Molecular Insights into the Microscopic Behavior of CO<sub>2</sub> Hydrates in Oceanic Sediments: Implications for Carbon Sequestration
Fengyi Mi, Wei Li, Jiangtao Pang, Othonas A. Moultos, Fulong Ning, Thijs J. H. Vlugt
Abstract
High Resolution Image Download MS PowerPoint Slide Knowledge of the microscopic behavior of CO 2 hydrates in oceanic sediments is crucial to evaluate the efficiency and stability of hydrate-based CO 2 sequestration in oceans. Here, systematic molecular dynamics simulations are executed to investigate the growth and dissociation of CO 2 hydrates, and the mechanical instability of CO 2 hydrate-Illite interface in the brine-urea-Illite system. Simulation results show that the CO 2 hydrate growth is jointly affected by the confined space, Illite surface properties, and presence of urea. Specifically, the interfacial H 2 O and the ion layer on the Illite surface hinder the growth of CO 2 hydrate crystals toward Illite surfaces. Urea molecules can bind salt ions and increase CO 2 concentrations in the water, thus kinetically promoting CO 2 hydrate growth. The dissociation of the CO 2 hydrate is affected by Illite surface properties and the CO 2 hydrate structure. CO 2 hydrate starts from the regions where hydrate particles are minimally in contact and extends on both sides. The mechanical tension and compression of the CO 2 hydrate-Illite interface exhibit nonlinear characteristics by changing the hydrogen bonds and the CO 2 hydrate structure. The molecular insight into the microscopic behavior of CO 2 hydrates in the brine-urea-Illite system contributes to a broader understanding of hydrate-based CO 2 sequestration.