Microscopic insights into interface characteristics of methane hydrate dissociation under external stimulations and molecular defects

YL Zhang and ZN He and P Zhao and GM Xin and N Qin, COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS, 703, 135262 (2024).

DOI: 10.1016/j.colsurfa.2024.135262

Gas hydrate dissociation is crucial in both natural environments and industrial applications. Yet some critical micro interface characteristics within it were neglected before, which hinders understanding and regulating hydrate phase change and associated multiphase flows. Herein, a combination of molecular dynamics and density functional theory is utilized to compare the interface characteristics of methane hydrate dissociation under external stimulations and internal molecular defects. Results show that thermal stimulation alone can cause a metastable residual water film. It adheres to hydrate surface, acting as an interface mass transfer barrier for further dissociation, and can be weakened by alcohols. Electric fields can completely prevent metastable residual water film since they peel water molecules far away from the surface layer by layer. With electric field intensity rising, an "electric locking" effect is identified, which limits the movement of water and rebuilds a new hydrogen bond network. Moreover, an interesting transition from a flat to a curved gas-liquid interface is revealed. It can be fundamentally attributed to the stronger interaction between water molecules under electric fields, and macroscopically manifests as an increase in interfacial tension. In the presence of foreign gases, a corrosion-like process on hydrate surface is found to dominate the dissociation. Water molecule defects result in lower hydrate stability compared to methane molecule defects. Notably, water molecule defects beyond 10 % can cause an abnormal, non- progressive dissociation in bulk phase, which avoids the effects of surficial metastable water film.

Return to Publications page