(728d) Study of the Thermodynamics and Kinetics of Carbon Dioxide Hydrate Formation and Dissociation

In recent years, the need for energy sources has drastically risen while ever-increasing levels of atmospheric carbon dioxide (CO2) are of urgent concern. Therefore, CO2 hydrates are of interest for their carbon storage potential to limit CO2 emissions. CO2 sequestration could be performed in naturally occurring methane hydrate reserves in marine and permafrost environments. As CO2 hydrates are thermodynamically and kinetically more stable than methane hydrates, this exchange process provides a potential pathway to recover methane coupled with CO2 sequestration. During this study, a small volume (~79 mL) reactor was built to monitor the conditions of CO2 hydrates as they formed in 12-15 mL of deionized water, salt water solution, or sodium dodecyl sulfate (SDS) solution. For each trial, the reactor was filled with solution at room temperature (23-29°C) and then pressurized to 450-475 psig before being place in a 2°C cooling bath. Over a minimum of four days, system pressure and temperature were continuously recorded. For half of the experiments, ~16 mL of the reactor was filled with sand to simulate ocean floor conditions. As hydrate formation is exothermic, temperature spikes confirmed that CO2 hydrates had formed. Hydrate formation was further validated by significant changes in the pressure vs time slope after these temperature spikes, as gas entered the hydrate phase at a faster rate. Formation results indicate that the presence of sand inhibited the conversion of gas into gas hydrates. In addition, hydrate formation in salt water resulted in the longest induction time. Dissociation results were able to verify predicted hydrate equilibrium, as well as show that equilibrium conditions are not significantly affected by SDS. Overall, these results suggest that techniques to encourage hydrate formation would benefit this approach to large scale marine CO2 sequestration.