Ali Azeezat, Cole David R, Striolo Alberto
Department of Chemical Engineering, University College London, London WC1E 6BT, United Kingdom.
School of Earth Sciences, The Ohio State University, Columbus, Ohio 43210, United States.
Energy Fuels. 2023 Jul 28;37(16):11662-11674. doi: 10.1021/acs.energyfuels.3c00504. eCollection 2023 Aug 17.
The solubility of asphaltenes in hydrocarbons changes with pressure, composition, and temperature, leading to precipitation and deposition, thereby causing one of the crucial problems that negatively affects oil production, transportation, and processing. Because, in some circumstances, it might be advantageous to promote asphaltene agglomeration into small colloidal particles, molecular dynamics simulations were conducted here to understand the impacts of a chemical additive inspired by cyclohexane on the mechanism of aggregation of model island and archipelago asphaltene molecules in toluene. We compared the results in the presence and absence of a kaolinite surface at 300 and 400 K. Cluster size analyses, radial distribution functions, angles between asphaltenes, radius of gyration, and entropic and energetic calculations were used to provide insights on the behavior of these systems. The results show that the hypothetical additive inspired by cyclohexane promoted the aggregation of both asphaltenes. Structural differences were observed among the aggregates obtained in our simulations. These differences are attributed to the number of aromatic cores and side chains on the asphaltene molecules as well as to that of heteroatoms. For the island structure, aggregation in the bulk phase was less pronounced than that in the proximity of the kaolinite surface, whereas the opposite was observed for the archipelago structure. In both cases, the additive promoted stacking of asphaltenes, yielding more compact aggregates. The results provided insights into the complex nature of asphaltene aggregation, although computational approaches that can access longer time and larger size scales should be chosen for quantifying emergent meso- and macroscale properties of systems containing asphaltenes in larger numbers than those that can currently be sampled via atomistic simulations.
沥青质在烃类中的溶解度会随压力、成分和温度而变化，从而导致沉淀和沉积，进而引发对石油生产、运输和加工产生负面影响的关键问题之一。由于在某些情况下，促进沥青质聚集成小的胶体颗粒可能具有优势，因此在此进行了分子动力学模拟，以了解受环己烷启发的化学添加剂对甲苯中模型岛状和群岛状沥青质分子聚集机制的影响。我们比较了在300 K和400 K下有无高岭土表面时的结果。通过簇尺寸分析、径向分布函数、沥青质之间的夹角、回转半径以及熵和能量计算，来深入了解这些系统的行为。结果表明，受环己烷启发的假想添加剂促进了两种沥青质的聚集。在我们的模拟中获得的聚集体之间观察到了结构差异。这些差异归因于沥青质分子上芳香核和侧链的数量以及杂原子的数量。对于岛状结构，本体相中的聚集不如高岭土表面附近明显，而对于群岛状结构则观察到相反的情况。在这两种情况下，添加剂都促进了沥青质的堆积，产生了更紧密的聚集体。尽管应该选择能够访问更长时间和更大尺寸尺度的计算方法来量化含有比目前通过原子模拟能够采样数量更多的沥青质的系统的新兴介观和宏观性质，但这些结果为沥青质聚集的复杂性质提供了见解。
