Molecular dynamics simulations of the formation of ethane clathrate hydrates

Wilson, Daniel T.; Barnes, Brian C.; Wu, David T.; Sum, Amadeu K.

doi:10.1016/j.fluid.2015.12.001

Cited by 22 publications

(27 citation statements)

References 15 publications

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“…He et al investigated the nucleation of CO 2 hydrates by microsecond molecular dynamics simulations and observed the amorphousness of incipient hydrates and the increase in stability of hydrate with formation time. Wilson et al analyzed the minor differences in size metrics of occupied and empty hydrate cages and elucidated the transformation of hydrate cases from kinetically preference to thermodynamically stability. Limited by the temporal–spatial scale and molecule numbers, the molecular dynamics simulations cannot reveal the whole hydrate formation process that may last tens of minutes.…”

Section: Resultsmentioning

confidence: 99%

Quantitative analysis of CO₂ hydrate formation in porous media by proton NMR

Zheng

Yang

et al. 2019

AIChE Journal

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Gas hydrate is a nonstoichiometric crystal compound formed from water and gas. Most nonvisual studies on gas hydrate are unable to detect how much water is converted to hydrates, and thus, the hydrate stoichiometry calculations are inaccurate. This study investigated the CO 2 hydrate formation process in porous media directly and quantitatively. The characteristics of the time-variable consumption of hydrate formation indicated a two-stage formation, hydrate enclathration and continuous occupancy. The enclathration stage occurred in the first 20 min of the formation when considerable heat is released. The continuous occupancy stage lasted longer than the hydrate enclathration because the empty cages in previously formed hydrates would also be occupied. The higher formation pressures can accelerate water consumption and increase cage occupancy. The compositions of completely formed CO 2 hydrates at 2.7, 3.0, and 3.3 MPa and 275.15 K were determined as CO 2 Á6.90H 2 O, CO 2 Á6.70H 2 O, and CO 2 Á6.49H 2 O, respectively.

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Section: Resultsmentioning

confidence: 99%

Quantitative analysis of CO₂ hydrate formation in porous media by proton NMR

Zheng

Yang

et al. 2019

AIChE Journal

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“…When simulating in the initial state, the (super)saturated solution is in equilibrium with a spherical bubble of CO 2 gas. A similar bubble gas reservoir setup has been used previously to study methane, 27 ethane, 34 and propane 35 clathrate formation. This spherical bubble reservoir is a consequence of the necessarily small size of the system to make the simulations tractable.…”

Section: Methodsmentioning

confidence: 99%

“…The 4 1 5 10 6 2 cage has also been of importance in the formation of ethane clathrate. 25 Metastable intermediates are normally transient and easily transformed in simulations to kinetically and thermodynamically favored stable products but not in clathrates, as this requires substantial hydrogen bond breaking and remaking.…”

Section: Introductionmentioning

confidence: 99%

Molecular Understanding of Homogeneous Nucleation of CO₂ Hydrates Using Transition Path Sampling

Arjun

Bolhuis

2020

J. Phys. Chem. B

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Carbon dioxide hydrate is a solid built from hydrogen-bond stabilized water cages that encapsulate individual CO 2 molecules. As potential candidates for reducing greenhouse gases, hydrates have attracted attention from both the industry and scientific community. Under high pressure and low temperature, hydrates are formed spontaneously from a mixture of CO 2 and water via nucleation and growth. Yet, for moderate undercooling, i.e., moderate supersaturation, studying hydrate formation with molecular simulations is very challenging due to the high nucleation barriers involved. We investigate the homogeneous nucleation mechanism of CO 2 hydrate as a function of temperature using transition path sampling (TPS), which generates ensembles of unbiased dynamical trajectories across the high barrier between the liquid and solid states. The resulting path ensembles reveal that at high driving force (low temperature), amorphous structures are predominantly formed, with 4 1 5 10 6 2 cages being the most abundant. With increasing temperature, the nucleation mechanism changes, and 5 12 6 2 becomes the most abundant cage type, giving rise to the crystalline sI structure. Reaction coordinate analysis can reveal the most important collective variable involved in the mechanism. With increasing temperature, we observe a shift from a single feature (size of the nucleus) to a 2-dimensional (size and cage type) variable as the salient ingredient of the reaction coordinate, and then back to only the nucleus size. This finding is in line with the underlying shift from an amorphous to a crystalline nucleation channel. Modeling such complex phase transformations using transition path sampling gives unbiased insight into the molecular mechanisms toward different polymorphs, and how these are determined by thermodynamics and kinetics. This study will be beneficial for researchers aiming to produce such hydrates with different polymorphic forms.

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“…Simulations have also been performed with a flat liquid layer in contact with gaseous methane [26,27], or other gas species [28,29] but more recently, simulations of hydrate formation in the vicinity of curved water-gas surfaces have also been performed [30]. The simulations are carried out under the operation of a molecular dynamics thermostat which dissipates the heat released from the hydrate formation process in a non-directional manner, not necessarily consistent with heat transfer in the physical system (but in a manner which restores proper thermal equilibrium to the system).…”

Section: Nucleationmentioning

confidence: 99%

Some current challenges in clathrate hydrate science: Nucleation, decomposition and the memory effect

Ripmeester

Alavi

2016

Current Opinion in Solid State and Materials Science

124

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Molecular dynamics simulations of the formation of ethane clathrate hydrates

Cited by 22 publications

References 15 publications

Quantitative analysis of CO₂ hydrate formation in porous media by proton NMR

Quantitative analysis of CO₂ hydrate formation in porous media by proton NMR

Molecular Understanding of Homogeneous Nucleation of CO₂ Hydrates Using Transition Path Sampling

Some current challenges in clathrate hydrate science: Nucleation, decomposition and the memory effect

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Molecular dynamics simulations of the formation of ethane clathrate hydrates

Cited by 22 publications

References 15 publications

Quantitative analysis of CO2 hydrate formation in porous media by proton NMR

Quantitative analysis of CO2 hydrate formation in porous media by proton NMR

Molecular Understanding of Homogeneous Nucleation of CO2 Hydrates Using Transition Path Sampling

Some current challenges in clathrate hydrate science: Nucleation, decomposition and the memory effect

Contact Info

Product

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Quantitative analysis of CO₂ hydrate formation in porous media by proton NMR

Quantitative analysis of CO₂ hydrate formation in porous media by proton NMR

Molecular Understanding of Homogeneous Nucleation of CO₂ Hydrates Using Transition Path Sampling