Hydrate-based CO 2 storage/sequestration (HBCS) technique could potentially fulfill the mandate of the Sustainable Development Goal (SDG) 13 toward efficient and safe storage of CO 2 through successful lab-scale experimentation in overcoming the existing storage capacity challenges. In this article, we carefully reviewed and discussed the reported fundamental lab-scale experimental attempts to successfully store CO 2 as hydrate in sediments. The CO 2 hydrate formation thermodynamics, kinetics, and mechanism insights in porous media are critically discussed to reveal the state of the art and the current challenges facing the implementation of the HBCS technique and provide guidelines and pathways toward a high CO 2 storage capacity. In addition, factors affecting CO 2 hydrate formation and hydrate formation mechanisms in various types of porous media are discussed. Factors that mainly control the CO 2 storage capacity in porous media are driving force, porosity, capillary effect, gas and liquid permeability, particle size, and surface area. However, mass transfer limitation, potential storage site, CO 2 transportation, CO 2 injection technique, cost, environmental constraints, and CO 2 stability are the main challenges toward the technological readiness of the HBCS. The findings in this work provide useful guidelines and pathways which could lead to an increase in CO 2 storage capacity as hydrate for cleaner earth in the future.

Ionis liquids (ILs) are promising novel thermodynamic gas hydrate inhibitors (THIs) that have gained an ongoing experimental and modeling research prospect over a decade. In view of this, the path to developing desirable ionic liquids THIs depends on understanding the state-of-the-art methods of ILs hydrate inhibition impacts and factors that influence their performance. This review provides a holistic summary of the use of ILs as THIs. Almost all the available thermodynamic hydrate inhibition data of different gas systems in the presence of ILs at varying concentrations were critically reviewed and analyzed. Also, all ILs hydrate-related phase behavior modeling studies and their prediction accuracies are discussed in this work. The hydrate phase boundary inhibition effects of each IL are provided alongside factors that affect their inhibition performance. The study showed that IL cations, anions, and chain length characteristics control their hydrate inhibition impacts. By far, a narrow hydrate suppression temperature window below 3 K at 10 wt % IL concentration has been achieved with accurate predictions using various models. This narrow THI performance window could be enhanced by exploring novel IL families with low molecular weights, well-optimized cation–anion interactions, and active hydrogen bonding interactive functionalities. The findings presented in this work are relevant for future IL-related breakthrough research in hydrate inhibition technologies.

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CO 2 sequestration as hydrates has captured enormous research interest in recent years due to its high storage capacity. However, the slow hydrate formation kinetics poses a strong challenge in its applicability and urges the need for additives (kinetic promoters) to accelerate the hydrate formation kinetics. This study investigates the performance of amino acid solutions in brine (3.3 wt % NaCl) on CO 2 hydrate formation and dissociation kinetics. The kinetics of hydrate formation and dissociation was evaluated at varying concentrations (0.2, 0.5, 0.8, and 1 wt %) of L-methionine, L-isoleucine, and L-threonine solutions in brine using a high-pressure hydrate reactor at 4 MPa, and formation temperature of 274.15 K, and a dissociation temperature of 277.15 K. CO 2 hydrate formation and dissociation experiments were also conducted using sodium dodecyl sulfate (SDS), pure water, and brine systems as standards for comparison. The findings show that all the studied amino acid systems show hydrate inhibition as compared to the pure water system with 35−41% reduction in CO 2 storage capacity. Further, L-methionine exhibited an optimum performance with a slight promotional effect at 0.2 wt % with the lowest induction time (35.6 min) and the highest CO 2 uptake (42.08 mol/ mmol) among the studied amino acid systems. However, comparing L-methionine with SDS shows less induction time for SDS (28.48 min), indicating kinetic promotion of SDS over L-methionine in the presence of brine. The dissociation kinetics findings reveal the lowest dissociation rate for L-methionine and a prolonged time of CO 2 release compared to L-threonine and L-isoleucine, respectively. Nevertheless, all the considered amino acid systems exhibit more inhibition or stability for hydrate dissociation as compared to the pure water system. However, compared to SDS and brine systems, the amino acids L-methionine and L-isoleucine show a slight promotion effect, unlike L-threonine which exhibits strong kinetic inhibition. The results thus suggest that amino acid solutions in brine stabilize hydrate dissociation; however, the CO 2 hydrate formation inhibition in brine is quite discouraging for CO 2 storage purposes. Instead, applying amino acids in flow assurance could be an additional advantage due to the presence of brine in practical reservoir fluids during production.

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