Lina Constanza Navarro Quintero, Escola de Quimica, Universidade Federal do Rio de Janeiro, Ilha do Fundão. Centro de Tecnologia. Bloco I sala 224, Rio de Janeiro, 21.949-900, Brazil, Peter Rudolf Seidl, Escola de Química, UFRJ, Cidade Universitária, Rio de Janeiro, Brazil, Ljubica Tasic, Instituto de Quimica, Universidade de Campinas, Campinas, Brazil, Katia Leal, Instituto de Quimica, Universidade Federal Fluminense, Niteroi, 24020-150, Brazil, and Sonia M. C. Menezes, Chemistry, Petrobras/Cenpes, Ilha do Fundão - Quadra 7, Cidade Universitária, 21949-900 - Rio de Janeiro, RJ, Brazil.
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.