沥青质及其亚组分与烷基苯磺酸盐溶液在降低界面张力中的协同作用

利用混合溶剂沉淀法将原油中的沥青质分为4个亚组分, 研究了含有各组分的模拟油与烷基苯磺酸钠(p-S14-4, p为对二甲苯; 14表示烷基链上有14个碳原子; S表示表面活性剂; 4表示芳基在长链烷基的4号碳原子上)水溶液间的动态界面张力(DIFTs). 结果表明, 沥青质及其亚组分的分子尺寸、 浓度和极性对DIFTs有显著影响. 分子尺寸较大的沥青质亚组分与p-S14-4分子之间难以形成混合吸附膜, 协同作用较弱, DIFTs曲线呈“L”形, 最小界面张力(IFT_min)受浓度和极性的影响较小. 在高浓度时, 分子尺寸较小的沥青质及其亚组分快速扩散至界面与p-S14-4分子形成紧密的混合吸附膜, 能够快速降低界面张力(IFT); 随着时间的延长, 界面层的分子发生重排, 导致DIFTs曲线呈“V”形, 且在这种情况下沥青质及其亚组分的极性越高, 降低IFT的协同作用越明显, IFT_min越低.

Synergism Between Asphaltene and Its Subfractions and Alkylbenzene Sulfonate Solutions in Lowering Dynamic Interfacial Tensions†

Asphaltene extracted from Daqing crude oil was separated into four subfractions by precipitation method of mixed solvents. The dynamic interfacial tensions(DIFTs) of alkylbenzene sulfonate(p-S14-4) aqueous solutions against model oil containing asphaltene and its subfractions were measured. The results revealed that the molecular size, concentration and polarity of asphaltene and its subfractions had a significant effect on DIFTs. For asphaltene subfractions with larger molecular size, DIFTs curves presented the "L" shape and minimum interfacial tension(IFT_min) had a slight variation with the concentration and polarity, because the formation of mixed adsorption films between them and p-S14-4 molecules was difficult. For asphaltene and its subfractions with smaller molecular size, at high concentrations, these subfractions quickly diffused to the interface to form a tightly mixed adsorption film with p-S14-4 molecules, which can instantly lower the interfacial tension(IFT); with time going on, the molecules at the interface layer rearranged. As a result, the DIFTs curves presented "V" shape. Moreover, in this case, asphaltene and its subfractions with higher polarity resulted in lower IFT_min because of the more obvious synergism.