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OS3C-7：HYDRATE-OIL INTERFACIAL TENSION INVESTIGATION FROM MICROMECHANICAL FORCE STUDIES
发布时间:2014-07-28
Zachary M. AMAN 1,2, OLCOTT Kyle1, PFEIFFER Kristopher1, SLOAN E. Dendy1, SUM Amadeu K.1, KOH Carolyn A.1
1. Center for Hydrate Research, Chemical and Biological Engineering Department, Colorado School of Mines, UNITED STATES; 2. Centre for Energy, The University of Western Australia, AUSTRALIA
The aggregation of hydrate particles in oil-dominant systems represents a critical step in the formation of hydrate plugs. Micromechanical studies have been deployed previously to quantify the cohesive forces that bind hydrate particles, which may be dominated in the oil phase by a capillary water bridge; this capillary results in a cohesion force that may be controlled by water-oil and hydrate-oil interfacial tensions. Anti-agglomerant chemicals and natural crude oil surfactants have been shown previously to reduce water-oil interfacial tension, suggesting that they may also reduce hydrate-oil interfacial tension. In this study, we introduce a unique micromechanical force experiment, yielding an estimate for hydrate-cyclopentane interfacial tension. Hydrate cohesive forces were measured when four surfactants (arachidic acid, tripnenylacetic acid, dodecylbenzene sulfonic acid, and pyreneacetic acid) were added, separately, to the liquid hydrocarbon phase over a broad range of concentration. The results show that each surfactant reduces hydrate-oil interfacial tension, suggesting adsorption-type behavior at the hydrate interface. To complement these tests, water-oil interfacial tension was further measured using a pendant drop technique, with the same concentration levels of each surfactant. The comparative results suggest that all four surfactants adsorbed to the hydrate-oil interface at lower concentrations (10-1000×) than the water-oil interface; the greatest difference was observed with the aromatic carboxylic acids. By applying an adsorption isotherm to these data, the amount of surfactant adsorbed to each interface was estimated; the data suggest that each surfactant occupied 1.7-4.5× less space on the hydrate-oil interface than the water-oil interface. Together, these results demonstrate a unique capability of the micromechanical force methodology, and suggest that the organic acids tested here may exhibit unique adsorption-type behavior at the hydrate-oil interface.
1. Center for Hydrate Research, Chemical and Biological Engineering Department, Colorado School of Mines, UNITED STATES; 2. Centre for Energy, The University of Western Australia, AUSTRALIA
The aggregation of hydrate particles in oil-dominant systems represents a critical step in the formation of hydrate plugs. Micromechanical studies have been deployed previously to quantify the cohesive forces that bind hydrate particles, which may be dominated in the oil phase by a capillary water bridge; this capillary results in a cohesion force that may be controlled by water-oil and hydrate-oil interfacial tensions. Anti-agglomerant chemicals and natural crude oil surfactants have been shown previously to reduce water-oil interfacial tension, suggesting that they may also reduce hydrate-oil interfacial tension. In this study, we introduce a unique micromechanical force experiment, yielding an estimate for hydrate-cyclopentane interfacial tension. Hydrate cohesive forces were measured when four surfactants (arachidic acid, tripnenylacetic acid, dodecylbenzene sulfonic acid, and pyreneacetic acid) were added, separately, to the liquid hydrocarbon phase over a broad range of concentration. The results show that each surfactant reduces hydrate-oil interfacial tension, suggesting adsorption-type behavior at the hydrate interface. To complement these tests, water-oil interfacial tension was further measured using a pendant drop technique, with the same concentration levels of each surfactant. The comparative results suggest that all four surfactants adsorbed to the hydrate-oil interface at lower concentrations (10-1000×) than the water-oil interface; the greatest difference was observed with the aromatic carboxylic acids. By applying an adsorption isotherm to these data, the amount of surfactant adsorbed to each interface was estimated; the data suggest that each surfactant occupied 1.7-4.5× less space on the hydrate-oil interface than the water-oil interface. Together, these results demonstrate a unique capability of the micromechanical force methodology, and suggest that the organic acids tested here may exhibit unique adsorption-type behavior at the hydrate-oil interface.
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