Abstract
ABSTRACT Thermal Field Flow Fractionation (ThFFF) was used to determine the molecular weight average (Mw) and distribution of Venezuelan crude asphaltenes. Thermophoretic mobility (DT) was determined as a measure of transport characteristics. The experiments were performed in tetrahyrofurane (THF) and toluene (TOL), as well as with the addition of a dispersion agent to these solvents. Polystyrene standards were run under the same conditions for system calibration Results indicate that differences among asphaltenes from different crudes, or the same asphaltene kept under different conditions, can be qualitatively observed in the fractograms, or quantitatively from ThFFF data (Mw, Mn, Mz, molecular weight distribution and DT), in different solvents. Even though this study was not conducted to elucidate the mechanism of the dispersion agent, it could be found that a second factor, analogous to a secondary chemical equilibrium studied in sedimentation FFF can be introduced in ThFFF to expand its applicability to relative small molecules and/or aggregates, in complex structures like asphaltenes.
Published Version
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