related fields, there remains a paucity of studies on the impacts of nanoparticles on gas hydrate formation. In this study, massive microsecond molecular dynamics simulations were performed to investigate the roles of calcite nanoparticles on the formation processes of methane hydrate. Our results indicate that calcite nanoparticles prefer to be in the water phase close to the water/gas interface. They inhibit methane hydrate nucleation because a layer of bound water with a thickness of 0.75 nm forms around each nanoparticle which results in an extremely low methane concentration region. Thus, methane hydrate nucleates away from the nanoparticle, and no clear connection between the nucleated hydrate and the nanoparticle is observed. The nanoparticles associate easily, and a water layer with a thickness of 1.15 nm forms between the associated nanoparticles. Moreover, methane hydrate growth is not influenced by calcite nanoparticles until the growth front approaches the bound water around the nanoparticle. These molecular insights of the impacts of calcite nanoparticles on methane hydrate formation are beneficial for the application of nanoparticles in hydrate mining and hydrate-related technologies.

Molecular Study on Carbon Dioxide Hydrate Formation in Salty Water

“…The F 4φ is defined as F 4φ = ⟨cos­(3φ)⟩ with average values of −0.4, −0.04, and 0.7 for ice, liquid water, and hydrate, where φ is the torsion angle between two adjacent water molecules . The number of cages was analyzed by using the FSICA code, which can identify all the face-saturated hydrate cages associated with hydrate nucleation and growth. − The growth rate of CO 2 hydrate was calculated as the rate of change of water molecules in the hydrate phase per unit cross-sectional area over time, similar to the procedure utilized in our previous works. , The sampling was performed over 50–150 ns. Ions incorporated in the hydrate phase were defined as those whose F 4φ of the first hydration shell (FHS) water was greater than 0.5.…”

Effect of Glucose on CH4 Hydrate Formation in Clay Nanopores and Bulk Solution: Insights from Microsecond Molecular Dynamics Simulations

“…Park and coworkers observed that CH 4 hydrate solids can stably intercalate within montmorillonite interlayers under conditions of lower pressure and higher temperature, suggesting that a portion of such clay mineral surface actively involved in promoting CH 4 hydrate formation . Recently, Ren et al reported that montmorillonite shortens the induction time of gas hydrate formation by providing additional nucleation sites but retards the growth kinetics of gas hydrate due to hindered mass transfer. , Several experimental studies have found that the phase equilibrium of CH 4 hydrate is inhibited in porous media composed of solid particles. − Our previous study revealed that clay surfaces affect gas hydrate formation by changing the concentration of guest molecules and ions via the adsorption of water molecules, ions, and guest molecules. , On the other hand, the abundant organic matter in hydrate reservoirs will also affect the formation behavior of gas hydrates. , Liu and coworkers found that organic matter can kinetically promote gas hydrate formation by enhancing gas–water contact, and this effect was further enhanced by sulfur-containing acid-dissolvable organic matters. , Some studies revealed that organic matter molecules inhibit the formation of gas hydrates by association with water molecules. , It is worth noting that recent studies have observed that organic matter and clay minerals have a synergistic effect on the formation of gas hydrates, which significantly shortens the induction time for gas hydrate formation. − Molecular dynamics (MD) simulations have been often employed to investigate the microscopic behavior of gas hydrates from the molecular scale. − Based on MD simulation, some studies had reported that lignin, protein, humic acid, fatty acid, amino acid, and other organic matters , exhibit different effects on the formation and growth of gas hydrate. Furthermore, some MD simulation results found that clay mineral surfaces can repel organic matter or form organo-mineral complexes, significantly influencing the wettability of the clay surface. , The interaction between organic matter and clay surfaces complicates the formation processes of gas hydrates.…”

Investigation of the Influence Mechanism of CO2 Hydrate Formation in Seawater Systems in the Presence of Solid Promoters by Combining In Situ Raman Analysis with Macroscopic Experiments

“…22,23 Calcite nanoparticles in the aqueous phase are close to the water/air interface, and a layer of bound water is formed around each nanoparticle, thereby inhibiting the nucleation of methane hydrate. 24 The fundamental process underlying hydrate formation involves the rearrangement of water molecules under specific conditions as they transform into hydrates. To gain insights into how nanoparticles affect hydrate formation, it is necessary to investigate their impact on the water molecule arrangement.…”