Toward mechanistic understanding of asphaltene aggregation behavior in toluene: The roles of asphaltene structure, aging time, temperature, and ultrasonic radiation
Toward mechanistic understanding of asphaltene aggregation behavior in toluene: The roles of asphaltene structure, aging time, temperature, and ultrasonic radiation
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DOI：
10.1016/j.molliq.2018.04.061
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发表时间：
2018-08-15
影响因子：
6
通讯作者：
Husein, Maen M.
中科院分区：
文献类型：
--
作者：
Hemmati-Sarapardeh, Abdolhossein;Dabir, Bahram;Husein, Maen M.
为了更好地了解沥青质在适当溶剂（例如甲苯或天然介质）中的胶态状态，已经进行了许多研究。尽管进行了这些尝试，但沥青质聚集的机制及其对沥青质分子结构的依赖性尚未完全了解。在本研究中，使用元素分析和能量色散 X 射线光谱 (EDX)、扫描电子显微镜 (SEM)、漫反射傅里叶变换红外光谱 (DRIFTS) 和 X 射线衍射 (XRD) 对三种不同类型的沥青质（即沥青质 A、沥青质 B 和沥青质 C）进行了表征。然后，使用动态光散射（DLS）来测量甲苯中沥青质聚集体的尺寸。研究了沥青质结构、组成、浓度、温度、超声辐射和老化时间对沥青质聚集行为的影响。结果表明，随着甲苯中沥青质浓度的增加，观察到沥青质聚集体尺寸略有增加。此外，沥青质聚集体的尺寸很大程度上取决于沥青质的结构和组成。沥青质 C 具有最低的芳香性、极性（杂原子）和每个沥青质片中稠合环的数量，显示出最低的聚集体尺寸。极性和芳香性在沥青质不稳定性或聚集体尺寸中起着关键作用。与沥青质B相比，具有更高极性和更多官能团但芳香性较低的沥青质A表现出更高的聚集体尺寸。此外，老化时间可以显着增加沥青质聚集体的尺寸，从老化时间15分钟后的几纳米到1个月后的几微米。此外，超声波辐射可以将沥青质聚集体的尺寸减小到最佳值。此外，随着温度升高，沥青质聚集体尺寸由于溶解度增加而减小。 (C) 2018 Elsevier B.V. 保留所有权利。
Many investigations have been carried out to provide a good understanding of the colloidal state of asphaltenes in appropriate solvents such as toluene or natural medium. Despite these attempts, the mechanism of asphaltene aggregation and its dependency on the structure of asphaltene molecules has not been fully understood yet. In this study, three different types of asphaltenes, namely asphaltene A, asphaltene B, and asphaltene C, were characterized using elemental analysis and energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS), and X-ray diffraction (XRD). Then, dynamic light scattering (DLS) was used to measure the size of asphaltene aggregates in toluene. The effects of asphaltene structure, composition, concentration, temperature, ultrasonic radiation and aging time on the aggregation behavior of the asphaltenes were investigated. The results show that as asphaltenes concentration in toluene increases, a slight increase in asphaltene aggregates size is observed. In addition, the size of asphaltene aggregates strongly depends on asphaltenes structure and composition. Asphaltene C, which has the lowest aromaticity, polarity (heteroatoms), and number of fused rings in each asphaltene sheet shows the lowest aggregates size. Both polarity and aromaticity play key roles in asphaltene instability or aggregates size. Asphaltene A with higher polarity and more functional groups but lower aromaticity displays a higher aggregates size compared with asphaltene B. Furthermore, aging time can significantly increase the size of asphaltene aggregates from few nanometers after 15 min aging time to few microns after 1 month. Moreover, ultrasonic radiation can decrease the size of asphaltene aggregates down to an optimum value. Furthermore, with increasing temperature, asphaltenes aggregate size decreases due to increasing solubility. (C) 2018 Elsevier B.V. All rights reserved.