AVALIAÇÃO DA METODOLOGIA DE DETERMINAÇÃO DO INICIO DA PRECIPITAÇÃO DOS ASFALTENOS EM PETRÓLEOS UTILIZANDO FT-NIR

Abstract

The starting point of precipitation of asphaltenes, IP, is defined as the minimum amount of precipitant, in general n-heptane added to oil to the occurrence of precipitation of asphaltenes. It is observed that this phenomenon is related to kinetic factors inherent in the system, fact not previously measured in models of behavior of asphaltenes. In this context, the abundantly used technique for determining the onset of precipitation of asphaltenes using NIR spectroscopy is investigated. Are demonstrated significant amounts of additional information about using this technique, for example, the effect of the rate of addition of n-heptane to oil. This work used two samples of oil named P1 and P2, with different physical and chemical characteristics, which provides that the IP values ranged from 2.59 to 3.25 and 0.56 to 1.2 ml of heptane / g of oil, respectively, depending on the flow used. From the data obtained, it was possible to establish a standard procedure that minimizes significantly the measurement variation due to the dilution rate. This analysis therefore provides the equilibrium condition required for the correct measure of the onset of asphaltene precipitation, providing clues to a better understanding of the frequent disagreements reported in the literature. Aiming to better characterize this phenomenon, it is a comparison between two techniques well diffused in the literature, namely, optical microscopy and NIR spectroscopy. It is observed that both techniques are equivalent with respect to determining the point of beginning of precipitation of asphaltenes indicating that sometimes disagreements trial may be associated with only the choice of experimental parameters. Moreover, in general, are given some recommendations on this type of experiment.