Formation and phase equilibria of gas hydrates confined in hydrophobic nanoparticles
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Published version
Author(s)
Ai, Lu
Maitland, Geoffrey C
Hellgardt, Klaus
Type
Journal Article
Abstract
The promotion of gas hydrate formation is of fundamental importance to facilitate its great potential applications in, for example, gas separation, transportation and energy storage. The employment of Dry Water (DW), which is a powdery Pickering system composed of macro water droplets surrounded by stabilising hydrophobic nanoparticles, is considered an effective method for enhancing hydrate formation. The promotion mechanism underlying this observation, however, has yet to be well understood. In this work, the effect of DW on both formation kinetics and thermodynamic stability of gas hydrates was investigated using a micro differential scanning calorimetry (µDSC) in CH4 and CO2 hydrate systems, using two different hydrophobic nanoparticles. Distinctly shorter induction times and higher conversion ratios were observed for DW compared to bulk water. The DW system stabilised by more hydrophobic nanoparticles showed benefits in accelerating nucleation, while the other system, which consisted of smaller DW droplets, led to a superior enhancement of hydrate growth. Besides the effect on formation kinetics, it was also noted that DW influenced the µDSC hydrate dissociation peak characteristics, including melting points and melting peak shapes. This phenomenon suggested that the centre- and surface-droplet hydrates in DW may have different structures, due to the “hydrophobic effect” of the nanoparticles structuring the near-surface water, so exhibiting melting points corresponding to bulk hydrate or to a more structured surface hydrate (with raised melting point), respectively. To support this “hydrophobic effect” hypothesis, a series of hydrate and ice formation experiments were conducted in porous media having different hydrophobicity, the results of which demonstrated that hydrates adjoining confined hydrophobized surfaces, in other systems similar to DW, also displayed higher melting temperatures.
Date Issued
2024-10-05
Date Acceptance
2024-06-16
Citation
Chemical Engineering Science, 2024, 298
ISSN
0009-2509
Publisher
Elsevier BV
Journal / Book Title
Chemical Engineering Science
Volume
298
Copyright Statement
© 2024 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC license (http://creativecommons.org/licenses/by-nc/4.0/.
Identifier
http://dx.doi.org/10.1016/j.ces.2024.120392
Publication Status
Published
Article Number
120392
Date Publish Online
2024-06-17