Molecular dynamics simulation for surface melting and self-preservation effect of methane hydrate  

作　　者：DING LiYing GENG ChunYu ZHAO YueHong HE XianFeng WEN Hao 

机构地区：[1]Key Laboratory of Multi-phase Reaction,Institute of Process Engineering,Chinese Academy of Sciences,Beijing 100080,China [2]Graduate University of Chinese Academy of Sciences,Beijing 100049,China

出　　处：《Science China Chemistry》2008年第7期651-660,共10页中国科学（化学英文版）

基　　金：Supported by the National Natural Science Foundation of China (Grant No. 20221603)

摘　　要：The surface melting process of structure sI methane hydrate is simulated at T = 240, 260, 280, and 300 K using NVT molecular dynamics method. The simulation results show that a quasi-liquid layer will be formed during the melting process. The density distribution, translation, orientation, and dynamic properties of water molecules in the quasi-liquid layer are calculated as a function of the distance normal to the interface, which indicates the performance of quasi-liquid layer exhibits a continuous change from crystal-like to liquid-like. The quasi-liquid layer plays as a resistance of mass transfer restraining the diffusion of water and methane molecules during the melting process. The resistance of quasi-liquid layer will restrain methane molecules diffuse from hydrate phase to gas phase and slow the melting process, which can be considered as a possible mechanism of self-preservation effect. The performance of quasi-liquid layer is more crystal-like when the temperature is lower than the melt- ing-point of water, which will exhibit an obvious self-preservation. The self-preservation will weaken while the temperature is higher than the melting-point of water because of the liquid-like performance of the quasi-liquid layer.The surface melting process of structure sI methane hydrate is simulated at T = 240, 260, 280, and 300 K using NVT molecular dynamics method. The simulation results show that a quasi-liquid layer will be formed during the melting process. The density distribution, translation, orientation, and dynamic properties of water molecules in the quasi-liquid layer are calculated as a function of the distance normal to the interface, which indicates the performance of quasi-liquid layer exhibits a continuous change from crystal-like to liquid-like. The quasi-liquid layer plays as a resistance of mass transfer restraining the diffusion of water and methane molecules during the melting process. The resistance of quasi-liquid layer will restrain methane molecules diffuse from hydrate phase to gas phase and slow the melting process, which can be considered as a possible mechanism of self-preservation effect. The performance of quasi-liquid layer is more crystal-like when the temperature is lower than the melting-point of water, which will exhibit an obvious self-preservation. The self-preservation will weaken while the temperature is higher than the melting-point of water because of the liquid-like performance of the quasi-liquid layer.

关 键 词：gas HYDRATE surface MELTING SELF-PRESERVATION EFFECT MOLECULAR dynamics 

分 类 号：O621.2[理学—有机化学]