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

Authors:
; ;
Publication Date:
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1396726
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Fuel
Additional Journal Information:
Journal Volume: 197; Journal Issue: C; Related Information: CHORUS Timestamp: 2017-10-04 15:07:09; Journal ID: ISSN 0016-2361
Publisher:
Elsevier
Country of Publication:
United Kingdom
Language:
English

Citation Formats

Nguyen, Ngoc N., Nguyen, Anh V., and Dang, Liem X. The inhibition of methane hydrate formation by water alignment underneath surface adsorption of surfactants. United Kingdom: N. p., 2017. Web. doi:10.1016/j.fuel.2017.02.061.
Nguyen, Ngoc N., Nguyen, Anh V., & Dang, Liem X. The inhibition of methane hydrate formation by water alignment underneath surface adsorption of surfactants. United Kingdom. doi:10.1016/j.fuel.2017.02.061.
Nguyen, Ngoc N., Nguyen, Anh V., and Dang, Liem X. Thu . "The inhibition of methane hydrate formation by water alignment underneath surface adsorption of surfactants". United Kingdom. doi:10.1016/j.fuel.2017.02.061.
@article{osti_1396726,
title = {The inhibition of methane hydrate formation by water alignment underneath surface adsorption of surfactants},
author = {Nguyen, Ngoc N. and Nguyen, Anh V. and Dang, Liem X.},
abstractNote = {},
doi = {10.1016/j.fuel.2017.02.061},
journal = {Fuel},
number = C,
volume = 197,
place = {United Kingdom},
year = {Thu Jun 01 00:00:00 EDT 2017},
month = {Thu Jun 01 00:00:00 EDT 2017}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1016/j.fuel.2017.02.061

Citation Metrics:
Cited by: 1work
Citation information provided by
Web of Science

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  • 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)more » 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. This work was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences. The calculations were carried out using computer resources provided by the Office of Basic Energy Sciences.« less
  • The University of Alberta obtained equilibrium three-phase water liquid-hydrocarbon liquid-solid hydrate data for the methane--isobutane--water system and for six multicomponent mixtures containing isobutane, at pressures up to 2200 psia and temperatures above 32/sup 0/F. The theory of J.H. van der Waals and J.C. Platteeuw for predicting hydrate forming conditions in gases was modified to make it applicable to gas and liquid mixtures. The method was also applied to the prediction of the four-phase equilibrium locus.
  • Gas hydrates formed under moderated conditions open up novel approaches to tackling issues related to energy supply, gas separation, and CO 2 sequestration. Several additives like tetra-n-butylammonium bromide (TBAB) have been empirically developed and used to promote gas hydrate formation. Here we report unexpected experimental results which show that TBAB inhibits CO 2 gas hydrate formation when used at minuscule concentration. We also used spectroscopic techniques and molecular dynamics simulation to gain further insights and explain the experimental results. They have revealed the critical role of water alignment at the gas-water interface induced by surface adsorption of tetra-n-butylammonium cation (TBAmore » +) which gives rise to the unexpected inhibition of dilute TBAB solution. The water perturbation by TBA + in the bulk is attributed to the promotion effect of high TBAB concentration on gas hydrate formation. We explain our finding using the concept of activation energy of gas hydrate formation. Our results provide a step toward to mastering the control of gas hydrate formation.« less
  • Optical second harmonic generation is employed to investigate the adsorption of soluble naphthalene sulfonates from the bulk solution to the air/water interface in the presence of excess counter ions. Both the surface density of surfactant molecules and the surface pressure were measured as functions of surfactant concentration in solution to yield the adsorption isotherm and the surface pressure/area isotherm. The system investigated shows nonideal gas behavior. The ratio of the activity coefficients at the surface and in the bulk is not unity; however both appear to be constant over the concentration range probed.