Study of Asphaltenes Structure and their Aggregation Properties

Petroleum has been used by civilization since a long time ago and its importance has grown with time. Its greatest use is as an energy source, in addition to being used as feedstock in the manufacture of other inputs. Due to its being a complex mixture it is necessary to refine the crude oil. Some organic compounds can precipitate during this process and generate clogging inside the pipelines, raising the production costs, becoming a concern.

Asphaltenes are one of the responsible for the occurrence of precipitation along the entire oil production chain. This class of compounds can present two types, island and archipelago; a better understanding of their structures is required to predict their behavior in the precipitation process. Thus, studies of asphaltenes using spectroscopy analysis are increasing.

In this work, spectroscopic techniques such as FTIR, raman and nuclear magnetic resonance were applied to four asphaltenes, two from stable oils (AP2 and AP4) and two from unstable oils (AP1 and AP3). The values obtained from Raman showed a larger size of the aromatic nucleus for the asphaltene AP3. FTIR analysis indicated a high polarity for the unstable asphaltenes. The data obtained from 1H NMR spectra, showed a lower amount of aromatic hydrogens for AP1, corroborating the results of aromaticity from FTIR. For stable asphaltene AP2, it was observed a smaller substitution in the aromatic core and a larger amount of hydrogens in the aliphatic chain. With this information, it is possible to correlate the aggregation behavior of asphaltenes through the interaction between their structures given by the higher aromaticity, polarity and the aromatic core.

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The authors would like to thank Labpetro, CAPES, CNPq, FAPES and PETROBRAS-CENPES.