聚乙烯唑啉作用下甲烷水合物分解的分子动力学模拟

利用分子动力学模拟系统研究了不同质量浓度下(1.25%、2.50%、6.06%)聚乙烯唑啉(PEtO)对甲烷水合物的分解作用. 模拟体系为甲烷水合物2′2′2的超胞和聚合物对接体系. 模拟发现水分子间氢键构架的水合物笼型结构在PEtO的作用下出现扭曲, 最终导致水合物笼型结构完全坍塌. 通过氧原子径向分布函数、均方位移以及扩散系数比较不同浓度PEtO的作用, 证实在一定浓度范围内, PEtO的浓度越高, 其水合物分解作用越强. 此外, PEtO 具有一定的可生物降解性. PEtO 对水合物的作用为: PEtO 吸附在水合物表面, 其中的酰胺基(N―C＝O)与成笼的水分子形成氢键, 破坏邻近的笼形结构, 令水合物分解; PEtO不断分解表面的水合物, 直到水合物笼完全分解.

Molecular Dynamics Simulation of CH4 Hydrate Decomposition in the Presence of Poly(2-ethyl-2-oxazoline)

Molecular dynamics simulations were carried out to study the decomposition of CH4 hydrate in the presence of poly(2-ethyl-2-oxazoline) (PEtO) at different concentrations, including 1.25% , 2.50%, and 6.06% (w, mass fraction). The simulation system was composed of a CH4 hydrate crystal and PEtO, which contained a 2×2×2 supercell of CH4 hydrate crystal and PEtO polymer. System configurations showed that hydrogen bonding networks between water molecules making up the main framework of the hydrate cages were distorted in the presence of the PEtO polymer. Final configurations in all of the systems were completely collapsed. Radial distribution functions of the oxygen atoms, mean square displacements, and diffusion coefficients of water molecules were applied to compare the effect of different PEtO concentrations on the CH4 hydrate. Within a certain concentration range, higher concentrations led to a better inhibition effect. It was confirmed that PEtO is a type of prospective low dosage inhibitor with biodegradability. The decomposition mechanism involves the absorption of the PEtO polymer onto the surface of the hydrate crystal, with its active functional group (N ― C=O) forming hydrogen bonds with water molecules in the hydrate and decomposing the hydrate surface. PEtO continued to decompose the surface layer of hydrate, resulting ultimately in the collapse of the hydrate cages.