Estudo da estrutura de asfaltenos e suas propriedades de agregação

Abstract

Since petroleum began to be used on a commercial scale, it has been an essential material for civilization. Its greatest use as an energy source, in addition to being used as feedstock in the manufacture of other inputs, requiring refining processes. The precipitation of organic compounds can generate an increase in production costs, becoming a worldwide concern in the oil industry. Asphaltenes are responsible for the occurrence of precipitation along the entire oil production chain. The literature presents works using analytical techniques to understand the structure of the asphaltenes in the precipitation process. For this purpose, spectroscopy techniques such as infrared (IR), raman and nuclear magnetic ressonance (NMR) were applied in four asphaltenes from two stable oils (AP2 and AP4) and two stable oils (AP1 and AP3), one of them is classified as a heavy (ºAPI 13,5) and the other three as light (ºAPI 41,6; 39,5; 32,6). The values obtained from Raman spectroscopy indicated a larger size of the aromatic nucleus for the asphaltene AP3 (unstable) compared to the other asphaltenes. Through the FTIR analysis, it is observed a higher polarity for the unstable asphaltenes (AP1 and AP3) and also a higher polarity for the asphaltene AP1. The data obtained from the 1H NMR spectra, showed a lower amount of aromatic hydrogens for AP1, corroborating the results of aromaticity from FTIR. For stable asphaltenes 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.