Isolation and Characterization of Interfacially Active Molecules from Asphaltene and Maltene Fractions

The identification of petroleum molecules or classesof moleculesthat stabilize water-in-oil emulsions is essential for the developmentof efficient methods for the treatment of emulsified systems. Theformation of an interfacial film has been mainly attributed to asphaltenes,but some studies have identified other molecules that contribute tothe stabilization of these emulsions. As a result of the complexityof petroleum, the molecules that act at the water-oil interfacehave not yet been comprehensively identified. The aim of this workwas to obtain fractions of interfacially active (IA) and non-interfaciallyactive (NIA) molecules of maltenes (IA-M) and asphaltenes (IA-A andNIA-A) extracted from a sample of asphaltic petroleum, which werecompared to the IA fraction isolated from the same petroleum sample(IA-P). The samples were characterized by Fourier transform infraredspectroscopy, nuclear magnetic resonance, elemental analysis, andatmospheric pressure photoionization Fourier transform ion cyclotronresonance mass spectrometry, along with analysis of the behavior atthe brine-heptol interface. The comparison of the fractionsIA-M, IA-A, and NIA-A to the fraction IA-P indicated the presenceof species of both maltenes and asphaltenes at the water-oilinterface. Mass spectrometry revealed that the N[H] species was mostabundant in the oil, followed by asphaltenes, maltenes, and NIA-A.In fraction IA-P, the most abundant species were N4 and N4O, whichwere more concentrated in fractions IA-A and IA-M. Some species presentin the IA-P fraction were detected with greater abundance in fractionsIA-M, IA-A, and NIA-A but were not detected or were only detectedwith low abundance in maltenes and asphaltenes, such as N2O2[H], N3O2,N4O2, and N4OS classes, probably as a result of the greater selectivityof the technique used in this work to separate fractions containingmolecules with narrower polarity distribution. These results indicatethe importance of performing studies with subfractions of petroleumextracted by methods based on adsorption at the water/oil interfaceto produce more direct information on the role of oil components thatact on the formation and stabilization of their emulsified systems.

Automated summary

The identification of petroleum molecules or classes that stabilize water-in-oil emulsions is crucial for efficient treatment methods. This study aimed to obtain fractions of interfacially active and non-interfacially active molecules from asphaltic petroleum samples and compare them to a fraction isolated from the same sample. Various spectroscopic and analytical techniques were used to characterize the samples, and the results indicated the presence of both maltenes and asphaltenes at the water-oil interface.