Asphaltenes are a class of high molecular weight aromatic compounds found in crude oil. They adsorb onto toluene-water interfaces and induce a spontaneous emulsification phenomenon, whereby stable water-in-oil emulsions form without the need of an external energy input. This work aims to control and understand the factors affecting spontaneous droplet formation in the presence of asphaltene adsorption. This is particularly useful for crude oil refining, where the presence of a stable emulsion hampers the efficiency of downstream processing operations. We explore the effect of the addition of copolymers designed as crude oil flow improvers as a means to control the extent of emulsion formation. We find that the polymers competitively adsorb onto the toluene-water interface and diminish spontaneous emulsification. We also conduct fluorescence microscopy experiments and measurements of the interfacial energy to determine the mechanism of spontaneous emulsification in asphaltene systems. We conclude that an emulsion forms via the diffusion of molecular water into the oil phase and subsequent binding with asphaltene aggregates, leading to the nucleation of micrometer-sized water droplets. We find that the polymer forms complexes with the dissolved asphaltenes, possibly hampering the ability of diffused water to bind to the asphaltenes and reducing the extent of spontaneous emulsification. Finally, we investigate the role of interfacial shear and dilatational viscoelasticity to better understand which fundamental interfacial properties are important in the emulsification of asphaltene-laden systems. We find that the rate of formation of an interfacial microstructural network is inversely correlated with the extent and rate of spontaneous emulsification.

中文翻译：

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沥青质诱导的自发乳化：界面共吸附和粘弹性的影响

沥青质是原油中发现的一类高分子量芳族化合物。它们吸附在甲苯-水界面上并引发自发乳化现象，从而在不需要外部能量输入的情况下形成稳定的油包水乳液。这项工作旨在控制和了解在沥青质吸附存在下影响自发液滴形成的因素。这对于原油精炼特别有用，因为稳定乳液的存在会妨碍下游加工操作的效率。我们探索了添加设计为原油流动改进剂的共聚物作为控制乳液形成程度的方法的效果。我们发现聚合物竞争性地吸附在甲苯-水界面上并减少自发乳化。我们还进行了荧光显微镜实验和界面能测量，以确定沥青质体系中自发乳化的机制。我们得出结论，乳液通过分子水扩散到油相中形成，随后与沥青质聚集体结合，导致微米级水滴的成核。我们发现聚合物与溶解的沥青质形成复合物，这可能会阻碍扩散水与沥青质结合的能力并降低自发乳化的程度。最后，我们研究了界面剪切和膨胀粘弹性的作用，以更好地了解哪些基本界面特性在含沥青质系统的乳化中很重要。