A Study of Interactions of Asphaltenes in Organic Solvents Using Surface Forces Apparatus.

摘要

A Surface Forces Apparatus (SFA) was used in this study to investigate the fundamental surface forces in oil sand processing research. Asphaltene coated surfaces were chosen as the research topic due to the critical role of asphaltenes in oil sands processing, from bitumen extraction, froth treatment to tailings treatment.;The results show that the surface interactions of asphaltenes strongly depend on types of surrounding solvents or vapours, contact time, load (pressure) and adsorption time to supporting substrate. Bridging adhesion forces were measured between one asphaltene surface and one mica surface in both pure toluene and heptane, as well as between two asphaltene surfaces in heptane. While small bridging adhesion was observed for two asphaltene surfaces in pure toluene, it changed to pure repulsion with increasing interaction time. The AFM imaging showed different degree of conformation and morphology changes with time of dip-coated asphaltene thin films in toluene and heptane, which facilitated interpretations of the results from the SFA force measurements. The results obtained from this thesis study have provided an insight into the basic interactions and dynamic nature of asphaltenes in organic media and hence in crude oils and bitumen production.;To mimic the real surface state in industry processing, dip-coated asphaltene surfaces were prepared for surface force experiments. In this study, a SFA 2000 was used to determine intermolecular and surface forces of asphaltene in organic solvents (toluene and heptane). The force vs. distance curves, or so-called force profiles obtained provide valuable information on local material properties such as interaction energies, molecular conformation changes of the interacting asphaltene surfaces or films. Atomic force microscopy (AFM) was used to provide complementary information on the surface morphology of the prepared asphaltene surfaces.