Gas
hydrate formation has several applications in CO2 sequestration,
flow assurance, and desalination. Nucleation of hydrates
is constrained by very high induction (wait) times, which necessitates
the use of complex nucleation promotion techniques to form hydrates.
Presently, we report the discovery of a simple, passive nucleation
promotion technique, wherein an aluminum surface significantly
accelerates nucleation of CO2hydrates. Statistically
meaningful measurements of induction times for CO2 hydrate
nucleation were undertaken using water droplets as individual microsystems
for hydrate formation. The influence of various metal surfaces, droplet
size, CO2 dissolution time, and the presence of salts in
water on nucleation kinetics was characterized. Interestingly, we
observe nucleation initiation only on aluminum surfaces, the influence
of which cannot be replicated by salts of aluminum. We discover that
the aluminum–water interface is responsible for nucleation
promotion. We hypothesize that hydrogen bubbles generated at the aluminum–water
interface are responsible for nucleation promotion.
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.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.