SIMULATION OF THE INTERACTIONS BETWEEN ASPHALTENES AND SOLVENT BY MOLECULAR DYNAMICS

Peter R. Seidl¹, Alexandre N. M. Carauta² and Júlio C. G. Corrêia³.

1. Departamento de Processos Orgânicos, Escola de Química, Universidade Federal do Rio de Janeiro - UFRJ. Rio de Janeiro – RJ. Brazil.

2. Departamento de Química Inorgânica. Instituto de Química. Universidade Federal Fluminense – UFF. Niterói – RJ. Brazil.

3. Coordenação de Apoio a Pequena e Média Empresa do Centro de Tecnologia Mineral – CETEM. Rio de Janeiro – RJ.

Molecular mechanics and dynamics have played an important role in the investigation of association phenomena of asphaltene aggregates and the way it is affected by different solvents. In order to better understand the role of solvents in fractionating asphaltenes extracted from vacuum residues and evaluate their effects under different conditions we modeled the effect of solvent and solvent mixtures on asphaltene aggregates formed by representative asphaltene molecules. Molecular dynamics simulations were run on asphaltene aggregates after minimizing the conformation of each molecule and verifying the most stable position for docking. They reveal the extent that these solvents are able to separate the aggregate at different temperatures after a given period of time. Results have shown that, the two extremes for solubility are well characterized: in n-heptane the distance between monomers hardly changes, reflecting the almost negligible effect of the solvent on the aggregate; on the other hand, in toluene this distance increases to over 5.00 Å suggesting a dissociation process. The behavior in n-butane and isobutane falls between these two extremes. The effect of 1:1 butane-isobutane mixture is not as good as one for the isolated solvents.