Asphaltene adsorption mechanism under shear flow probed by in situ neutron reflectivity measurements
1 IFP Énergies nouvelles, 1-4 Av. de Bois-Préau, 92852 Rueil-Malmaison Cedex, France
2 CEA-CNRS, IRAMIS, Laboratoire Léon Brillouin, 91191 Gif-sur-Yvette, France
Revised: 27 September 2012
Published online: 3 December 2012
We propose here a method to adapt a rheometer with a cone/plate geometry to a neutron reflectometer in order to perform in situ reflectivity measurements. This study allowed us to probe the influence of the shear rate on the mechanism of asphaltenes adsorption, the heaviest and most polar compounds of crude oil, using bad solvent conditions. Such experiment aims at describing at a local scale the surface modifications induced by flowing crude oils (pipe transportation or production through porous media). Without shearing, in a 34%/66% xylene/dodecane mixture for which the asphaltenes flocculation is achieved in bulk, the nanoaggregates are able to be adsorbed on a hydrophilic surface as multilayers, with a surface excess much larger than for good solvent conditions. Moreover, the thickness of these multilayers increases almost linearly with time, in accordance with QCM experiments. In shear rate conditions, the adsorption process is however strongly limited since the surface excess of the adsorbed layers is around twice lower at 2600 s−1 than at 1200 s−1.
© EDP Sciences, Springer-Verlag, 2012