Molecular dynamics study of the micro-mechanism of CO2 hydrate formation in the confined space of porous media

Abstract

Sequestration and storage of CO₂ in the form of hydrate is an effective strategy to reduce carbon dioxide emissions in the atmosphere. In this work, Molecular Dynamics simulation was employed to investigate the formation process of CO₂ hydrate in the confined space of graphene porous media by comparing to the pure water system with fully developed space. Results demonstrated that hydrate formation was facilitated in confined space of porous media. The incorporation of porous media and the existence of confined space prominently enhanced the heat and mass transfer characteristics, with the thermal conductivity along the formation direction reaching 2614.22 % of the pure water system. However, such porous media and structure simultaneously induced hydrate structural destabilization, including decomposition, band diffusion, and dislocation of hydrate cell. Notably, the existence of unstable hydrate cages promoted the rapid formation of hydrate. And this study also thoroughly elaborated distinct regulatory mechanisms between unstable non-empty and empty cages. Additionally, due to the superior adsorption effect of graphene on CO₂ molecules, the CO₂ molecular "bubble" reduced the impact from porous media on hydrate.