He Weidong, Ge Jijiang, Zhang Guicai, Jiang Ping, Jin Luchao
College of Petroleum Engineering and State Key Laboratory of Heavy Oil Process, China University of Petroleum, Qingdao, Shandong 266580, P. R. China.
SINOPEC Research Institute of Safety Engineering, Qingdao, Shandong 266100, P. R. China.
ACS Omega. 2019 Jul 22;4(7):12410-12417. doi: 10.1021/acsomega.9b00495. eCollection 2019 Jul 31.
Extended surfactants with the oxypropylene (PO) group and ethoxylated anionic surfactants with the oxyethylene (EO) group have a high salt tolerance capability. Most of the researches on extended surfactants and ethoxylated anionic surfactants focused on the microemulsion, solubilization, and interfacial tension (IFT) of concentrated surfactant solutions, whereas a few researches focused on the IFT of dilute surfactant solutions. Moreover, a previous work focused only on surfactants with PO numbers greater than 4 and copolymers of PO and EO. The effects of extended surfactants containing short PO chains and no EO groups have not been examined. We measured the IFT and optimal salinity between -alkanes and dilute solutions of extended surfactants or ethoxylated sulfonates at 30 °C. The effects of the surfactant structure on the equilibrium interfacial tension (IFT) and optimal salinity of the system were studied in detail. As for the effects on IFT, results indicate that the introduction of PO groups leads to their enhanced capability to reduce the IFT prior to cross-salinity and a reduction in the IFT between -alkanes and surfactant solutions to ultralow values (smaller than 0.01 mN/m) near the optimal salinity. It was also found that extended surfactants with different alkyl chains also entail a cross-salinity; at values lower than the cross-salinity, the IFT reduction capacity of extended surfactants with a long alkyl chain (C16P3SO3) is better than that of extended surfactants with a short alkyl chain (C13P3SO3). As for the effect on the optimal salinity, it was found that the optimal salinity of extended surfactants is lower than that of ethoxylated sulfonates for the same oil phase. It was also found that the optimal salinity of extended surfactants first increased and later decreased with increasing PON. This finding is first proposed based on summarizing some researchers' studies and our experiments.
带有氧化丙烯（PO）基团的扩展表面活性剂以及带有氧化乙烯（EO）基团的乙氧基化阴离子表面活性剂具有较高的耐盐能力。大多数关于扩展表面活性剂和乙氧基化阴离子表面活性剂的研究集中在浓缩表面活性剂溶液的微乳液、增溶作用和界面张力（IFT）上，而少数研究关注稀表面活性剂溶液的IFT。此外，先前的工作仅关注PO数大于4的表面活性剂以及PO和EO的共聚物。含短PO链且无EO基团的扩展表面活性剂的影响尚未得到研究。我们在30℃下测量了正构烷烃与扩展表面活性剂或乙氧基化磺酸盐稀溶液之间的IFT和最佳盐度。详细研究了表面活性剂结构对体系平衡界面张力（IFT）和最佳盐度的影响。至于对IFT的影响，结果表明，PO基团的引入导致它们在交叉盐度之前降低IFT的能力增强，并且在最佳盐度附近，正构烷烃与表面活性剂溶液之间的IFT降低至超低值（小于0.01 mN/m）。还发现具有不同烷基链的扩展表面活性剂也存在交叉盐度；在低于交叉盐度的值时，长烷基链扩展表面活性剂（C16P3SO3）降低IFT的能力优于短烷基链扩展表面活性剂（C13P3SO3）。至于对最佳盐度的影响，发现对于相同的油相，扩展表面活性剂的最佳盐度低于乙氧基化磺酸盐的最佳盐度。还发现扩展表面活性剂的最佳盐度随着PON的增加先升高后降低。这一发现是在总结一些研究人员的研究和我们的实验的基础上首次提出的。
