CO2 Hydrate Formation and Dissociation Kinetics in Silica Sand Using Amino Acid Additives: Experimental Investigations and Implications for Carbon Sequestration

Storing carbon dioxide (CO2) as a hydrate in stratigraphic sediments is considered one of the most effective methods for reducing CO2 emissions and preventing global warming. However, the characteristics of CO2 hydrate formation/dissociation in marine settings can significantly affect the storage process. This study investigates CO2 hydrate formation/dissociation in silica sand porous media (particles of 400 μm) at reservoir conditions of 276.2 K and 3.3 MPa. For the first time, we conducted a comparative study to understand the efficacy of different hydrophobic amino acids for promoting CO2 hydrate formation in sediments. We evaluated the potential of three amino acid additives, l-leucine, l-tryptophan, and l-methionine, for sequestering carbon dioxide by forming CO2 hydrates in subsea deposits. Experiments were performed at two different concentrations of amino acids in both nonsaline and saline (3.5 wt % NaCl solution) conditions to mimic natural environments. Critical parameters such as gas consumption, uptake rate, and induction time were assessed to determine the effectiveness of these additives in promoting CO2 hydrate formation. It was observed that 0.2 wt % l-tryptophan exhibited the highest CO2 uptake, averaging 99.36 ± 2.93 mmol/mol H2O in nonsaline conditions. In contrast, 0.2 wt % l-methionine showed the least uptake in saline conditions, with an average of 22.41 ± 0.93 mmol/mol H2O. Salinity had a dominant effect at 0.2 wt %, but increasing the concentration to 1.0 wt % bypassed the influence of NaCl, with l-leucine and l-tryptophan showing favorable gas uptakes of 81.57 ± 0.16 and 63.71 ± 3.75 mmol/mol H2O, respectively. For nonsaline conditions, l-tryptophan exhibited the highest effectiveness, followed by l-methionine and l-leucine. In saline environments, l-leucine and l-tryptophan significantly promoted CO2 hydrate formation at 1.0 wt %, while l-methionine did not show any characteristic promotion effect. Salt presence significantly affects the hydrate dissociation, while amino acids have a more prominent impact on hydrate dissociation in the absence of salt.