Ahmadi Mohammad, Hassanzadeh Hassan, Abedi Jalal
Department of Chemical and Petroleum Engineering, Schulich School of Engineering, University of Calgary, 2500 University Drive NW, Calgary, AB T2N 1N4, Canada.
Phys Chem Chem Phys. 2020 Sep 23;22(36):20758-20770. doi: 10.1039/d0cp03026k.
A significant amount of research work has been conducted to shed light on the asphaltene aggregation behavior under no-flow conditions. However, their aggregation under shear flow conditions is poorly understood mainly due to the lack of research studies performed on this subject. In this work, we employ the Brownian dynamics simulation to examine the shear flow effects on the self-assembly behavior of asphaltenes. Three volume fractions φ of asphaltene nanoaggregates, ranging from 1 to 7%, are used to investigate the asphaltene aggregation behavior in heptane and heptol (i.e., a solvent containing both heptane and toluene) solvents under shear rates of [small gamma, Greek, dot above] = 0.0-2.5 × 108 s-1. The shear is applied parallel to the x-axis and the shear-gradient is along the y-axis. Under shear flow conditions, the formation of the percolating networks of aggregates is triggered at φ = 3% which is lower than that under the no-flow conditions, i.e., φ = 7%. In both solvent systems, the formed networks mainly percolate along the x- or z-axis to experience less shear-gradient. At all volume fractions, an increase in the shear rate from [small gamma, Greek, dot above] = 0.0 to [small gamma, Greek, dot above] = 2.5 × 108 s-1 resulted in two to three orders of magnitude improvement in the self-diffusion coefficients of colloids.
为了阐明无流动条件下沥青质的聚集行为，已经开展了大量的研究工作。然而，由于缺乏关于该主题的研究，人们对其在剪切流动条件下的聚集情况了解甚少。在这项工作中，我们采用布朗动力学模拟来研究剪切流动对沥青质自组装行为的影响。使用三种体积分数φ（范围为1%至7%）的沥青质纳米聚集体，来研究在[小γ，希腊字母，上方有点] = 0.0 - 2.5×10⁸ s⁻¹的剪切速率下，庚烷和庚醇（即一种同时含有庚烷和甲苯的溶剂）溶剂中沥青质的聚集行为。剪切力沿x轴方向施加，剪切梯度沿y轴方向。在剪切流动条件下，聚集体渗流网络的形成在φ = 3%时被触发，这低于无流动条件下的φ = 7%。在两种溶剂体系中，形成的网络主要沿x轴或z轴渗流，以减少剪切梯度。在所有体积分数下，剪切速率从[小γ，希腊字母，上方有点] = 0.0增加到[小γ，希腊字母，上方有点] = 2.5×10⁸ s⁻¹，导致胶体的自扩散系数提高了两到三个数量级。
