Aluminum-Based Promotion of Nucleation of Carbon Dioxide Hydrates

Abstract

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.

Magnesium-Promoted Rapid Nucleation of Carbon Dioxide Hydrates

“…Presently, we report that magnesium (Mg) can induce nucleation of CO 2 hydrates within a few minutes; this represents a 500 times increase in nucleation rate, compared to our previous results on aluminum-based promotion. 70 Our best current results show nucleation occurring in less than 1 min, which is very close to the instantaneous, on-demand nucleation that is required for practical applications. Carefully conducted experiments and direct visualization of nucleation enable statistically meaningful measurements of nucleation, which are often lacking in literature.…”

“…Mg-based promotion is therefore ∼500 times faster than Al-based promotion. 70 We can also compare the present results with the comprehensive assessment of nucleation rates of CO 2 hydrates obtained by Maeda. 83 Mg-promoted nucleation rates from our present experiments (large water volume) are ∼70 times larger than Maeda's measurements using a HP-ALTA apparatus; this again highlights the benefits of Mg. Interestingly, our baseline nucleation rates (without the presence of Mg) are lower than those reported by Maeda.…”

“…There have been a limited number of studies on surface-promoted nucleation of hydrates (a passive technique for nucleation promotion). Metals and metal oxide suspensions have been experimentally shown to assist in nucleation promotion and have also been studied in conjunction with surfactants. − Passive promotion and the underlying mechanisms have also been studied via molecular dynamics simulations. − A recent discovery by the present group involved the use of aluminum surfaces to promote the nucleation of CO 2 hydrates . Statistically significant measurements showed CO 2 hydrates nucleating in ∼3 h on aluminum surfaces (with no nucleation observed in the absence of aluminum).…”

“…65−69 A recent discovery by the present group involved the use of aluminum surfaces to promote the nucleation of CO 2 hydrates. 70 Statistically significant measurements showed CO 2 hydrates nucleating in ∼3 h on aluminum surfaces (with no nucleation observed in the absence of aluminum). It was hypothesized that hydrogen bubbles generated at the aluminum−water interface were responsible for such promotion.…”

Capturing Carbon Dioxide on the Wet SBA-15 Mesoporous Molecular Sieves with Different Surfactants

“…Therefore, from a financial perspective, it is necessary to study methods that can form hydrates under moderate operating conditions. In the existing literature, there are many studies on the formation of hydrate phases by using accelerators under appropriate circumstances, some of which also help to accelerate the hydrate formation process. − …”