Growth Kinetics and Porous Structure of Surfactant-Promoted Gas Hydrate

Area of Science:

• Chemical Engineering
• Materials Science
• Physical Chemistry

Background:

• Surfactants are known gas hydrate promoters, but their mechanisms remain unclear.
• Understanding these mechanisms is crucial for gas hydrate applications like storage, separation, and desalination.

Purpose of the Study:

• To investigate the growth and porous structure of surfactant-promoted methane hydrate.
• To elucidate the promotion mechanisms of surfactants at the water/gas interface.

Main Methods:

• Optical microscopy and Raman imaging were used to observe methane hydrate growth in glass capillaries.
• Analysis covered scales from molecular (crystal structure) to macroscale (conversion rates, porosity).

Main Results:

• Hollow methane hydrate crystals form and create a porous medium.
• A significant increase in conversion rate was observed, linked to incorporated methane microbubbles.
• Anionic surfactants sodium dodecyl sulfate (SDS) and dioctylsulfosuccinate sodium (AOT) were compared.

Conclusions:

• AOT offers faster but limited conversion, suitable for continuous flow; SDS provides slower, more extensive conversion, ideal for gas storage.
• Surfactants do not affect methane cage filling in structure I methane hydrate.
• The study provides unprecedented insights into surfactant-mediated gas hydrate formation across multiple scales.