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Open AccessArticle

Asphaltenes at Oil/Gas Interfaces: Foamability Even with No Significant Surface Activity

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CNRS, Sciences et Ingénierie de la Matière Molle, ESPCI Paris, PSL Research University, Sorbonne Université, 75005 Paris, France
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Laboratoire Physico-Chimie des Interfaces Complexes, ESPCI, 10 rue Vauquelin, 75005 Paris, France
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Bâtiment CHEMSTARTUP, Route Départementale 817, 64170 Lacq, France
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Total S.A., 64170 Lacq, France
*
Author to whom correspondence should be addressed.
Colloids Interfaces 2019, 3(1), 2; https://doi.org/10.3390/colloids3010002
Received: 4 December 2018 / Revised: 18 December 2018 / Accepted: 19 December 2018 / Published: 21 December 2018
In the oil industry, oil foams can be found at different steps from the crude oil treatment to the gas stations. Their lifetime can sometimes reach several hours and be much longer than the residence times available for gas/liquid separation. However, the conditions of formation and stability of such foams have been poorly studied in the literature, in contrast to the foamability of aqueous systems. On the fields, it is currently observed that crude oils enriched with asphaltenes form particularly stable foams. In this work, we have studied the influence of asphaltenes on the foamability of oil mixtures. All the experiments were performed on model systems of crude oils, that-is-to-say decane/toluene mixtures containing asphaltenes at concentrations ranging from 0.01 to 5 wt%. We in particular demonstrate that, within the investigated concentration range, asphaltenes from two different wells do not have any significant surface active properties despite their contribution to the foamability of oil mixtures. We show that the formation of an asphaltene layer at the interface with air that has been evidenced in the past results from solvent evaporation. Using a recently developed experiment based on the Marangoni effect with our model oils, we demonstrate that asphaltenes are not surface active in those oils. We further characterize the oil foamability by measuring the lifetime of the foam formed by blowing nitrogen through the liquid in a column. At concentrations larger than 1 wt%, asphaltenes significantly enhance the foamability of the oil mixtures. Moreover, the closer the asphaltenes are to their limit of precipitation the larger the foamability. However, we evidence that the oil mixtures themselves foam and we show the importance to consider that effect on the foamability. In addition, we observe that the foamability of the asphaltenes solutions unexpectedly varies with the initial height of the liquid in the column. We suggest that, although not significantly modifying the surface tension, the asphaltenes could be trapped at the oil/gas interface and thus prevent bubble coalescence. View Full-Text
Keywords: asphaltenes; foamability; layer formation; evaporation; oil foam; bubble lifetime asphaltenes; foamability; layer formation; evaporation; oil foam; bubble lifetime
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Arangalage, M.; Gingras, J.-P.; Passade-Boupat, N.; Lequeux, F.; Talini, L. Asphaltenes at Oil/Gas Interfaces: Foamability Even with No Significant Surface Activity. Colloids Interfaces 2019, 3, 2.

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