Molecular Dynamics Simulation of Methane Hydrate Growth in the Presence of the Natural Product Pectin

Abstract

Molecular dynamics simulation was used to examine the growth of methane hydrate in the presence of natural product pectin at different concentrations, including the mass fractions 2.46% and 3.62%. Snapshots of the system configurations with time, radial distribution functions of the carbon atoms, and the total energy of the system were employed to characterize the effect of pectin on methane hydrate growth. Results indicated that pectin is a good inhibitor of methane hydrate. The higher the concentration of pectin is, the better the effect of inhibition is. The double-bonded oxygen atoms of pectin combine with hydrogen atoms of water, and the hydrogen atoms of hydroxyl in pectin combine with oxygen atoms of water through hydrogen bonds, which disturbed the further growth of the methane hydrate. The role of the pectin’s active groups in hydrogen bonds with water both as proton donor and as electron acceptor makes pectin have a better inhibitory effect on the growth of methane hydrate.

Inhibition of methane and natural gas hydrate formation by altering the structure of water with amino acids

“…3c ). In the presence of KHIs, the rate of CH 4 hydrate formation can be lowered, especially at the intermediate stage 32 33 . One unexpected result is the poor KHI efficiency of L-proline, which is the best THI of the tested amino acids.…”

“…However, it remains difficult to predict the kinetics of hydrate formation 9 , especially in the presence of KHIs, as it is a very complex and dynamic process. There have been numerous attempts to identify possible additives through molecular design and the testing of potential candidates 10 11 12 13 14 15 16 . More recently, the risk of environmental contamination has led to efforts to develop environmentally friendly additives.…”

Overview of Molecular Dynamics Simulation of Natural Gas Hydrate at Nanoscale

“…As can be seen from Figure 9, at the initial stage of simulation, methane gas accumulates around pectin, and the gas-liquid phase splits, forming a pectin layer between water molecules and guest molecules, increasing the mass transfer resistance, and resulting in difficult hydrate growth. At 20 ns, water molecules interact with pectin through hydrogen bonds, disrupting the hydrogen bond network between water molecules and hindering the further growth of gas hydrate (Figure 9(b), 20 ns enlarged figure) [113]. Zi et al conducted MD simulation to explore the role of asphaltenes in the formation of methane hydrate, and the results showed that the asphaltenes located at the gas-water interface promoted the formation of hydrates, while the asphaltenes in water had a slight inhibitory effect on the growth of hydrates [114].…”

“…Figure 9: Configurations of pectin at 0, 1, 2, 3, 4, 5, 10, and 20 ns.Where blue represents water molecules, blue dotted lines represent hydrogen bonds, green represents methane, and red represents pectin (from reference[113]). …”

Advances in coupling thermodynamics and kinetics studies of wax precipitation-deposition and hydrate nucleation-formation

“…Figure 12 (Color online) Comparison of adhesion forces between stainless steel surfaces and wax coated surfaces with and without AAs [118] 图 13 含蜡和AA3 体系的水合物颗粒图 [118] Figure 13 Image of a hydrate particle formed with wax and AA3 [118] 动力学 ( Figure 14 (Color online) Snapshot configurations of liquid-solid interface. (a) No pectin; (b) pectin: 2.46 wt%; (c) pectin: 3.62 wt% [119] 图 15 (网络版彩色)Gao [121] 蜡晶和水合物相互作用实验现象. (a) 有水合物存在时蜡晶在管内壁沉积; (b) 无水合物出现时也无蜡晶沉积 Figure 15 (Color online) Experimental phenomena of wax and hydrate interaction by Gao [121] .…”