烃类气体对泡沫液膜稳定性影响的微观机制

Micromechanism of impact of hydrocarbon gases on stability of foam films

利用分子动力学方法构建气相层-表面活性剂/聚合物分子层-含无机盐离子的水相夹层模拟体系,微观揭示烃类气体类型对水基泡沫液膜排液特性与Ostwald熟化作用的影响机制。结果表明:相比于N2泡沫,烃类气体产生水基泡沫的液膜稳定性降低,且随着碳数增加,表面张力逐渐增大,界面形成能绝对值逐渐减小,泡沫液膜排液能力增强,第一水化层内水分子扩散系数从CH4水基泡沫体系的1.73×10^(-5)cm^(2)/s增大到C3H8水基泡沫体系的2.40×10^(-5)cm^(2)/s,相应界面水层厚度、水化层内水分子配位数则分别从10.93A和2.11减小到7.72A和1.96;由气体分子界面聚集引起的Ostwald熟化作用是影响泡沫液膜稳定性的关键;同时对于碳数高的烃类气体分子,更易渗透其所形成的泡沫液膜而诱发泡沫衰变与破裂,反映出表面活性剂分子的界面吸附构型直接影响着Ostwald熟化作用。

The sandwich simulation system of gas phase-surfactant/polymer phase-aqueous phase containing inorganic salt ions was established by the molecular dynamics method. The micromechanism of the impact of hydrocarbon gases on the film drainage and Ostwald ripening of aqueous foam was revealed. The results indicate that the film stability of foams produced by hydrocarbon gases is lower than that of N2. With the increase of carbon number of hydrocarbon gas molecules, the surface tension increases, the absolute value of interface formation energy decreases, and the film drainage capability strengthens. The diffusion coefficient of water molecules in the first hydration layer is increased from 1.73×10^(-5)cm^(2)/s in the CH4foam system to 2.40×10^(-5)cm^(2)/s in the C3H8foam system. The thickness of interfacial water layer and the coordination number of water molecules decrease from 10.93 A and 2.11 in the CH4foam system to 7.72 A and 1.96 in the C_(3)H_(8) foam system, respectively. Moreover, the Ostwald ripening activated by gas molecule aggregation at the interface is critical to the foam film’s stability. Furthermore, the hydrocarbon gas molecules with higher carbon numbers are more likely to penetrate the produced foam film and result in rupture of foams, which reflects that the adsorption configuration of surfactant molecules directly affects the Ostwald ripening.