Magnesium-Promoted Rapid Nucleation of Carbon Dioxide Hydrates

Abstract

Gas hydrates offer solutions in areas like CO 2 sequestration and desalination. However, their formation is severely limited by long induction (wait) times for nucleation, which range from hours to days. Many existing nucleation promotion techniques involve chemical additives, which invite environmental and process-related concerns. Here, we report a simple, passive, and environmentally friendly technique to significantly promote the nucleation of CO 2 hydrates: magnesium (in pure and alloy forms) triggers nucleation almost instantaneously. We report induction times of less than 1 min, which is the fastest induction time reported for any gas hydrate under stagnant conditions. This translates to Mg-promoted nucleation rates being 3000 times higher than the baseline. Statistically meaningful measurements of nucleation kinetics (in milliliter and liter-scale reactors), direct visualization of nucleation, and X-ray photoelectron spectroscopy (XPS)/Fourier-transform infrared spectroscopy (FTIR) analysis uncover several chemistry-related insights associated with Mg-based promotion. Importantly, the three-phase line of magnesium−water−CO 2 gas is key to promotion. Porous oxide layers, generation of H 2 nanobubbles, and chemisorption of CO 2 on Mg surfaces are other factors responsible for accelerated nucleation. Interestingly, Mg alloys exhibit faster nucleation promotion than pure Mg, which is significant in salt water medium. Overall, our work opens up pathways for faster synthesis of hydrates, which is critical to realizing applications.

Faster Nucleation of Ice at the Three-Phase Contact Line: Influence of Interfacial Chemistry

“…Silver iodide (AgI) is a strong promoter of ice nucleation; it has been observed that AgI particles nucleate ice at a much lower supercooling on direct contact with water drops (the presence of the air–water–AgI line) compared to the case of AgI particles immersed inside the water droplet. − Shaw et al reported that ice nuclei trigger faster nucleation of ice when placed on the water–air interface rather than being completely immersed. The benefits of three-phase nucleation have also been observed by the present group during nucleation of gas hydrates, − which are ice-like solids of gas and water and form at high pressures and temperatures close to 0 °C.…”

CO2 Hydrate Formation Kinetics and Morphology Observations Using High-Pressure Liquid CO2 Applicable to Sequestration

“…The role of stirring is 2-fold: it helps to constantly renew the aqueous water interface and to dissipate the heat released as a result of hydrate formation in the reactor. Mechanical stirring may also help to reduce nucleation time greatly, but it may require high energy input . The hydrate formation experiment is initiated after the start of stirring, and the process is carried out for the period of 12–24 h. A thin film was detected on the interface of liquid CO 2 and water in the experiments.…”

“…It is essential to accelerate the CO 2 hydrate formation kinetics to develop a more environmentally friendly, economical, and sustainable CO 2 sequestration technology. , Kinetic promoters have proven to improve hydrate formation kinetics for carbon dioxide capture and storage and gas storage applications. − Among kinetic promoters for hydrate formation, amino acids (protein building blocks) are more preferable to surfactants from a process operation point of view (foam formation) and environmental perspective . Veluswamy et al investigated the effect of three different amino acids, such as tryptophan, histidine, and arginine, on the kinetics of methane hydrate formation in stirred and unstirred tank reactors.…”

Sulfonated Castor Oil as an Efficient Biosurfactant for Improving Methane Storage in Clathrate Hydrates

“…However, the slow kinetics of gas hydrate formation is one of the most serious obstacles to implementing this technology. − Therefore, the hydrate community has focused on using special additives, namely, gas hydrate promoters (GHPs), that can accelerate the hydrate formation. , GHPs are divided into thermodynamic and kinetic types . Thermodynamic GHPs such as tetrahydrofuran, tetra- n -alkyl ammonium halides, and cyclopentane alter the equilibrium conditions of gas hydrate formation toward higher temperatures and lower pressures. − This means that they provide milder conditions for the hydrate formation, but the gas capacity of the hydrate decreases .…”

“…33−35 Therefore, the hydrate community has focused on using special additives, namely, gas hydrate promoters (GHPs), that can accelerate the hydrate formation. 23,36 GHPs are divided into thermodynamic and kinetic types. 37 Thermodynamic GHPs such as tetrahydrofuran, tetra-n-alkyl ammonium halides, and cyclopentane alter the equilibrium conditions of gas hydrate formation toward higher temperatures and lower pressures.…”