Mesoscale Aggregation of Sulfur-Rich Asphaltenes: In Situ Microscopy and Coarse-Grained Molecular Simulation
Mesoscale Aggregation of Sulfur-Rich Asphaltenes: In Situ Microscopy and Coarse-Grained Molecular Simulation
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DOI：
10.1021/acs.langmuir.2c00323
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发表时间：
2022-05-20
期刊：
影响因子：
3.9
通讯作者：
Wu, Lei
中科院分区：
文献类型：
--
作者：
Hammond, Christian B.;Aghaaminiha, Mohammadreza;Wu, Lei
沥青质聚集对许多自然和工业过程至关重要，从地下水污染和修复到石油利用。尽管在过去的几十年里进行了大量的研究，但富硫沥青质聚集的基本过程仍然没有被完全理解。在这项工作中，我们研究了由富硫沥青质形成的聚集体的颗粒对颗粒的生长，采用了显微观察和分子模拟相结合的方法。实验结果表明，由富硫沥青质组装的聚集体具有随时间变化的结构自相似性，其生长速率符合经典的反应限制聚集和扩散限制聚集之间的交叉行为。尽管使用Smoluchowski方程预测的粒径分布偏离了初始阶段的观测结果，但它提供了对后期聚集体粒径分布的合理预测，即使观测到的簇聚并对相应的簇大小分布有重要影响。模拟结果表明，脂肪族硫对沥青质纳米聚合体的形成具有非单调性影响，这取决于沥青质的分子结构。具体来说，脂肪族硫对类霜纳米聚集体的结构有深远的影响，特别是当沥青质分子具有小芳香核时。脂肪族硫与邻近分子侧链之间的相互作用解释了排斥力，这在很大程度上解释了纳米聚集体和相应胶体聚集体的多分散性。这些结果可以提高我们目前对富硫沥青质聚集复杂过程的认识，并有助于设计高效的原油利用和修复技术。
Asphaltene aggregation is critical to many natural andindustrial processes, from groundwater contamination and remediation topetroleum utilization. Despite extensive research in the past few decades, thefundamental process of sulfur-rich asphaltene aggregation still remains notfully understood. In this work, we have investigated the particle-by-particlegrowth of aggregates formed with sulfur-rich asphaltene by a combinedapproach ofin situmicroscopy and molecular simulation. The experimentalresults show that aggregates assembled from sulfur-rich asphaltene havemorphologies with time-dependent structural self-similarity, and their growthrates are aligned with a crossover behavior between classic reaction-limitedaggregation and diffusion-limited aggregation. Although the particle sizedistribution predicted using the Smoluchowski equation deviates from theobservations at the initial stage, it provides a reasonable prediction ofaggregate size distribution at the later stage, even if the observed cluster coalescence has an important effect on the correspondingcluster size distribution. The simulation results show that aliphatic sulfur exerts nonmonotonic effects on asphaltene nanoaggregateformation depending on the asphaltene molecular structure. Specifically, aliphatic sulfur has a profound effect on the structure ofrod-like nanoaggregates, especially when asphaltene molecules have small aromatic cores. Interactions between aliphatic sulfur andthe side chain of neighboring molecules account for the repulsive forces that largely explain the polydispersity in the nanoaggregatesand corresponding colloidal aggregates. These results can improve our current understanding of the complex process of sulfur-richasphaltene aggregation and sheds light on designing efficient crude oil utilization and remediation technologies.