(108b) Subfractionation of Asphaltenes from Brazilian Vacuum Residues

Asphaltenes from a Brazilian vacuum residue was fractionated by the IP-143 modified method, using mixtures of heptane and toluene (Heptol) as precipitation solvent. Each sub fraction was analyzed chemically, by Nuclear Magnetic Resonance and elemental analyses. Analyses by NMR shows a significant variation in nuclei that are part of the aromatic system of each sub-fraction. A-10% sub-fraction present high values of aromatic hydrogen (Har) and Carbon (Car), this show low substitution of peripheral aromatic carbons and strongly suggests extensive aromatic ring fusion. Opposite, A?20% has a low Har content, showing high substitution of peripheral aromatic carbons and lower aromatic ring fusion. The fractionation of asphaltenes using Heptol showed that the aromatic species are concentrated in the less soluble sub-fraction, as indicated by elemental analysis, and also suggests that this sub-fraction may be mainly responsible for the association of these molecules.