Molecular insights into the effects of lignin on methane hydrate formation in clay nanopores

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

“…The spherical nanobubble in the nanopore is situated in the middle region of the nanopore and remains detached from the clay surface, whereas the spherical nanobubble in the bulk solution is far away from the nanopore (Figure A_II–III). Glucose molecules adsorb on CH 4 nanobubble surfaces, and the presence of six-membered rings adsorbing onto these surfaces has been observed in previous MD studies (Figure A_III). At the beginning of the simulation, several hydrate cages form in the middle region of the nanopore and the bulk solution but disappear soon, indicating that these sporadic hydrate cages are unstable and easily decompose (Video S1 and Figure A_II,III).…”

“…Hydrate cages are shown as sticks in various colors (green for 5 12 , blue for 5 12 6 2 , red for 5 12 6 3 , orange for 5 12 6 4 , cyan for 4 1 5 10 6 2 , purple for 4 1 5 10 6 3 , and pink for 4 1 5 10 6 4 ). nanobubble surfaces, and the presence of six-membered rings adsorbing onto these surfaces has been observed in previous MD studies 58 (Figure 4A_III). At the beginning of the simulation, several hydrate cages form in the middle region of the nanopore and the bulk solution but disappear soon, indicating that these sporadic hydrate cages are unstable and easily decompose (Video S1 and Figure 4A_II,III).…”

“…50−52 Molecular dynamics (MD) simulations have been often employed to investigate the microscopic behavior of gas hydrates from the molecular scale. 53−57 Based on MD simulation, some studies had reported that lignin, 58 protein, 47 humic acid, 59 fatty acid, 60 amino acid, 61 and other organic matters 62,63 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.…”

“…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.…”