Concentration-Dependent Promotion Effect of Ethylene Oxide on CO 2 Hydrate Formation: Insights from Molecular Dynamics Simulations

The inherently slow kinetics of hydrate formation significantly constrain the practical application of hydrate-based technologies in fields such as carbon capture and storage (CCS). Chemical promoters offer a promising solution to enhance the rate of hydrate nucleation and growth. This study employed molecular dynamics simulations to investigate the molecular-level influence mechanisms of varying ethylene oxide (EO) concentrations on CO2 hydrate formation. The findings indicate that EO accelerates hydrate formation by enhancing water molecule diffusion and promoting the formation of tetrahedral structures. However, this promotional effect is strongly concentration dependent: at low concentrations, EO effectively shortens the induction period and enhances CO2 hydrate cage yield; at excessively high concentrations, EO competes with CO2 for water molecules, leading to a prolonged nucleation induction time, a decline in CO2 hydrate cages, and a concomitant rise in EO hydrate cage formation. The results indicate that approximately 12 wt % is the optimal EO concentration for promoting CO2 hydrate formation, providing theoretical insights into the development and dosage optimization of water-soluble thermodynamic promoters.