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Initial stages of asphaltene aggregation in dilute crude oil solutions: studies of viscosity and NMR relaxation

机译:稀原油溶液中沥青质聚集的初始阶段:粘度和NMR弛豫研究

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In crude oil-toluene solutions dynamic viscosity η and spin-spin relaxation time T_2 were measured as functions of asphaltene concentration C in the range of 10-300 mg/1. The results were supplemented by studies of optical absorption. Extrema in the measured concentration dependencies are attributed to a transient predominance of specific asphaltene aggregates―from dimers to stacked molecular nanoclusters (MNCs) of four monomers. The strikingly non-ideal properties of solutions with C below 150-170 mg/l are attributed to the strong interactions between asphaltene species. At higher C the solution properties are evidently determined by the weaker interacting MNCs and the concentration effects are closer to those in ideal fluid mixtures. The observed re-entrant η(T_2) behaviour in asphaltene solutions hypothetically has the same origin as in supercooled or demixing molecular systems, where anomalous structural and dynamical features are often explained by emerging heterogeneity due to transient spontaneous clustering.
机译:在原油-甲苯溶液中,动态粘度η和自旋旋转弛豫时间T_2作为沥青质浓度C的函数进行测量,范围为10-300 mg / 1。通过光吸收研究补充了结果。所测得的浓度依赖性极高归因于特定沥青质聚集体的短暂占主导地位-从二聚体到四种单体的堆叠分子纳米簇(MNC)。 C含量低于150-170 mg / l的溶液的非理想特性归因于沥青质物质之间的强相互作用。在较高的温度下,溶液性质显然是由较弱的相互作用的跨国公司决定的,而且浓度效应更接近于理想流体混合物中的浓度效应。假设在沥青质溶液中观察到的折返η(T_2)行为与过冷或混合分子系统的起源相同,在该系统中,异常结构和动力学特征通常由瞬态自发聚集引起的异质性解释。

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