Tchoukov Plamen, Yang Fan, Xu Zhenghe, Dabros Tadeusz, Czarnecki Jan, Sjöblom Johan
Department of Chemical and Materials Engineering, University of Alberta , Edmonton, Alberta, Canada.
Langmuir. 2014 Mar 25;30(11):3024-33. doi: 10.1021/la404825g. Epub 2014 Mar 11.
Drainage kinetics, thickness, and stability of water-in-oil thin liquid emulsion films obtained from asphaltenes, heavy oil (bitumen), and deasphalted heavy oil (maltenes) diluted in toluene are studied. The results show that asphaltenes stabilize thin organic liquid films at much lower concentrations than maltenes and bitumen. The drainage of thin organic liquid films containing asphaltenes is significantly slower than the drainage of the films containing maltenes and bitumen. The films stabilized by asphaltenes are much thicker (40-90 nm) than those stabilized by maltenes (∼10 nm). Such significant variation in the film properties points to different stabilization mechanisms of thin organic liquid films. Apparent aging effects, including gradual increase of film thickness, rigidity of oil/water interface, and formation of submicrometer size aggregates, were observed for thin organic liquid films containing asphaltenes. No aging effects were observed for films containing maltenes and bitumen in toluene. The increasing stability and lower drainage dynamics of asphaltene-containing thin liquid films are attributed to specific ability of asphaltenes to self-assemble and form 3D network in the film. The characteristic length of stable films is well beyond the size of single asphaltene molecules, nanoaggregates, or even clusters of nanoaggregates reported in the literature. Buildup of such 3D structure modifies the rheological properties of the liquid film to be non-Newtonian with yield stress (gel like). Formation of such network structure appears to be responsible for the slower drainage of thin asphaltenes in toluene liquid films. The yield stress of liquid film as small as ∼10(-2) Pa is sufficient to stop the drainage before the film reaches the critical thickness at which film rupture occurs.
研究了由在甲苯中稀释的沥青质、重油（沥青）和脱沥青重油（软沥青质）获得的油包水型稀乳液薄膜的排水动力学、厚度和稳定性。结果表明，沥青质在比软沥青质和沥青低得多的浓度下就能稳定有机液体薄膜。含沥青质的有机液体薄膜的排水速度明显慢于含软沥青质和沥青的薄膜。由沥青质稳定的薄膜（40 - 90纳米）比由软沥青质稳定的薄膜（约10纳米）厚得多。薄膜性质的这种显著差异表明有机液体薄膜的稳定机制不同。对于含沥青质的有机液体薄膜，观察到明显的老化效应，包括薄膜厚度逐渐增加、油/水界面刚性以及亚微米尺寸聚集体的形成。在甲苯中含软沥青质和沥青的薄膜未观察到老化效应。含沥青质的稀液体薄膜稳定性增加和排水动力学降低归因于沥青质在薄膜中自组装并形成三维网络的特定能力。稳定薄膜的特征长度远超过文献报道的单个沥青质分子、纳米聚集体甚至纳米聚集体簇的尺寸。这种三维结构的形成改变了液膜的流变性质，使其具有屈服应力（类凝胶）的非牛顿性质。液膜小至约10^(-2) 帕的屈服应力足以在薄膜达到发生破裂的临界厚度之前阻止排水。
