Mechanisms and Nucleation Rate of Methane Hydrate by Dynamical Nonequilibrium Molecular Dynamics
We investigate the effects of high solvated-methane concen- tration on methane-hydrate nucleation at 250 K and 500 atm. We consider solutions at four levels of methane molar fraction in the initial H2O−CH4 solution, χCH4 = 0.038, 0.044, 0.052, and 0.058, which are higher than (metastable) bulk super...
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ftunivferrarair:oai:iris.unife.it:11392/2406320 2024-02-11T10:05:49+01:00 Mechanisms and Nucleation Rate of Methane Hydrate by Dynamical Nonequilibrium Molecular Dynamics LAURICELLA, MARCO Ciccotti, Giovanni English, Niall J. Peters, Baron Meloni, Simone Lauricella, Marco Ciccotti, Giovanni English, Niall J. Peters, Baron Meloni, Simone 2017 ELETTRONICO http://hdl.handle.net/11392/2406320 https://doi.org/10.1021/acs.jpcc.7b05754 http://pubs.acs.org/journal/jpccck eng eng info:eu-repo/semantics/altIdentifier/wos/WOS:000414724300039 volume:121 issue:43 firstpage:24223 lastpage:24234 numberofpages:12 journal:JOURNAL OF PHYSICAL CHEMISTRY. C http://hdl.handle.net/11392/2406320 doi:10.1021/acs.jpcc.7b05754 info:eu-repo/semantics/altIdentifier/scopus/2-s2.0-85032819662 http://pubs.acs.org/journal/jpccck Electronic Optical and Magnetic Material Energy (all) Physical and Theoretical Chemistry Surface Coatings and Films info:eu-repo/semantics/article 2017 ftunivferrarair https://doi.org/10.1021/acs.jpcc.7b05754 2024-01-24T17:41:08Z We investigate the effects of high solvated-methane concen- tration on methane-hydrate nucleation at 250 K and 500 atm. We consider solutions at four levels of methane molar fraction in the initial H2O−CH4 solution, χCH4 = 0.038, 0.044, 0.052, and 0.058, which are higher than (metastable) bulk supersaturation. χCH4 is controlled independently of the temperature and pressure thanks to the use of special simulation techniques [Phys. Chem. Chem. Phys. 2011, 13, 13177]. These conditions mimic a possible increase of local methane concentration beyond supersaturation induced, for example, by freeze concentration or thermal fluctuations. The nucleation mechanism and kinetics are investigated using the dynamical approach to nonequilibrium molecular dynamics. We demonstrate a hydrate-forming/- ordering process of solvated methane and water molecules in a manner consistent with both the “blob” hypothesis and “cage adsorption hypothesis”: the system initially forms an amorphous nucleus at high methane concentration, which then gets ordered, forming the clathrate crystallite. We evaluate nucleation rates using both the methods of the mean first-passage time, i.e., the curve of the average time the system takes to reach a crystalline nucleus of given size, and survival probability, i.e., probability that up to a given time the system has not nucleated yet. We found a dependence of the nucleation rate on initial methane concentration of a form consistent with the dependence of classical nucleation theory rate on supersaturation and determined the relevant parameters of this relation. We found a very rapid increase of nucleation rate with solvated-methane concentration, proving that methane molar fraction, even beyond bulk supersaturation, is key at triggering the homogeneous nucleation of clathrate. We derive a kinetic equation that allows for estimation of the nucleation rate over a wide range of concentration conditions. Article in Journal/Newspaper Methane hydrate Università degli Studi di Ferrara: CINECA IRIS The Blob ENVELOPE(-124.933,-124.933,-73.400,-73.400) The Journal of Physical Chemistry C 121 43 24223 24234 |
institution |
Open Polar |
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Università degli Studi di Ferrara: CINECA IRIS |
op_collection_id |
ftunivferrarair |
language |
English |
topic |
Electronic Optical and Magnetic Material Energy (all) Physical and Theoretical Chemistry Surface Coatings and Films |
spellingShingle |
Electronic Optical and Magnetic Material Energy (all) Physical and Theoretical Chemistry Surface Coatings and Films LAURICELLA, MARCO Ciccotti, Giovanni English, Niall J. Peters, Baron Meloni, Simone Mechanisms and Nucleation Rate of Methane Hydrate by Dynamical Nonequilibrium Molecular Dynamics |
