Asphaltenes at the water-oil interface using DPD/COSMO-SAC
FC De Oliveira and JM Maia and FW Tavares, COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS, 625, 126828 (2021).
Asphaltenes are the heaviest fraction of crude oil. Its deposition causes large problems during oil exploitation. Sometimes it is difficult to separate the asphaltenes from the oil because of the very stable water in oil emulsions that they form. The Dissipative Particle Dynamics (DPD) has been used to study the interfacial properties of asphaltene molecules at the water-oil interface. The COSMO-SAC method was used to systematically obtaining the conservative force DPD parameters. The methodology to obtain the DPD-parameters has been tested in hydrocarbon- water systems yielding good results for the interfacial tension compared to experimental data. Asphaltene-toluene mixtures were also analyzed using this methodology in terms of diffusion coefficients and structural information showing consistent results. Ultimately, the water- asphaltene-oil systems were investigated, and the critical micelle concentration is in agreement with experimental values. Density profiles and angular analysis of asphaltene molecules at the water-oil interface have also been carried out, showing that those molecules are preferentially parallel to the interface at low asphaltene concentration, whereas at higher concentrations, entropic effects become dominant, and the molecules assume a tilted configuration. The size and number of aggregates at the water-oil interface show that asphaltenes form small aggregates at low concentrations and large structures at high concentrations.
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