(70d) Molecular Dynamics Study of Carbon Dioxide Hydrate Decomposition

Gas hydrates represent an important class of crystalline solids that have relevance in fields such as the petrochemical industry, energy and the environment. Carbon dioxide hydrates provide a potential method of sequestering carbon dioxide (CO₂) in the ocean. Engineering efficient and effective methods to implement such a strategy requires an understanding of both the formation and decomposition mechanism of CO₂ hydrates. Molecular simulations provide an excellent method to study these questions at the microscopic level. In our work, we characterized the decomposition temperatures of carbon dioxide hydrates using extensive molecular dynamics simulations. The kinetics of decomposition is quantified by the temperature dependence of the hydrate-water interface velocity and the rate of CO₂ release upon hydrate decomposition. The effect of cage occupancy as well as the distribution of CO₂ molecules in the various cages of the sI hydrate structure on the decomposition of the hydrates was also studied. These studies form the basis upon which the effects of parameters like confinement and presence of salt on CO₂ hydrate decomposition can be investigated. The results provide a fundamental understanding of the decomposition kinetics of CO₂ hydrates which can aid kinetic experiments and theoretical models used to study and interpret hydrate decomposition in ocean.