Dual Promotional Effect of l-Tryptophan and 1,3-Dioxane on CO2Hydrate Kinetics in Seawater under Static/Unstatic Conditions for Carbon Capture and Storage Application

CO2hydrates hold promising applications, including as a medium for carbon storage in oceanic sediments, as a result of their high storage capacity. However, the presence of high salinity in sediments is likely to affect the CO2hydrate kinetics. To counter this challenge, the CO2hydrate formation, dissociation, and deep morphology have been investigated in seawater (SW) under static and non-static conditions. Moreover, the effect of a kinetic promoter [1000 ppm of l-tryptophan (l-tryp)] and a thermodynamic promoter (5 wt % 1,3-dioxane) and dual promotional effects of kinetic and thermodynamic promoters (1000 ppm of l-tryp + 5 wt % 1,3-dioxane) have also been studied. In situRaman spectroscopy was used to probe the real-time CO2dissolution in seawater in the presence of 1,3-dioxane. The CO2uptake in seawater for the static system was estimated to be in the following order (20 h): CO2(30.5 ± 5.0 mmol/mol) > CO2+ 1000 ppm of l-tryp (30 ± 1.20 mmol/mol) > CO2+ 1,3-dioxane + 1000 ppm of l-tryp (26.2 ± 7.1 mmol/mol) > CO2+ 1,3-dioxane (21.1 ± 6.1 mmol/mol). In comparison, for the non-static system, the CO2uptake in seawater was estimated to be in the following order (20 h): CO2+ 1000 ppm of l-tryp (67.8 ± 2.20 mmol/mol) > CO2+ 5 wt % 1,3-dioxane (49.3 ± 7.0 mmol/mol) > CO2+ 5 wt % 1,3-dioxane + 1000 ppm of l-tryp (42.9 ± 4.8 mmol/mol) > CO2(39.5 ± 4.1 mmol/mol).