The inhibition of methane hydrate formation by water alignment underneath surface adsorption of surfactants

Nguyen, Ngoc N., Nguyen, Anh V. and Dang, Liem X. (2017) The inhibition of methane hydrate formation by water alignment underneath surface adsorption of surfactants. Fuel, 197 488-496. doi:10.1016/j.fuel.2017.02.061


Author Nguyen, Ngoc N.
Nguyen, Anh V.
Dang, Liem X.
Title The inhibition of methane hydrate formation by water alignment underneath surface adsorption of surfactants
Journal name Fuel   Check publisher's open access policy
ISSN 0016-2361
1873-7153
Publication date 2017-06-01
Sub-type Article (original research)
DOI 10.1016/j.fuel.2017.02.061
Open Access Status Not yet assessed
Volume 197
Start page 488
End page 496
Total pages 9
Place of publication Oxford, United Kingdom
Publisher Elsevier
Collection year 2018
Language eng
Formatted abstract
Sodium dodecyl sulfate (SDS) has been widely shown to strongly promote the formation of methane hydrate. Here we show that SDS displays an extraordinary inhibition effect on methane hydrate formation when the surfactant is used in sub-millimolar concentration (around 0.3 mM). We have also employed Sum Frequency Generation vibrational spectroscopy (SFG) and molecular dynamics simulation (MDS) to elucidate the molecular mechanism of this inhibition. The SFG and MDS results revealed a strong alignment of water molecules underneath surface adsorption of SDS in its sub-millimolar solution. Interestingly, both the alignment of water and the inhibition effect (in 0.3 mM SDS solution) went vanishing when an oppositely-charged surfactant (tetra-n-butylammonium bromide, TBAB) was suitably added to produce a mixed solution of 0.3 mM SDS and 3.6 mM TBAB. Combining structural and kinetic results, we pointed out that the alignment of water underneath surface adsorption of dodecyl sulfate (DS) anions gave rise to the unexpected inhibition of methane hydration formation in sub-millimolar solution of SDS. The adoption of TBAB mitigated the SDS-induced electrostatic field at the solution's surface and, therefore, weakened the alignment of interfacial water which, in turn, erased the inhibition effect. We discussed this finding using the concept of activation energy of the interfacial formation of gas hydrate. The main finding of this work is to reveal the interplay of interfacial water in governing gas hydrate formation which sheds light on a universal molecular-scale understanding of the influence of surfactants on gas hydrate formation.
Keyword Gas hydrate
Methane
Surfactant
Water structure
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Chemical Engineering Publications
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