CO<sub>2</sub> Hydrate Formation and Dissociation Kinetics in Silica Sand Using Amino Acid Additives: Experimental Investigations and Implications for Carbon Sequestration
Eti Pagar, Sai Kiran Burla, Vimal Kumar, Hari Prakash Veluswamy
Abstract
Storing carbon dioxide (CO 2 ) as a hydrate in stratigraphic sediments is considered one of the most effective methods for reducing CO 2 emissions and preventing global warming. However, the characteristics of CO 2 hydrate formation/dissociation in marine settings can significantly affect the storage process. This study investigates CO 2 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 CO 2 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 CO 2 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 CO 2 hydrate formation. It was observed that 0.2 wt % l -tryptophan exhibited the highest CO 2 uptake, averaging 99.36 ± 2.93 mmol/mol H 2 O 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 H 2 O. 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 H 2 O, 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 CO 2 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.