topic_facet |
Electronic Optical and Magnetic Material Energy (all) Physical and Theoretical Chemistry Surface Coatings and Films |
description |
We investigate the effects of high solvated-methane concen- tration on methane-hydrate nucleation at 250 K and 500 atm. We consider solutions at four levels of methane molar fraction in the initial H2O−CH4 solution, χCH4 = 0.038, 0.044, 0.052, and 0.058, which are higher than (metastable) bulk supersaturation. χCH4 is controlled independently of the temperature and pressure thanks to the use of special simulation techniques [Phys. Chem. Chem. Phys. 2011, 13, 13177]. These conditions mimic a possible increase of local methane concentration beyond supersaturation induced, for example, by freeze concentration or thermal fluctuations. The nucleation mechanism and kinetics are investigated using the dynamical approach to nonequilibrium molecular dynamics. We demonstrate a hydrate-forming/- ordering process of solvated methane and water molecules in a manner consistent with both the “blob” hypothesis and “cage adsorption hypothesis”: the system initially forms an amorphous nucleus at high methane concentration, which then gets ordered, forming the clathrate crystallite. We evaluate nucleation rates using both the methods of the mean first-passage time, i.e., the curve of the average time the system takes to reach a crystalline nucleus of given size, and survival probability, i.e., probability that up to a given time the system has not nucleated yet. We found a dependence of the nucleation rate on initial methane concentration of a form consistent with the dependence of classical nucleation theory rate on supersaturation and determined the relevant parameters of this relation. We found a very rapid increase of nucleation rate with solvated-methane concentration, proving that methane molar fraction, even beyond bulk supersaturation, is key at triggering the homogeneous nucleation of clathrate. We derive a kinetic equation that allows for estimation of the nucleation rate over a wide range of concentration conditions. |
author2 |
Lauricella, Marco Ciccotti, Giovanni English, Niall J. Peters, Baron Meloni, Simone |
format |
Article in Journal/Newspaper |
author |
LAURICELLA, MARCO Ciccotti, Giovanni English, Niall J. Peters, Baron Meloni, Simone |
author_facet |
LAURICELLA, MARCO Ciccotti, Giovanni English, Niall J. Peters, Baron Meloni, Simone |
author_sort |
LAURICELLA, MARCO |
title |
Mechanisms and Nucleation Rate of Methane Hydrate by Dynamical Nonequilibrium Molecular Dynamics |
title_short |
Mechanisms and Nucleation Rate of Methane Hydrate by Dynamical Nonequilibrium Molecular Dynamics |
title_full |
Mechanisms and Nucleation Rate of Methane Hydrate by Dynamical Nonequilibrium Molecular Dynamics |
title_fullStr |
Mechanisms and Nucleation Rate of Methane Hydrate by Dynamical Nonequilibrium Molecular Dynamics |
title_full_unstemmed |
Mechanisms and Nucleation Rate of Methane Hydrate by Dynamical Nonequilibrium Molecular Dynamics |
title_sort |
mechanisms and nucleation rate of methane hydrate by dynamical nonequilibrium molecular dynamics |
publishDate |
2017 |
url |
http://hdl.handle.net/11392/2406320 https://doi.org/10.1021/acs.jpcc.7b05754 http://pubs.acs.org/journal/jpccck |
long_lat |
ENVELOPE(-124.933,-124.933,-73.400,-73.400) |
geographic |
The Blob |
geographic_facet |
The Blob |
genre |
Methane hydrate |
genre_facet |
Methane hydrate |
op_relation |
info:eu-repo/semantics/altIdentifier/wos/WOS:000414724300039 volume:121 issue:43 firstpage:24223 lastpage:24234 numberofpages:12 journal:JOURNAL OF PHYSICAL CHEMISTRY. C http://hdl.handle.net/11392/2406320 doi:10.1021/acs.jpcc.7b05754 info:eu-repo/semantics/altIdentifier/scopus/2-s2.0-85032819662 http://pubs.acs.org/journal/jpccck |
op_doi |
https://doi.org/10.1021/acs.jpcc.7b05754 |
container_title |
The Journal of Physical Chemistry C |
container_volume |
121 |
container_issue |
43 |
container_start_page |
24223 |
op_container_end_page |
24234 |
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1790603005437935616 |