Isolation and Characterization of Interfacially Active Molecules from Asphaltene and Maltene Fractions
Year: 2023
Journal: Energy & Fuels, Volume 37, 2023-07-20
Authors: Silva, Jarlene da C.; Souza, Lindamara M.; Fonseca, Victor R.; Romão, Wanderson; Loh, Watson; Lucas, Elizabete F.
The identification of petroleum molecules or classes of molecules that stabilize water-in-oil emulsions is essential for the development of efficient methods for the treatment of emulsified systems. The formation of an interfacial film has been mainly attributed to asphaltenes, but some studies have identified other molecules that contribute to the stabilization of these emulsions. As a result of the complexity of petroleum, the molecules that act at the water–oil interface have not yet been comprehensively identified. The aim of this work was to obtain fractions of interfacially active (IA) and non-interfacially active (NIA) molecules of maltenes (IA-M) and asphaltenes (IA-A and NIA-A) extracted from a sample of asphaltic petroleum, which were compared to the IA fraction isolated from the same petroleum sample (IA-P). The samples were characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance, elemental analysis, and atmospheric pressure photoionization Fourier transform ion cyclotron resonance mass spectrometry, along with analysis of the behavior at the brine–heptol interface. The comparison of the fractions IA-M, IA-A, and NIA-A to the fraction IA-P indicated the presence of species of both maltenes and asphaltenes at the water–oil interface. Mass spectrometry revealed that the N[H] species was most abundant in the oil, followed by asphaltenes, maltenes, and NIA-A. In fraction IA-P, the most abundant species were N4 and N4O, which were more concentrated in fractions IA-A and IA-M. Some species present in the IA-P fraction were detected with greater abundance in fractions IA-M, IA-A, and NIA-A but were not detected or were only detected with low abundance in maltenes and asphaltenes, such as N2O2[H], N3O2, N4O2, and N4OS classes, probably as a result of the greater selectivity of the technique used in this work to separate fractions containing molecules with narrower polarity distribution. These results indicate the importance of performing studies with subfractions of petroleum extracted by methods based on adsorption at the water/oil interface to produce more direct information on the role of oil components that act on the formation and stabilization of their emulsified systems.
