Étude de la structure des solutions asphalténiques et d'un résidu sous vide Safaniya

Abstract : We have examined a Safaniya Vacuum Re sidue (VR) and its fraction s (asphaltenes, resins, aromatics and saturates). ln order to describe the macrostructure of these cornplex colloidal systems, we used different characterisation techniques : small angle X-ray and neutron scattering (SAXS and SANS), rheology and electron microscopy. Scattering techniques allows us to precise the model for asphaltenes and resins in solution. These macromolecules are polydisperse disk-like particles with thickness and diameter which are respectively close to 1 and 10 nm. The average molecular weight is equal to 106 000 for asphaltenes and 3 300 for resins. We have shown that SAXS is more sensitive to the scattering of the aromatic part of the molecule. Adding n-heptane induces first a desolvation of the molecules and then an aggregation up to f flocculation. These solutions present large heterogeneities due to concentration fluctuations . A huge difference in the chemical composition of the different asphaltene molecules can explain these fluctuations. These heterogeneities are stable as a function of temperature; this means that exist strong molecular interactions. Ultracentrifugation gives two different fractions which contain different chemical structures. more or less aromatic. Solutions, in good solvent, of these two fractions are homogeneous but a mixture of these two fractions exhibits heterogeneities. SAXS gives information about the structure of VR. We have observed the presence of large density fluctuations up to 300°C. Rheological measurements confirm threedimensional organisation.
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http://docnum.univ-lorraine.fr/prive/SCD_T_1996_0049_GUILLE.pdf
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Submitted on : Thursday, March 29, 2018 - 10:55:29 AM
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Véronique Guille. Étude de la structure des solutions asphalténiques et d'un résidu sous vide Safaniya. Autre. Université Henri Poincaré - Nancy 1, 1996. Français. ⟨NNT : 1996NAN10049⟩. ⟨tel-01747238⟩

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