Solvent Effects on the Structure of Petroleum Asphaltenes
Solvent Effects on the Structure of Petroleum Asphaltenes
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溶剂对石油沥青质结构的影响
DOI：
10.1021/acs.energyfuels.1c01851
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发表时间：
2021
期刊：
影响因子：
5.3
通讯作者：
Hoepfner, Michael P.
中科院分区：
文献类型：
--
作者：
Yang, Yuan;Headen, Thomas F.;Zhang, Jingzhou;Hoepfner, Michael P.
采用中子全散射研究溶剂对沥青质行为的影响，通过比较固相样品与分散在1-甲基萘（1-MN）中的样品的结构解释作为温度和沥青质溶解度的函数。这种强大的技术使结构的解释范围从本地分子秩序的长度尺度上形成的纳米聚集体和/或分形集群在一个单一的实验。我们观察到，更不稳定的沥青质表现出更大的芳族堆积在当地的分子长度尺度上，也产生更频繁的纳米级协会。然而，当温度升高时，较大的沥青质簇的分裂与沥青质侧链相互作用程度的降低相关。此外，分散的沥青质表现出增加芳香堆积的温度升高，这表明由溶剂消耗相互作用驱动的组装的熵驱动力。这一观察结果在沥青质科学中是新颖的，并作为一种途径来评估局部溶剂组合物对双折射和熵组装途径的影响。结果表明，虽然更不稳定的沥青质表现出更大的芳族堆积，进一步的协会可能有助于增加无序的侧链相互作用。实验结果也作为一个有用的基准，以验证模拟预测的沥青质结构。
Neutron total scattering was employed to study the impact of a solvent on the behavior of asphaltenes by comparing structural interpretations of solid phase samples to those dispersed in 1-methylnaphthalene (1-MN) as a function of temperature and asphaltene solubility. This powerful technique enables structural interpretation on length scales ranging from local molecular order to the formation of nanoaggregates and/or fractal clusters in a single experiment. We observed that more unstable asphaltenes exhibit greater aromatic stacking on the local molecular length scale and also produce more frequent nanometer-sized associations. However, when the temperature was elevated, the breakup of larger asphaltene clusters was correlated to a reduction in the extent of asphaltene side-chain interactions. Additionally, dispersed asphaltenes demonstrated an increase in aromatic stacking as the temperature was increased, suggesting an entropic driving force for assembly driven by solvent depletion interactions. This observation is novel in asphaltene science and serves as a pathway to assess the impact of local solvent composition on both enthalpic and entropic assembly pathways. The results suggest that while more unstable asphaltenes exhibit greater aromatic stacking, further association may be assisted by an increase in the disordered side-chain interactions. The experimental results also serve as a useful benchmark to validate simulation predictions of asphaltene structure.