Metal plate-based promotion on methane hydrate nucleation: Insights into the influence of metal type and surface properties.

[Display omitted] • Promotion effect of Mg, Al and Zn plate on methane hydrate nucleation is determined. • The synergistic promotion effect of acid condition and metal plate is proposed. • Two nucleation modes are observed in metal plate systems with pure water and acid condition. • Methane-liquid–metal interface plays a vital role on accelarating hydrate nucleation. • The promotion effect is closely related to surface topography and hydrophilicity of metal plate. Hydrate-based technologies hold significant promise in the fields of gas storage, water desalination and gas separation, but their application is restricted by the long induction time and high degree of randomness associated with hydrate nucleation. In this study, we conducted experimental investigations to access the influence of metal plates (Mg, Al and Zn) on methane hydrate nucleation under both pure water and acidic conditions. The results demonstrated that Mg plate exhibited the strongest promotion effect on methane hydrate nucleation. The presence of acid significantly accelerated hydrate nucleation in the Zn plate system, but conversely reduced the promotion effect of Al plate. In conjunction with the in-situ morphology evolution of hydrate nucleation, methane-liquid–metal interface was found to play a crucial role in the metal-induced promotion effect. Two nucleation modes were proposed accordingly: (i) in pure water, hydrate nucleation initiated exclusively at the methane-liquid–metal interface without extra nucleation site (Mode 1), and (ii) in acidic condition, hydrate nucleation occurred with evident multiple nucleation sites (Mode 2). Furthermore, SEM imaging, AFM and contact angle characterization revealed that the surface properties of metal plate (e.g., hydrophilicity and roughness) were the key factors in determining the effectiveness of the promotion effect. Liquid climbing upward along the metal plate surface was vital for metal plates to promote gas hydrate formation. Overall, this study provides new insights into hydrate nucleation promotion and suggests a straightforward way to enhance hydrate nucleation by modifying surface properties. [ABSTRACT FROM AUTHOR]