Hydrate nucleation and growth on water droplets acoustically-levitated in high-pressure natural gas

Jeong, Kwanghee; Metaxas, Peter J.; Chan, Joel; Kuteyi, Temiloluwa O.; Aman, Zachary M.; Stanwix, Paul L.; Johns, Michael L.; May, Eric F.

doi:10.1039/c9cp04403e

Cited by 26 publications

(21 citation statements)

References 34 publications

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“…Alternatively, mechanical stirring can significantly decrease the nucleation time; however, it increases the complexity of the high-pressure reactor in terms of plugging and requires energy input. ,, Thermodynamic promoters, which alter the hydrate equilibrium curve, can also influence the induction time for hydrate nucleation. − Thermodynamic promoters are often combined with kinetic promoters to enhance hydrate formation. − However, these promoters again involve the use of chemicals such as tetra- n -butylammonium bromide (TBAB) or tetrahydrofuran (THF), which are often required in large quantities and not considered environmentally friendly. Other methods, such as utilizing hydrate seeds, supersaturation, ice melts, amino acids, electronucleation, and acoustics have also been studied to facilitate the nucleation of hydrates. − Electronucleation has been studied by the authors of this study: even though it can enable fast nucleation, it introduces additional complexities in the reactor …”

Section: Introductionmentioning

confidence: 99%

Magnesium-Promoted Rapid Nucleation of Carbon Dioxide Hydrates

Kar

Acharya

Bhati

et al. 2021

ACS Sustainable Chem. Eng.

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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.

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Section: Introductionmentioning

confidence: 99%

Magnesium-Promoted Rapid Nucleation of Carbon Dioxide Hydrates

Kar

Acharya

Bhati

et al. 2021

ACS Sustainable Chem. Eng.

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“…Each droplet acts as an independent system, making it possible to obtain statistically significant data, bearing in mind that nucleation is stochastic and that hydrate formation experiments are usually very long. The use of droplets/bubbles to study nucleation and formation of hydrates − and ice , is widely employed. This approach also enables high-quality visualization of kinetics and crystal growth.…”

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confidence: 99%

Aluminum-Based Promotion of Nucleation of Carbon Dioxide Hydrates

Acharya

Kar

Shahriari

et al. 2020

J. Phys. Chem. Lett.

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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.

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“…The methods to eliminate container-driven effects on nucleation have recently been expanded to include acoustic levitation. For examining hydrate nucleation, previous investigations have been limited to single droplets contained within a cooling chamber. , Expanding on these foundational studies, aqueous solutions containing 19.2 wt % THF were frozen to form THF hydrate while levitated in different configurations of three positions. Digital and thermal images were captured simultaneously of the single-, double-, or triple-droplet systems.…”

Section: Discussionmentioning

confidence: 99%

“…For example, hydrates have been formed on stationary hydrophobic surfaces or suspended from the tips of fine glass filaments. , Equally, hydrate growth was investigated in hydrophobic, hydrocarbon-oil-based suspensions . Most notably, Jeong et al formed natural gas hydrates with water droplets suspended in an acoustic levitator (i.e., levitated hydrates), where no solid interface was in contact with the liquid sample . Their investigations determined that levitated hydrates had more nucleation sites than those grown from solid surfaces, although the nucleation work was greater .…”

Section: Introductionmentioning

confidence: 99%

Interfacial Effects during Phase Change in Multiple Levitated Tetrahydrofuran Hydrate Droplets

et al. 2023

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Recent strategies developed to examine the nucleation of crystal structures like tetrahydrofuran (THF) hydrates without the effects of a solid interface have included acoustic levitation, where only a liquid−gas interface initially exists. However, the ability now exists to levitate and freeze multiple droplets simultaneously, which could reveal interdroplet effects and provide further insight into interfacial nucleation phenomena. In this study, using direct digital and infrared imaging techniques, the freezing of up to three simultaneous THF hydrate droplets was investigated for the first time. Nucleation was initiated at the aqueous solution−air interface. Two pseudo-heterogeneous mechanisms created additional nucleation interfaces: one from cavitation effects entraining microbubbles and another from subvisible ice particles, also called hydrate-nucleating particles (HNPs), impacting the droplet surface. For systems containing droplets in both the second and third positions, nucleation was statistically simultaneous between all droplets. This effect may have been caused by the high liquid−solid interfacial pressures that developed at nucleation, causing some cracking in the initial hydrate shell around the droplet and releasing additional HNPs (now of hydrate) into the air. During crystallization, the THF hydrate droplets developed a completely white opacity, termed optical clarity loss (OCL). It was suggested that high hydrate growth rates within the droplet resulted in the capture of tiny air bubbles within the solid phase. In turn, light refraction through many smaller bubbles resulted in the OCL. These bubbles created structural inhomogeneities, which may explain how the volumetric expansion of the droplets upon complete solidification was 23.6% compared with 7.4% in pure, stationary THF hydrate systems. Finally, the thermal gradient that developed between the top and bottom of the droplet during melting resulted in a surface tension gradient along the air−liquid interface. In turn, convective cells developed within the droplet, causing it to spin rapidly about the horizontal axis.

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Hydrate nucleation and growth on water droplets acoustically-levitated in high-pressure natural gas

Abstract: We present the first quantitative measurements of hydrate formation probability, nucleation rate and growth on a water droplet suspended within a high pressure natural gas by acoustic levitation.

Cited by 26 publications

References 34 publications

Magnesium-Promoted Rapid Nucleation of Carbon Dioxide Hydrates

Magnesium-Promoted Rapid Nucleation of Carbon Dioxide Hydrates

Aluminum-Based Promotion of Nucleation of Carbon Dioxide Hydrates

Interfacial Effects during Phase Change in Multiple Levitated Tetrahydrofuran Hydrate Droplets

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