Comparison of Interfacial Tension Reduction in a Toluene/Water System by Colombian Crude Oil and Its Interfacially Active Components

It is generally accepted that asphaltenes are the main stabilizing agents of water-in-crude-oil emulsions. However, the phenomenon of formation and stabilization of the colloid is complex and requires further studies. In this work, interfacially active species were extracted from samples of three Colombian oil fields. The asphaltenes were obtained by the Soxhlet method. Then, the interfacial material (IM) from crude oil was obtained by a recently proposed wet silica methodology. The former extraction method is based on the solubility criterion, in contrast to the latter method that allows for the acquisition of substances by their affinity with water. The materials extracted were characterized by nuclear magnetic resonance, laser desorption/ionization mass spectroscopy, Fourier transform infrared spectroscopy, and Raman spectroscopy. Finally, we evaluate the contribution of asphaltenes and IM in interfacial tension (IFT) reduction, which is one important mechanism in the formation and stabilization of emulsions. Solutions of crude oil, asphaltenes, and IM were prepared in toluene, and their effect on IFT against water was measured using pendant drop tensiometry. We found that IM extracted by the wet silica method reduces IFT considerably more than the asphaltenes. We also prepared solutions with extracted asphaltenes and crude oil and compare the IFT reduction in equivalent asphaltene concentrations. We conclude that, for one of the samples, the presence of the other fractions does not contribute to the IFT reduction and that the asphaltenes are the main surfactant in that case. In contrast, the IFT reduction caused by the non-asphaltene fraction in the other two samples was observed. We proposed this methodology to evaluate the importance of asphaltenes in the IFT alteration. The identification of the most surfactant-rich crude oil fraction can be used to choose the appropriate approach to solve water–crude oil interfacial-associated problems.