无机盐对阴离子型表面活性剂油水界面聚集行为影响的MD模拟

发布时间：2018-06-29 23:33

本文选题：无机盐 + 阴离子表面活性剂　；参考：《中国石油大学(华东)》2015年硕士论文

【摘要】：阴离子表面活性剂在三次采油中起着重要作用,其驱油原理之一是能定向吸附于油水界面,降低油水界面张力。由于阴离子表面活性剂在水溶液中解离后活性部分带负电荷,地层中的矿物离子如Na~+、Mg~(2+)和Ca~(2+)会对其界面活性产生较大影响。开展无机盐对其油水界面聚集行为影响的研究,对理解实验现象和耐盐机理有一定帮助。鉴于此,本论文采用分子动力学模拟方法,探究阴离子表面活性剂由溶液相迁移至油水界面的动力学过程,研究无机盐对该聚集过程的影响,并进一步考察无机盐对吸附在油水界面的表面活性剂界面性质的影响。由于对表面活性剂从溶液相迁移至油水界面的研究处于探索阶段,因此对该模型的合理性进行了验证。模拟结果表明,十二烷基硫酸钠(SDS)、十二烷基苯磺酸钠(SDBS)、十二烷基聚氧乙烯醚硫酸钠(AES)和十二烷基聚氧乙烯醚羧酸钠(AEC)油水界面处的界面活性由高到低的顺序为:AESAECSDBSSDS,该结果与文献中报道的实验结论一致,证明了初始模型的合理性。界面聚集过程的研究结果表明,Mg~(2+)浓度对SDBS的影响大于Na~+浓度的影响;Ca~(2+)对AES和SDBS界面活性的影响比Mg~(2+)对其界面活性的影响更大;AES耐盐性能优于SDBS。界面性质的研究结果表明,盐离子对界面处AES分子构型、界面双电层、极性头周围的水化层、盐离子与极性头相结合的倾向性等性质均有影响;理论评价无机盐对AES界面性质的影响顺序为:Ca~(2+)Mg~(2+)Na~+,该结果与文献中报道的无机盐对AES界面活性的影响规律一致;此外,当体系中Ca~(2+)浓度偏高时,Ca~(2+)与AES极性头相结合形成溶解度偏低的钙盐,进而使得AES亲水性降低,分子构型改变为整体平铺在油水界面。
[Abstract]:Anionic surfactants play an important role in tertiary oil recovery. One of the oil displacement principles is that they can be adsorbed on the oil-water interface and reduce the oil-water interfacial tension. Because the active part of anionic surfactants is negatively charged after dissociation in aqueous solution, mineral ions such as Na ~ (2), mg ~ (2) and Ca ~ (2) have a great influence on the interfacial activity of anionic surfactants. The study on the effect of inorganic salt on the aggregation behavior of oil-water interface is helpful to understand the experimental phenomenon and salt tolerance mechanism. In this paper, molecular dynamics simulation was used to study the kinetic process of the migration of anionic surfactants from solution phase to oil-water interface, and the effect of inorganic salts on the aggregation process was studied. The effect of inorganic salts on the interfacial properties of surfactants adsorbed on the oil-water interface was also investigated. The rationality of the model is verified because the study of surfactant migration from solution phase to oil-water interface is in the exploratory stage. The simulation results show that, The interfacial activity of sodium dodecyl sulfate (SDS), sodium dodecylbenzene sulfonate (SDBS), sodium dodecyl polyoxyethylene ether sulfate (AES) and sodium dodecyl polyoxyethylene ether carboxylate (AEC) at the oil-water interface is in the order of: AESAECSDBSSDSs. The experimental results reported are consistent. The rationality of the initial model is proved. The results of interfacial aggregation show that the effect of Mg2 concentration on SDBs is greater than that of Na2 concentration on the interfacial activity of AES and SDBs. The salt tolerance of AES is better than that of Mg2. The results show that salt ions have influence on the structure of AES at the interface, the double electric layer at the interface, the hydration layer around the polarity head, and the tendency of the combination of salt ion and polar head. The order of influence of inorganic salts on the interface properties of AES is: 1 Ca ~ (2) mg ~ (2) Na ~ (2) Na ~ (2), which is consistent with the law of influence of inorganic salts on the interface activity of AES. When the concentration of Ca2 in the system is on the high side, the Ca ~ (2) is combined with the polar head of AES to form calcium salt with low solubility, which leads to the decrease of the hydrophilicity of AES and the change of molecular configuration to a whole flat surface at the oil-water interface.
【学位授予单位】：中国石油大学(华东)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE357.46

【相似文献】