In this study, the kinetics of flue gas hydrate formation in bulk water in the presence of selected amino acids and surfactants are investigated. Four amino acids (3000 ppm) are selected based on different hydropathy index. Constant-ramping and isothermal experiments at 120 bar pressure and 1 °C temperature are carried out to compare their hydrate promotion capabilities with surfactant sodium dodecyl sulfate (SDS) (500–3000 ppm) and water. Based on experimental results, we report the correlation between hydrate promotion capability of amino acids and their hydrophobicity. Hydrophobic amino acids show stronger flue gas hydrate promotion capability than water and hydrophilic amino acids. We discuss the controlling mechanisms to differentiate between promoters and inhibitors’ roles among the amino acids. Between 2000–3000 ppm concentrations, hydrophobic amino acids have near similar promotion capabilities as SDS. This research highlights the potential use of amino acids as promoters or inhibitors for various applications.

Geological sequestration of CO₂-rich gas as a CO₂ capture and storage technique has a lower technical and cost barrier compared to industrial scale-up. In this study, we have proposed CO₂ capture and storage via hydrate in geological formation within the hydrate stability zone as a novel technique to contribute to global warming mitigation strategies, including carbon capture, utilization, and storage (CCUS) and to prevent vast methane release into the atmosphere caused by hydrate melting. We have attempted to enhance total gas uptake and CO₂ capture efficiency in hydrate in the presence of kinetic promoters while using diluted CO₂ gas (CO₂-N₂ mixture). Experiments are performed using unfrozen sands within hydrate stability zone condition and in the presence of low dosage surfactant and amino acids. Hydrate formation parameters, including sub-cooling temperature, induction time, total gas uptake, and split fraction, are calculated during the single-step formation and dissociation process. The effect of sands with varying particle sizes (160–630 µm, 1400–5000 µm), low dosage promoter (500–3000 ppm) and CO₂ concentration in feed gas (20–30 mol%) on formation kinetic parameters was investigated. Enhanced formation kinetics are observed in the presence of surfactant (1000–3000 ppm) and hydrophobic amino acids (3000 ppm) at 120 bar and 1 ℃ experimental conditions. We report induction time in the range of 7–170 min and CO₂ split fraction (0.60–0.90) in hydrate for 120 bar initial injection pressure. CO₂ split fraction can be enhanced by reducing sand particle size or increasing the CO₂ mol% in incoming feed gas at given injection pressure. This study also reports that formation kinetics in a porous medium are influenced by hydrate morphology. Hydrate morphology influences gas and water migration within sediments and controls pore space or particle surface correlation with the formation kinetics within coarse sediments. This investigation demonstrates the potential application of bio-friendly amino acids as promoters to enhance CO₂ capture and storage within hydrate. Sufficient contact time at gas-liquid interface and higher CO₂ separation efficiency is recorded in the presence of amino acids. The findings of this study could be useful in exploring the promoter-driven pore habitat of CO₂-rich hydrates in sediments to address climate change.

Sodium dodecyl sulfate (SDS) is a well-known surfactant, which can accelerate methane hydrate formation. In this work, methane hydrate formation kinetics were studied in the presence of SDS using a rocking cell apparatus in both temperature-ramping and isothermal modes. Ramping and isothermal experiments together suggest that SDS concentration plays a vital role in the formation kinetics of methane hydrate, both in terms of induction time and of final gas uptake. There is a trade-off between growth rate and gas uptake for the optimum SDS concentration, such that an increase in SDS concentration decreases the induction time but also decreases the gas storage capacity for a given volume. The experiments also confirm the potential use of the rocking cell for investigating hydrate promoters. It allows multiple systems to run in parallel at similar experimental temperature and pressure conditions, thus shortening the total experimentation time. Understanding methane hydrate formation and storage using SDS can facilitate large-scale applications such as natural gas storage and transportation.