We conducted molecular dynamics (MD) simulations to investigate the effect of supercritical carbon dioxide (sc-CO₂) on the interfacial and transport properties of water–oil systems. The oil phase was resembled by employing different binary hydrocarbons (paraffin + aromatic), namely, benzene + hexane, benzene + octane, xylene + hexane, and xylene + octane. Furthermore, we added an asphaltene to the system composed of xylene and hexane to study the interfacial behavior of the heaviest fraction of oil (asphaltene) in the presence of CO₂. The simulations were performed under the operating conditions of 100 bar and 350 K. The results showed that aromatics, CO₂, and asphaltenes accumulated at the interface at low CO₂ mole fractions (x_CO2). However, when x_CO2 increased, it displaced the aromatics away from the interface and toward the bulk. At very high x_CO2, the aromatics accumulated at the oil bulk. Similarly, asphaltene molecules stacked at the interface at low x_CO2, and as x_CO2 increased, some of the asphaltene molecules dissolved and aggregated in the oil bulk. CO₂ forms a film between water and oil phases, and as the thickness of the film increases, it displaces the hydrocarbons away from the interface. The addition of sc-CO₂ diluted the interface, formed hydrogen bonds (H bonds) with water, which stabilize the CO₂ film, and reduced the interfacial tension in all systems. Furthermore, the addition of sc-CO₂ increased the diffusivity of the oil phase in all systems. However, it significantly affected the diffusivity of systems that have less polar aromatics.

中文翻译：

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CO ₂对水/二元和沥青质油的界面和传输性质的影响：分子动力学的见解

我们进行了分子动力学（MD）模拟，以研究超临界二氧化碳（sc-CO ₂）对水-油系统的界面和输运特性的影响。通过使用不同的二元烃（石蜡+芳烃），即苯+己烷，苯+辛烷，二甲苯+己烷和二甲苯+辛烷，类似于油相。此外，我们在由二甲苯和己烷组成的系统中添加了沥青质，以研究在CO ₂存在下最重油（沥青质）的界面行为。在100 bar和350 K的工作条件下进行了模拟。结果表明，芳烃，CO ₂和沥青质在低CO ₂摩尔分数下聚集在界面上（x _{CO 2}）。但是，当x _{CO 2}增加时，它将芳烃从界面移向本体。在非常高的x _{CO 2浓度下}，芳烃会积聚在机油中。类似地，沥青质分子在低x _{CO 2}处堆积在界面处，并且随着x _{CO 2的}增加，一些沥青质分子溶解并聚集在油料中。CO ₂在水和油相之间形成一层膜，并且随着膜厚的增加，它会将碳氢化合物从界面上移走。添加sc-CO ₂稀释界面，与水形成氢键（H键），从而稳定CO ₂膜，并降低所有系统中的界面张力。此外，sc-CO _2的添加增加了所有系统中油相的扩散率。但是，它极大地影响了极性芳烃较少的体系的扩散性。