Influence of amino acids on gas hydrate formation and dissociation kinetics using flue gas (CO2 + N2 mixture) in silica sand under saline/non-saline conditions for CO2 sequestration

Carbon dioxide (CO2) emissions contribute significantly to global warming, driving interest in carbon capture and storage (CCS) strategies. One promising approach involves injecting flue gas (CO2 + N2) into marine sediments to form hydrates, facilitating CO2 storage. However, understanding the kinetics of hydrate formation and dissociation, especially under varying salinity conditions, remains crucial. In this study, we investigate these dynamics under isochoric and isothermal conditions, using the gas mixture of 25% CO2/75% N2 and addition of three different amino acids (L-leucine, L-methionine, L-tryptophan) at 1.0 wt% to enhance hydrate formation. Our findings reveal that L-leucine significantly accelerates hydrate kinetics, doubling hydrate yield compared to pure water, both in saline and non-saline conditions. Moreover, pressure driving force exerted a noticeable influence on gas uptake kinetics, with higher driving force accelerating the process. Morphological observations indicate hydrate formation within and above sediments, suggesting potential for practical application. Interestingly, CO2 selectivity within hydrate cages decreases with increased pressure driving force, attributed to heightened N2 dissolution in water and CO2-N2 competition for hydrate cages. Gas chromatographic analysis confirms the preferential selectivity of CO2 in larger cages, with hydrate phase gas doubling compared to feed gas. The introduction of salinity (3.5 wt% NaCl) slightly decreases overall hydrate yield. Additionally, hydrate dissociation studies highlight L-leucine's potential to slow gas release, enhancing its suitability for hydrate-based CO2 capture and sequestration. These findings underscore the scientific significance of understanding hydrate kinetics and salinity effects in advancing hydrate based CCS technology.