Liu Fang, Darjani Shaghayegh, Akhmetkhanova Nelya, Maldarelli Charles, Banerjee Sanjoy, Pauchard Vincent
Energy Institute, ‡Department of Chemical Engineering, and §Levich Institute, City College of New York , New York, New York 10031, United States.
Langmuir. 2017 Feb 28;33(8):1927-1942. doi: 10.1021/acs.langmuir.6b03958. Epub 2017 Feb 10.
Asphaltenes are a solubility class of crude oils comprising polyaromatic and heterocyclic molecules with different interfacial activities. The previously neglected effects of compositional mixture on dilatational rheology are discussed in the light of diffusional relaxation models. It is demonstrated that the reported deviations from the Lucassen-van den Tempel model for a single-component solution could largely originate from a distribution in adsorption coefficients within the asphaltenes class. This particularly applies to the peculiar gel point rheology previously ascribed to asphaltenes cross-linking at the interface. Furthermore, an extensive bibliographical review shows that asphaltenes dilatational rheology data always verify the main features of diffusional relaxation, including a decrease in modulus at high bulk concentrations and phase shift values always lower than 45°. Using diffusional relaxation concepts, the reanalysis of the most extensive dataset so far confirmed recently published studies, showing that asphaltenes exhibit a unique equation of state (EOS) irrespective of adsorption conditions. This EOS proves to be very similar for bitumen and petroleum asphaltenes. Finally, a numerical application of a binary diffusional model proved efficient to capture both dynamic interfacial tension and dilatational rheology, with the same parameters. It appears that a minority of asphaltenes (less than 10%) have a much stronger interfacial activity than the bulk of them, as previously demonstrated by fractionation. These results open up the need for a reinterpretation of the physical mechanisms of asphaltenes adsorption in terms of classical amphiphilic behavior, with a potential impact on emulsion breaking and enhanced oil recovery strategies.
沥青质是原油中的一类可溶物，由具有不同界面活性的多环芳烃和杂环分子组成。根据扩散松弛模型，讨论了成分混合物对膨胀流变学先前被忽视的影响。结果表明，对于单组分溶液，所报道的与卢卡森 - 范登·滕佩尔模型的偏差可能很大程度上源于沥青质类中吸附系数的分布。这尤其适用于先前归因于沥青质在界面处交联的特殊凝胶点流变学。此外，广泛的文献综述表明，沥青质膨胀流变学数据始终验证扩散松弛的主要特征，包括在高本体浓度下模量的降低以及相移值始终低于45°。使用扩散松弛概念，对迄今为止最广泛的数据集进行重新分析证实了最近发表的研究，表明无论吸附条件如何，沥青质都表现出独特的状态方程（EOS）。事实证明，这种EOS对于沥青和石油沥青质非常相似。最后，二元扩散模型的数值应用证明能够有效地同时捕捉动态界面张力和膨胀流变学，且使用相同的参数。正如先前通过分馏所证明的那样，似乎少数沥青质（不到10%）具有比它们中的大多数更强的界面活性。这些结果表明需要根据经典的两亲性行为重新解释沥青质吸附的物理机制，这可能对破乳和强化采油策略产生影响。
