Department of Chemical Engineering , University of California , Santa Barbara , California 93106 , United States.
Laboratory for Analysis and Architecture of Systems , 31031 Toulouse , France.
Langmuir. 2018 May 15;34(19):5409-5415. doi: 10.1021/acs.langmuir.8b00176. Epub 2018 May 1.
Surface-active asphaltene molecules are naturally found in crude oil, causing serious problems in the petroleum industry by stabilizing emulsion drops, thus hindering the separation of water and oil. Asphaltenes can adsorb at water-oil interfaces to form viscoelastic interfacial films that retard or prevent coalescence. Here, we measure the evolving interfacial shear rheology of water-oil interfaces as asphaltenes adsorb. Generally, interfaces stiffen with time, and the response crosses over from viscous-dominated to elastic-dominated. However, significant variations in the stiffness evolution are observed in putatively identical experiments. Direct visualization of the interfacial strain field reveals significant heterogeneities within each evolving film, which appear to be an inherent feature of the asphaltene interfaces. Our results reveal the adsorption process and aged interfacial structure to be more complex than that previously described. The complexities likely impact the coalescence of asphaltene-stabilized droplets, and suggest new challenges in destabilizing crude oil emulsions.
表面活性沥青质分子在原油中天然存在，通过稳定乳状液滴，在石油工业中造成严重问题，从而阻碍水和油的分离。沥青质可以在油水界面吸附，形成粘弹性界面膜，阻碍或防止聚结。在这里，我们测量了沥青质吸附时油水界面的演化界面剪切流变学。通常，界面随时间变硬，响应从粘性主导转变为弹性主导。然而，在假定相同的实验中观察到界面刚度演化的显著变化。界面应变场的直接可视化显示，每个演化膜内都存在显著的非均质性，这似乎是沥青质界面的固有特征。我们的结果表明，吸附过程和老化的界面结构比以前描述的更为复杂。这些复杂性可能会影响沥青质稳定液滴的聚结，并在使原油乳状液不稳定方面带来新的挑战。
