Lange Bregado Jurgen, Secchi Argimiro R, Nele Marcio
Chemical Engineering Program, COPPE, Universidade Federal do Rio de Janeiro, Cidade Universitária, Rio de Janeiro, CP 21941-914, Brazil.
Chemical and Biochemical Process Engineering Program, Escola de Química, Universidade Federal do Rio de Janeiro, Cidade Universitária, Rio de Janeiro, CP 21941-909, Brazil.
Langmuir. 2025 Sep 16;41(36):24593-24618. doi: 10.1021/acs.langmuir.5c02957. Epub 2025 Sep 2.
During the extraction of crude oil, water-in-oil (W/O) emulsions are mostly formed at a high pH, where water droplets can be stabilized by anionic asphaltene molecules on the surface. The study of driving forces in the electro-coalescence of these emulsions is fundamental to the efficient design of the oil dehydration process. We studied by molecular dynamics the electro-coalescence of two asphaltene-laden droplets suspended in -hexane as a model oil. The findings indicate that a low number of anionic asphaltenes per water droplet and a moderate electric field strength () allow optimal droplet-droplet coalescence conditions to be reached, which is favored by high electrical polarization of water droplets. Under these conditions, it has been found that the diffusion and polarity of water molecules are enhanced, favoring the formation of the liquid bridge between colliding droplets and reducing the droplet-droplet coalescence time. On the contrary, with a high number of asphaltenes per droplet and , the droplet-droplet coalescence is hindered and/or retarded due to the steric effect of asphaltene aggregation at the interface between water droplets. Here, the high ionic conductivity (σ) of water droplets and low interfacial tension (γ) before the formation of the liquid bridge led to the formation of a water chain (WC) between electrodes, an undesirable phenomenon impairing the dehydration efficiency in the coalescer. This study demonstrates that W/O emulsions with anionic asphaltenes under conditions of relatively low σ and somewhat high γ at moderate (around the critical ) promote complete droplet-droplet coalescence and prevent WC formation.
在原油开采过程中，油包水（W/O）乳液大多在高pH值下形成，此时水滴可通过表面的阴离子沥青质分子得以稳定。研究这些乳液电聚结过程中的驱动力对于高效设计原油脱水工艺至关重要。我们通过分子动力学研究了悬浮于正己烷（作为模拟油）中的两个含沥青质液滴的电聚结过程。研究结果表明，每个水滴中阴离子沥青质数量较少且电场强度适中时，可达到最佳的液滴 - 液滴聚结条件，水滴的高电极化有利于此条件的达成。在这些条件下，发现水分子的扩散和极性增强，有利于在碰撞液滴之间形成液桥并缩短液滴 - 液滴聚结时间。相反，当每个液滴中沥青质数量较多且电场强度较高时，由于沥青质在水滴界面处聚集的空间位阻效应，液滴 - 液滴聚结受到阻碍和/或延迟。在此情况下，在液桥形成之前水滴的高离子电导率（σ）和低界面张力（γ）导致电极之间形成水链（WC），这是一种会降低聚结器脱水效率的不良现象。本研究表明，在中等电场强度（约临界值）下，具有相对较低σ和略高γ条件的含阴离子沥青质的W/O乳液可促进完全的液滴 - 液滴聚结并防止水链形成。
