The effect of surfactants on hydrate particle agglomeration in liquid hydrocarbon continuous systems: a molecular dynamics simulation study

Fang, Bin; Ning, Fulong; Hu, Shikai; Guo, Dongdong; Ou, Wenjia; Wang, Cunfang; Wen, Jiang; Sun, Jiaxin; Liu, Zhichao; Koh, Carolyn A.

doi:10.1039/d0ra04088f

Cited by 22 publications

(19 citation statements)

References 66 publications

(96 reference statements)

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“…The compact barrier has more opportunities to be formed with longer-tail AA molecules in longer-chain liquid hydrocarbons. The observations in this study are in agreement with MD simulation results in prior work …”

Section: Resultssupporting

confidence: 93%

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Structural Effects of Gas Hydrate Antiagglomerant Molecules on Interfacial Interparticle Force Interactions

Monteiro

et al. 2021

Langmuir

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Gas hydrate interparticle cohesive forces are important to determine the hydrate crystal particle agglomeration behavior and subsequent hydrate slurry transport that is critical to preventing potentially catastrophic consequences of subsea oil/gas pipeline blockages. A unique high-pressure micromechanical force apparatus has been employed to investigate the effect of the molecular structure of industrially relevant hydrate antiagglomerant (AA) inhibitors on gas hydrate crystal interparticle interactions. Four AA molecules with known detailed structures [quaternary ammonium salts with two long tails (R1) and one short tail (R2)] in which the R1 has 12 carbon (C12) and 8 carbon (C8) and saturated (C–C) versus unsaturated (CC) bonding are used in this work to investigate their interfacial activity to suppress hydrate crystal interparticle interactions in the presence of two liquid hydrocarbons (n-dodecane and n-heptane). All AAs were able to reduce the interparticle cohesive force from the baseline (23.5 ± 2.5 mN m–1), but AA-C12 shows superior performance in both liquid hydrocarbons compared to the other AAs. The interfacial measurements indicate that the AA with an R1 longer alkyl chain length can provide a denser barrier, and the AA molecules may have higher packing density when the AA R1 alkyl tail length is comparable to that of the liquid hydrocarbon chain on the gas hydrate crystal surface. Increasing the salinity can promote the effectiveness of an AA molecule and can also eliminate the effect of longer particle contact times, which typically increases the interparticle cohesive force. This work reports the first experimental investigation of high-performance known molecular structure AAs under industrially relevant conditions, showing that these molecules can reduce the interfacial tension and increase the gas hydrate–water contact angle, thereby minimizing the gas hydrate interparticle interactions. The structure–performance relation reported in this work can be used to help in the design of improved AA inhibitor molecules that will be critical to industrial hydrate crystal slurry transport.

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Section: Resultssupporting

confidence: 93%

“…The observations in this study are in agreement with MD simulation results in prior work. 70 Effect of NaCl. It is known that salt can inhibit hydrate formation and shift the hydrate equilibrium conditions, 1,71−75 thereby affecting the performance of AAs.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Structural Effects of Gas Hydrate Antiagglomerant Molecules on Interfacial Interparticle Force Interactions

Monteiro

et al. 2021

Langmuir

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“…The cutoff radius is set at 1.05 nm. 27 The standard Lorentz−Berthelot mixing rules are employed to calculate the cross interactions between different species. First, NVT ensemble simulation is conducted for 1 ns at 270 K to relax the initial configuration (the hydrate layer is kept frozen) due to the instability of the hydrate.…”

Section: Calculation Model and Methodsmentioning

confidence: 99%

“…The particle mesh Ewald (PME) method is used to calculate the electrostatic interaction between particles. The cutoff radius is set at 1.05 nm . The standard Lorentz–Berthelot mixing rules are employed to calculate the cross interactions between different species.…”

Section: Calculation Model and Methodsmentioning

confidence: 99%

“…Maddah et al 26 found that AFP-III has a good inhibitory effect on hydrate growth and the length of the side chain is an important factor affecting the inhibitory effect by molecular dynamics. Fang et al 27 studied the anti-agglomerant mechanism of surfactant by molecular dynamics; this study includes two main aspects: the spontaneous adsorption of surfactant on the hydrate surface and the weakening of the liquid bridge strength between hydrate particles. Molecular simulation also plays an important role in the study of the physical and chemical properties of asphalt.…”

Section: Introductionmentioning

confidence: 99%

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Aggregation Behavior of Asphalt on the Natural Gas Hydrate Surface with Different Surfactant Coverages

Chen

et al. 2021

J. Phys. Chem. C

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The aggregation behaviors of asphalt on the hydrate surface with different surfactant coverages were studied by molecular simulations. The molecular polarity index of asphalt (10.47 kcal/mol) is higher than that of Span 80 (8.19 kcal/mol). Asphalt is easier to occupy the binding sites between Span 80 and hydrate. Asphalt mainly depends on the π–π interaction to form aggregates. The dispersion interaction up to −114.17 kcal/mol is the main factor to maintain the asphalt aggregate stability. With the increase of surfactant coverage, the polar groups of asphalt are easier to associate with each other, promoting the formation of larger asphalt self-aggregates. The self-aggregation increases the complexity of asphalt stacking, and the proportion of edge-to-face stacking types increases from 40 to 60%. When the Span 80 molecule number reaches 12, the diffusion coefficient of asphalt is only (2.31 ± 0.5) × 10–8 cm2/s. Asphalt with low diffusivity can provide new sites for hydrate nucleation. The results are helpful to understand the aggregation mechanism of asphalt on the hydrate surface. Increasing the concentration of surfactant only is not a good solution to solve blocking-pipeline problems. We need to use surfactant reasonably and give full play to the anti-agglomerant effect of asphalt itself.

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The Role of Surfactants in Gas Hydrate Management

Pandey

Karcz

Solms

2021

Petroleum Engineering

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The effect of surfactants on hydrate particle agglomeration in liquid hydrocarbon continuous systems: a molecular dynamics simulation study

Abstract: Schematic of anti-agglomeration effect of surfactants promoting gas hydrate particle dispersion.

Cited by 22 publications

References 66 publications

Structural Effects of Gas Hydrate Antiagglomerant Molecules on Interfacial Interparticle Force Interactions

Structural Effects of Gas Hydrate Antiagglomerant Molecules on Interfacial Interparticle Force Interactions

Aggregation Behavior of Asphalt on the Natural Gas Hydrate Surface with Different Surfactant Coverages

The Role of Surfactants in Gas Hydrate Management

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