Molecular Dynamics Study on the Spontaneous Adsorption of Aromatic Carboxylic Acids to Methane Hydrate Surfaces: Implications for Hydrate Antiagglomeration
Spontaneous adsorption of aromatic carboxylic acids (phenylacetic acid, 2-napthylacetic acid, and 1-pyreneacetic acid) to the CH4 hydrate surface in both liquid hydrocarbon and aqueous phases has been investigated using molecular dynamics simulations, aiming to provide implications for hydrate antia...
| Published in: | Energy & Fuels |
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| Main Authors: | , , , , |
| Format: | Report |
| Language: | English |
| Published: |
AMER CHEMICAL SOC
2022
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| Subjects: | |
| Online Access: | http://ir.giec.ac.cn/handle/344007/36626 http://ir.giec.ac.cn/handle/344007/36627 https://doi.org/10.1021/acs.energyfuels.2c00347 |
| Summary: | Spontaneous adsorption of aromatic carboxylic acids (phenylacetic acid, 2-napthylacetic acid, and 1-pyreneacetic acid) to the CH4 hydrate surface in both liquid hydrocarbon and aqueous phases has been investigated using molecular dynamics simulations, aiming to provide implications for hydrate antiagglomeration. Simulation results indicate that the liquid-phase environment, that is, the liquid hydrocarbon phase or aqueous phase, especially its hydrophilic/hydrophobic property, could profoundly affect the interfacial structures of CH4 hydrate and the adsorption behavior of aromatic carboxylic acids. In the hydrophobic hydrocarbon phase, with many CH4 molecules dissolved, more interfacial hydrate structures decompose and form a thin quasiliquid water film on the hydrate surface; aromatic carboxylic acids act as surfactants, that is, strongly adsorb to the hydrate/hydrocarbon interface and significantly lower the interfacial tension. Moreover, they adsorb to the interfacial water film on the hydrate surface with their carboxylic groups, which may destabilize the capillary liquid bridges formed among hydrate particles and then prevent hydrate coalescence. By contrast, fewer interfacial hydrate structures decompose in the aqueous phase, as CH4 molecules rarely dissolve in water but stay at the hydrate/water interface and stabilize the hydrate solid; only a few aromatic carboxylic acids adsorb to the hydrate/water interface by inserting their aromatic rings into the semicages on the hydrate surface, which may kinetically disturb the hydrate growth. Such adsorption is not very strong and mainly depends on the size matching between aromatic rings and semicages. Consequently, many more aromatic carboxylic acid molecules strongly adsorb to the hydrate surface in the hydrocarbon phase than in the aqueous phase, which can explain why antiagglomerants generally show a higher performance in the hydrocarbon phase and easily lose efficacy at high watercuts. Additionally, the molecular structures could also affect the adsorption ... |
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