Ultrafast Formation of Carbon Dioxide Hydrate Foam for Carbon Sequestration

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We report ultrafast formation of carbon dioxide (CO₂) hydrate foam without the use of any conventional chemical promoters or mechanical agitation. Our 6× enhancement in the CO₂ sequestration rate (based on net gas consumption) results from the high flow rate sparging of CO₂ gas in water in an open system (constant gas inflow/outflow) in the presence of magnesium. This approach continuously renews the gas–water–hydrate interface, thereby increasing the growth rate. The CO₂ gas consumption rate (for hydrate foam formation) and foam composition (hydrate, CO₂ dissolved in water, trapped CO₂ gas) are experimentally quantified versus various parameters, including thermodynamic (pressure), CO₂ flow-related parameters (flow rate, duration), water composition, and quantity of magnesium. The maximum measured CO₂ sequestration rate (time-averaged) of 1276.5 g h^–1 L^–1 MPa^–1 is 6 times higher than the fastest reported instantaneous rate. Importantly, we show rapid foam formation with saltwater, which will greatly improve the techno-economics. We develop an analytical framework to evaluate the composition of foam. We discover that the reactor pressure is a key determinant of the sequestration rate under high flow rate conditions, with magnesium playing a catalytic role. Overall, such foams enable new approaches to transport and sequester CO₂ and benefit other applications that are hindered by notoriously sluggish hydrate formation.