Problematic Stabilizing Films in Petroleum Emulsions: Shear Rheological Response of Viscoelastic Asphaltene Films and the Effect on Drop Coalescence

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• 作者：David Harbottle ; Qian Chen ; Krishna Moorthy ; Louxiang Wang ; Shengming Xu ; Qingxia Liu ; Johan Sjoblom ; Zhenghe Xu
• 刊名：Langmuir
• 出版年：2014
• 出版时间：June 17, 2014
• 年：2014
• 卷：30
• 期：23
• 页码：6730-6738
• 全文大小：437K
• 年卷期：v.30,no.23(June 17, 2014)
• ISSN：1520-5827

文摘

Adsorption of asphaltenes at the water鈥搊il interface contributes to the stability of petroleum emulsions by forming a networked film that can hinder drop鈥揹rop coalescence. The interfacial microstructure can either be liquid-like or solid-like, depending on (i) initial bulk concentration of asphaltenes, (ii) interfacial aging time, and (iii) solvent aromaticity. Two techniques鈥攊nterfacial shear rheology and integrated thin film drainage apparatus鈥攑rovided equivalent interface aging conditions, enabling direct correlation of the interfacial rheology and droplet stability. The shear rheological properties of the asphaltene film were found to be critical to the stability of contacting drops. With a viscous dominant interfacial microstructure, the coalescence time for two drops in intimate contact was rapid, on the order of seconds. However, as the elastic contribution develops and the film microstructure begins to be dominated by elasticity, the two drops in contact do not coalescence. Such step-change transition in coalescence is thought to be related to the high shear yield stress (10⁴ Pa), which is a function of the film shear yield point and the film thickness (as measured by quartz crystal microbalance), and the increased elastic stiffness of the film that prevents mobility and rupture of the asphaltene film, which when in a solid-like state provides an energy barrier against drop coalescence.