ABSTRACT

Coarse-grained molecular dynamics simulations were used to investigate the aggregation of asphaltene and resin molecules in oils and their deposition to oil–water interfaces. Resin, “interfacially-active” asphaltenes, and “bulk-like” asphaltenes are considered as solutes in organic phases consisting of aromatics or saturates. Resins and asphaltenes formed aggregates with a spacing of 0.46 nm between stacked polycyclic sheets. Whether in the aromatic or saturated solvent, resin molecules did not interact with the interface, but its aggregates remained in the bulk. The degree of surface activity of asphaltenes was found to increase with the polarity of their chemical groups, and decrease with the aromatics content of the solvent. Axial stress profiles were measured to calculate the interfacial tension of each system. The tension of interfaces of crude oil with water was found to depend on aromatics content. The free energy of deposition of asphaltenes and resin molecules to the interface was measured using well-tempered metadynamics, in which it was found that “interfacially-active” asphaltenes possess greater stability at the oil-water interface than “bulk-like” asphaltenes, and the organic solvent influences the favorability of deposition.

摘要

粗粒度的分子动力学模拟用于研究油中沥青质和树脂分子的聚集及其在油水界面中的沉积。树脂，“界面活性”沥青质和“块状”沥青质被认为是由芳烃或饱和烃组成的有机相中的溶质。树脂和沥青质形成的聚集体在堆叠的多环片之间间隔为0.46 nm。不论是在芳族溶剂还是饱和溶剂中，树脂分子都不会与界面相互作用，但其聚集体仍保留在主体中。发现沥青质的表面活性程度随其化学基团的极性而增加，而随溶剂中芳族化合物的含量而降低。测量轴向应力曲线以计算每个系统的界面张力。发现原油与水的界面张力取决于芳族化合物含量。沥青质和树脂分子在界面上沉积的自由能是通过良好调解的动力学来测量的，其中发现“界面活性”沥青质在油水界面的稳定性要高于“本体”沥青质，有机溶剂影响沉积的有利性。