Methanol incorporation in clathrate hydrates and the implications for oil and gas pipeline flow assurance and icy planetary bodies

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DOIResolve DOI: http://doi.org/10.1073/pnas.1302812110
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TypeArticle
Journal titleProceedings of the National Academy of Sciences of the United States of America
ISSN0027-8424
Volume110
Issue21
Pages84378442; # of pages: 6
Subjectclathrate hydrate; methane; methanol; oil; tetrahydrofuran; unclassified drug; xenon; article; astronomy; chemical structure; gas pressure gauge; high temperature; hydrogen bond; low temperature; molecular dynamics; nuclear magnetic resonance; nuclear magnetic resonance spectroscopy; oil industry; priority journal; temperature dependence; vapor; X ray diffraction
AbstractOne of the best-known uses of methanol is as antifreeze. Methanol is used in large quantities in industrial applications to prevent methane clathrate hydrate blockages from forming in oil and gas pipelines. Methanol is also assigned a major role as antifreeze in giving icy planetary bodies (e.g., Titan) a liquid subsurface ocean and/or an atmosphere containing significant quantities of methane. In this work, we reveal a previously unverified role for methanol as a guest in clathrate hydrate cages. X-ray diffraction (XRD) and NMR experiments showed that at temperatures near 273 K, methanol is incorporated in the hydrate lattice along with other guest molecules. The amount of included methanol depends on the preparative method used. For instance, single-crystal XRD shows that at low temperatures, the methanol molecules are hydrogen-bonded in 4.4% of the small cages of tetrahydrofuran cubic structure II hydrate. At higher temperatures, NMR spectroscopy reveals a number of methanol species incorporated in hydrocarbon hydrate lattices. At temperatures characteristic of icy planetary bodies, vapor deposits of methanol, water, and methane or xenon show that the presence of methanol accelerates hydrate formation on annealing and that there is unusually complex phase behavior as revealed by powder XRD and NMR spectroscopy. The presence of cubic structure I hydrate was confirmed and a unique hydrate phase was postulated to account for the data. Molecular dynamics calculations confirmed the possibility of methanol incorporation into the hydrate lattice and show that methanol can favorably replace a number of methane guests.
Publication date
LanguageEnglish
AffiliationNational Research Council Canada (NRC-CNRC)
Peer reviewedYes
NPARC number21270644
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Record identifierc665dbc6-4c59-49eb-9a57-7547d4e108ee
Record created2014-02-17
Record modified2016-05-09
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