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 hydratein stratigraphicsediments is considered one of the most effective methods for reducingCO(2) emissions and preventing global warming. However, thecharacteristics of CO2 hydrate formation/dissociation inmarine settings can significantly affect the storage process. Thisstudy investigates CO2 hydrate formation/dissociation insilica sand porous media (particles of 400 & mu;m) at reservoirconditions of 276.2 K and 3.3 MPa. For the first time, we conducteda comparative study to understand the efficacy of different hydrophobicamino 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 sequesteringcarbon dioxide by forming CO2 hydrates in subsea deposits.Experiments were performed at two different concentrations of aminoacids in both nonsaline and saline (3.5 wt % NaCl solution) conditionsto mimic natural environments. Critical parameters such as gas consumption,uptake rate, and induction time were assessed to determine the effectivenessof these additives in promoting CO2 hydrate formation.It was observed that 0.2 wt % l-tryptophan exhibited thehighest CO2 uptake, averaging 99.36 & PLUSMN; 2.93 mmol/molH(2)O in nonsaline conditions. In contrast, 0.2 wt % l-methionine showed the least uptake in saline conditions, withan average of 22.41 & PLUSMN; 0.93 mmol/mol H2O. Salinityhad a dominant effect at 0.2 wt %, but increasing the concentrationto 1.0 wt % bypassed the influence of NaCl, with l-leucineand l-tryptophan showing favorable gas uptakes of 81.57 & PLUSMN;0.16 and 63.71 & PLUSMN; 3.75 mmol/mol H2O, respectively.For nonsaline conditions, l-tryptophan exhibited the highesteffectiveness, followed by l-methionine and l-leucine.In saline environments, l-leucine and l-tryptophansignificantly promoted CO2 hydrate formation at 1.0 wt%, while l-methionine did not show any characteristic promotioneffect. Salt presence significantly affects the hydrate dissociation,while amino acids have a more prominent impact on hydrate dissociationin the absence of salt.