Intensified Carbon Dioxide Hydrate Formation Kinetics in a Simulated Subsea Sediment: Application in Carbon Capture and Sequestration

To achieve the United Nations Climate Change Conference (COP-26) targets of net zero carbon emissions, hydrate-based carbon dioxide (CO2) capture and sequestration (CCS) can be considered one of the potential sustainable technologies. However, the sluggish kinetics of CO2 hydrate formation in the saline subsea environment and the nonecofriendly nature of the existing additives (kinetic promoters) are the major challenges. Therefore, to intensify the kinetics, the performance of the biocompatible hydrophobic amino acid Lleucine for CO2 hydrate formation/dissociation was evaluated using the simulated subsea sediment of silica sand. Experiments were performed in saline (3.0 wt % NaCl) and nonsaline environments with L-leucine (0.1-1.0 wt %) at 3.2 +/- 0.2 MPa pressure and 274.5 +/- 0.2 K temperature. With the addition of 0.5 wt % L-leucine to freshwater, water-to-hydrate conversion of 73.01 +/- 4.96% (44.08 +/- 2.95% gas-to-hydrate conversion) was achieved with a rate of gas uptake of 4.25 +/- 0.39 mmol/min, which is similar to 10 times higher compared to the baseline (no promoter). Though salinity significantly reduced the hydrate formation kinetics, the addition of 1.0 wt % L-leucine intensified the rate of CO2 uptake to 2.32 +/- 0.319 mmol/min from 0.55 +/- 0.033 mmol/min in saline water baseline. The enhanced kinetics reported in this work highlights the potential of engaging L-leucine in the hydrate-based CCS approach