Impact of acetamide, 1,2,4-triazole, and 1-dodecyl-2-pyrrolidinone on carbon dioxide hydrate growth: Application in carbon dioxide capture and sequestration

Gas hydrates have served as the focal point of research from a sustainable engineering perspective, due to their specific applications in diverse scientific areas including carbon dioxide (CO2) gas storage, carbon capture, and sequestration (CCS). However, improved kinetics of CO2 hydrate formation will render the development of technologies for CCS. In this context, it should be mentioned that under the seafloor, low temperature and high pressure prevail, which makes the sequestration of gaseous CO2 in the form of solid hydrates plausible. In this study, both formation and dissociation kinetics of CO2 hydrates have been investigated in the presence of aqueous solutions of three CO2-philic additives, namely, acetamide, 1,2,4-triazole, and non-ionic surfactant 1-dodecyl-2-pyrrolidinone (DDP) with varying concentrations (0.5, 1, 2, and 4 wt%) at 274.55 K and 3.6 MPa in a 1.4 L stirred tank reactor. These chemicals having high binding energies with CO2, draw the dissolved CO2 molecules towards the hydrate cages by strongly interacting with them. Moreover, DDP can enhance the rate of gas dissolution by lowering the surface tension at the gas-water interface and altering the contact angle. All the additives exhibited considerable improvements in gas uptake than pure water, with 0.5 wt% DDP showing the most substantial promoting effect as it increased the moles of CO2 uptake and water-to-hydrate conversion by 55%. Likewise, about a 28% rise in these metrics was observed with 0.5 wt% acetamide and 2 wt% of 1,2,4-triazole. Furthermore, a reduction of 80% was observed in t90 with 0.5 wt% of DDP. The positive impacts of DDP and acetamide were highest at a lower concentration of 0.5 wt%, signifying their economic feasibility. The dissociation studies conducted on the CO2 hydrates up to 293.15 K demonstrated high dissociation rates, thus faster CO2 recovery for further use. This study conclusively shows that the additives might be used as equitable kinetic promoters for the CO2 hydrate relevant to CCS.