Adsorption kinetics of asphaltenes at oil/water interface: Effects of concentration and temperature. (15th January 2018)

• Record Type: Journal Article
• Authors: Zhang, Shuo; Zhang, Ling; Lu, Xi; Shi, Chen; Tang, Tian; Wang, Xiaogang; Huang, Qingxue; Zeng, Hongbo
• Is Part Of: Fuel. Volume 212(2018)
• Page Start: 387
• Page End: 394
• Publication Date: 2018-01-15
• Subjects: IFT interfacial tension -- CNAC critical nanoaggregation concentration -- CCC critical clustering concentration; Asphaltenes -- Adsorption kinetics -- Dynamic interfacial tension -- Concentration -- Temperature; Fuel -- Periodicals; Coal -- Periodicals; Coal; Fuel; Periodicals; 662.6
• DOI: 10.1016/j.fuel.2017.10.051
• Languages: English
• ISSNs: 0016-2361

Abstract

Graphical abstract: Highlights: Asphaltene concentration and temperature affect adsorption kinetics of asphaltenes. The adsorption kinetics of asphaltenes to oil/water interface includes three regimes. Asphaltene concentration & temperature affect the interfacial diffusion coefficient. Maximum surface access concentration of asphaltenes depends on temperature. Abstract: Asphaltenes are the heaviest components in crude oil. It is generally believed that asphaltenes adsorbed at oil/water interface can form a protective layer to stabilize the water-in-oil or oil-in-water emulsions. In this work, the effects of asphaltene concentration and temperature on the dynamic interfacial tension (IFT) of oil (i.e., toluene)/water interface were systematically investigated using a pendent drop shape method. The adsorption process shows three stages as a function of adsorption time. In Regime I, the reduction kinetics of IFT is diffusion-controlled, during which asphaltenes are adsorbed to the oil/water interface spontaneously. The interfacial diffusion coefficient of asphaltenes to the oil/water interface was found to increase with increasing temperature and decreasing asphaltene concentration, which is much lower than the bulk diffusion coefficient predicated by the Stokes–Einstein equation. In Regime II, the steric hindrance arisen from the adsorbed asphaltenes at oil/water interface from Regime I tends to inhibit further adsorption of asphaltenes to the interface. In Regime III, continuous adsorption of asphaltenes to the sublayer of the interface and reconfiguration of adsorbed asphaltenes or asphaltene aggregates occur, contributing to the continuous but very slow reduction of dynamic interfacial tension. Our results provide useful insights into the adsorption kinetics and adsorption mechanism of asphaltenes at oil/water interfaces under different asphaltene concentration and temperature conditions, with implications to many related interfacial phenomena (e.g., emulsion stability) where asphaltenes are present in oil production.