Auto-Emulsification of Water at Crude Oil/Water Interface: a Mechanism Driven By Osmotic Gradient

J. Duboué (1) , M. Bourrel (1) , E. Santanach Carreras (1) , A. Klimenko (1) , N. Agenet (1) , N. Passade-Boupat (1) , F. Lequeux (2)

1 TOTAL S.A.
2 SIMM - Sciences et Ingénierie de la Matière Molle (UMR 7615)

This work aims at studying the origin of spontaneous emulsification occurring at the oil/water interface. This phenomenon was observed for the five crude oils tested as well as at the interface of an asphaltene toluene mixture and water. The kinetics of appearance of water micro-droplets was slowed down for increasing salt concentrations and the micro-droplet formation ceases when the chemical potential of water they contain is equal to the one of the water in the bulk solution. Nucleation events occur at the oil-water interface and at the solid surface/liquid interface: some water micro-droplets are stuck together close to the oil/water interface, others grow in oil and sediment or nucleate at the oil/solid surface. This suggests the following mechanism: water molecules diffuse from the water reservoir into the oil phase, and then create droplets. These droplets are simultaneously fed by hydrosoluble "osmogeneous" species increasing the osmotic pressure, inducing an osmotic pumping of water molecules into micro-droplets

Domaines: Matière Molle [cond-mat.soft]

J. Duboué, M. Bourrel, E. Santanach Carreras, A. Klimenko, N. Agenet, et al.. Auto-Emulsification of Water at Crude Oil/Water Interface: a Mechanism Driven By Osmotic Gradient. Energy & Fuels, 2019, 33 (8), pp.7020-7027. ⟨10.1021/acs.energyfuels.9b00946⟩. ⟨hal-02392447⟩