Perspectives on Molecular Mechanisms of Hydrate Formation and Growth at Interfaces: A Mini-Review

Abstract

Hydrate-based engineering applications hold significant promise due to their physical feasibility and low energy consumption. However, key challengesincluding operating conditions, formation and growth rates, and gas storage capacitycontinue to impact their viability as sustainable technologies. This mini-review offers key insights into molecular mechanisms governing hydrate nucleation and growth at guest-water interfaces, specifically examining the role of mass transfer thermodynamics across the interface in either promoting or inhibiting gas hydrate formation. Additionally, this review highlights recent advancements, emerging research opportunities, and potential commercialization pathways for these technologies. With continued development, technologies utilizing hydrates have the capability to play a transformative role across multiple industries, offering a more sustainable alternative to existing commercial solutions.

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Gas-hydrate-based engineering applications.

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Top: Molecular-level depiction of a representative interface under study, along with a schematic illustration of the X-ray scattering setup. Bottom: Electron density profile and conceptual illustration of the guest-concentrated interfacial layer. Reproduced from Nase et al. Copyright 2012 American Chemical Society.

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Top: Simulation snapshots for the systems with flat (left) and cylindrical (right) interfaces. Orange spheres symbolize methane and cyan spheres represent water oxygen atoms. Bottom: Methane solubility in water (left) and methane hydrate nucleation rates (right) estimated at the thermodynamic conditions and at the different interfacial curvatures investigated in Walsh et al.’s study. Reproduced from Walsh et al. Copyright 2011 American Chemical Society.

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Top: Willard–Chandler instantaneous interface with the trough (cyan) and crest (blue) regions. Bottom: Schematic representation of the gas molecule diffusion across the instantaneous interface. Reproduced from Ansari et al. Copyright 2020 American Chemical Society.

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Mechanism of action of surface-active chemicals in promoting gas hydration formation.

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(a) Simulation snapshots for the configurations for the systems without (left) and with (right) DSOS molecules at the Willard-Chandler instantaneous interfaces (represented in bright yellow). (b) Deformation free energy ΔG _def (pink bars) responsible for the formation of instantaneous interface undulations, together with the associated methane solubility (blue circles), presented for systems without and with DSOS at different concentrations. (c) Methane hydrate growth rate at 9 MPa and 275 K (yellow bars), together with the associated methane solubility (blue circles), for systems without and with DSOS at varying concentrations. Reproduced or adapted with permission from ref . Copyright 2025 the Royal Society of Chemistry.

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(A) Simulation snapshots for the configuration for the system at anti-agglomerant surface density of 0.67 molecule/nm². The free methane molecule, analyzed for free energy pathways, is represented as a red sphere. (B) Top: Schematic representation of the minimal (a), intermediate (b), and maximal (c) scenarios. Gray lines depict n-dodecane, while blue line indicate anti-agglomerant molecules. Bottom: Free energy pathways obtained with the well-tempered metadynamics simulation techniques. (C) Free energy pathways for the single methane molecule moving across the interface when the anti-agglomerant molecules are either free (black) or frozen in position (red). Reproduced from Sicard et al. Copyright 2018 American Chemical Society.

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Left: Potential of mean force profiles for a single methane molecule migrating from the hydrocarbon phase to the aqueous phase. The results were shown for simulated systems without (blue) and with SACs at low (green) and high (red) surface densities. Right: Fitting data for the deformation free energy (ΔG _def), the adsorption barrier (ΔG _barrier), the effective binding free energy (ΔG _bind) to a multiple linear regression model associated with corresponding methane solubility (circles) achieved for systems without and with SACs (SDS and CAP) at varying surface densities at the interface. Reproduced from Phan et al. Available under a CC-BY 4.0 license. Copyright 2023 Elsevier B.V.

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Variations in surface thermodynamics across a guest–water interface. Reproduced from Broderick et al. Copyright 2019 American Chemical Society.