Figures 4 and 5 show two different regimes for SRB and only one for DAO:

1. Sequential adsorption of AS at the Bitumen/Water interface Mathieu NEUVILLE, Francis RONDELEZ -Total SA, CRES, BP 22, 69360 Solaize, France • Thierry LEMOGNE – LTDS, CNRS, 36 Avenue Guy de Collongue, 69134 Ecully, France • Alain CAGNA, Michael SANCHEZ – Teclis - IT -Concept, 69770 Longessaigne, France The essential + 2,4 + 3,5 + 0,5 By performingexperiments on straight-runbitumen(SRB) and desasphaltedoil(DAO) prepared by n-hepthane, we show thattwo types of surfactant contributeto the lowering of the interfacial tension on bitumen. These surfactants belong to the asphaltensclass [1]. • The temperature of the experiments was T = 90 °C, the acidic aqueous phase was fixed at pH = 2,7 and the time range investigated was larger than in our previous work [2]t = 0-23 000 s. Both the static (interfacial tension) and the dynamic (surface rheology) properties of the interface are simultaneously measured, allowing complete characterization of the interfacial layer. • The experiments and set up • Interfacial Tension Samples Experimentalmethods Interfacial tension and surface rheology are measured by the «tracker» drop shapeanalysistensiometer. Afterrescaling the viscosity, the evolutionissimilar. Asphaltenes come from the bulk. The adsorption kineticsiscontroled by the bulkviscosity. SRB at 7000 s, ph=2,7, T=90°C Figure 1 • Interpretation Surface elasticity and surface viscosity[3] • Figures 4 and 5 show twodifferentregimes for SRB and only one for DAO: • during the first 1400 seconds the interfacial layers formed in SRB and DAO have an indistinguishable behaviour = same surface-active molecules. • at longertimes, the macroscopic properties of the SRB and DAO interfaces are different: the surface elasticity and surface viscosity for SRB become very large =formation of a two-dimensional molecular network. The time evolution of the visco-elastic properties of the bitumen/water interface is very different in both systems. For DAO, the values at the longest times are considerably smaller than in SRB, by a factor of 5.5 for the surface elasticity and a factor of 9.1 for surface viscosity. The state of the interface can be considered as fluid in the first case and elastic in the second case. Figure 4 Figure 5 Figure 3 Figure 2 • Conclusions and perspectives In SRB, our interfacial data reveal the presence of two types of surface-active species (called A and B). The adsorption is sequential: the A-type molecules adsorb first, followed by an exchange process between the A-type and the B-type molecules at longer times. Eventually the interface gets totally covered with B-type molecules. In the case of DAO, the B-type molecules are no longer present and only the A-type surfactants contribute to the lowering of the interfacial tension. We perform in-situ X-ray photoelectron spectroscopy at the bitumen-water interface at 7000 s. We observe that 1) the SRB/air interface is not entirely composed of AS, 2) there is an enrichment in heteroatomsfor the AS adsorbing at the bitumen/water interface. SRB DAO Adsorption of surfactant of type A (for SRB and DAO) 0 Type A Type A 50 s (7 s) Type B 7 Competitive Adsorption of surfactant of type B (for SRB only) 1200 s (180 s) Pure type A Mixture of type A and B Pure type B 7000 s (1000 s) 15 Surface Pressure (mN·m-1) Time for SRB (Time for DAO) References: [1] Poteau S., Argillier JF., Energy and Fuels, 19 (2005) [2] Chaverot P., Cagna A., Glita S., Rondelez F., Energy and Fuels, 22, (2008) [3] Lucassen J., Reynders E.H., Adv. in Chem. Ser., ed. by E.D. Goddard, (1975). Figure 6 Acknowledgments: We thank the Direction Scientifique and the Direction “Marketing Bitumes” of the Total Company for their continuous interest and support of this work. We also thank the analytic department of the CReS for their expert contribution to characterizing our samples. ~ 5th World Congress on Emulsions, Lyon , October 12-14, 2010 ~