基于分子动力学方法研究化学驱表面活性剂降低油/水界面张力机制

For chemical flooding processes, hot issues and problems are concentrated on how to synthesis and develop highly efficient and low-cost surfactants. However there were no researches on the relationships between the structures and properties at the point of the molecular level. Molecular dynamics methods can be used to elucidate the self-assembly behavior of surfactants at the point of molecular level, while the behavior cannot be gotten from the experiments. Series of alkylaryl sulfonate will be used in this project, mainly due to their highly efficient interfacial properties and lower costs. Being based on the Computational Chemistry and Interfacial Molecular Engineering Theory, molecular dynamics simulation methods will be used, the simulation results can clarify the mechanism of reducing the oil/water interfacial tension, the relationship between the molecular structure and interfacial properties can get. Our researches will provide some basic theories for the designation, selection and application of chemical flooding surfactants. .Our researches mainly focus on the followings: (1) Relationship between the surfactant molecular structure, solution composition and the interfacial self-assembly behavior are being investigated systematically; (2) Microscopic mechanism of surfactants will be described on how to reduce the oil/water interfacial tension at the point of the molecular level; (3) According to the principles of Molecular Biology, quantitative QSAR Model are being designed and built being combined with the property controlled parameters, the interfacial characterizations, the analytical results and mechanism analysis. The model can describe the oil/water interfacial properties for chemical flooding surfactants. Our achievements can not only provide the theoretical basis on the principle of reducing the oil/water interfacial tension for chemical flooding surfactants at the point of molecular level, but also enrich the fundamental theories of colloid and interfacial chemistry and chemical flooding. Therefore it has great significance on scientific research.

高效、低成本表面活性剂研制和开发一直是化学驱领域研究的热点和难题，尚无在分子水平对其构效关系的系统研究。分子动力学方法可实现分子水平阐明表面活性剂界面自组装行为，达到实验难以实现的条件。本项目以性能较好、应用成熟的烷基芳基磺酸盐为研究对象，基于计算化学和界面分子工程学，采用分子动力学模拟方法，研究表面活性剂降低油水界面张力机制，建立分子结构与界面性能间定量化构效关系，为化学驱表面活性剂设计、筛选和应用，提供理论依据。.具体包括:(1)系统研究表面活性剂分子结构和溶液环境变化与界面自组装行为间的相互关系；(2)分子水平描述表面活性剂降低油/水界面张力微观机制；(3)应用分子生物学原理，综合性能调控参数、表征分析与机理研究，构筑描述化学驱表面活性剂油/水界面性能“定量化构效关系模型”。其科学意义在于从分子层面阐明化学驱表面活性剂降低油/水界面张力机制，丰富和完善胶体与界面化学和化学驱基础理论。

本项目采用分子动力学模拟方法，以系列烷基芳基磺酸盐为研究对象，对化学驱表面活性剂降低油/水界面张力机制开展基础理论研究，通过研究取得如下认识：.1.利用量子化学优化软件Gamess对系列烷基苯、甲苯和二甲苯等烷基芳基磺酸盐结构进行优化，采用在线拓扑生成网站对烷基芳基磺酸盐结构进行拆分合并，获得联合原子拓扑文件，水分子选用SPC/E模型。使用分子堆积软件Packmol构建模拟体系，应用Gromacs2018对模拟体系运用最速下降法和共轭梯度法进行能量最小化；使用正则系综进行200 ps模拟，使用Velocity Rescaling和Berendsen进行1.0 ns等温等压模拟，使用Nose-Hoover和Parrinello-Rahman进行20 ns等温等压模拟，提取最后2.0 ns数据。.2.获得烷基芳基磺酸盐在油/水界面自组装行为的动力学信息，表明烷基芳基磺酸盐在油/水界面呈不规则单层膜分布，烷基芳基磺酸盐可降低油水界面总能量，采用序参数考察疏水烷基链与油相分子和水分子间相互作用，芳环中取代基增加降低苯环电荷密度，芳环为甲苯和二甲苯结构烷基链夹角和溶剂可及面积较为接近。.3.通过考察油相与烷基芳基磺酸盐分子间的径向分布函数和疏水烷基碳链序参数，获得烷基芳基磺酸盐对油相分子亲和能力，通过判断疏水烷基链的有序性确定与油相分子之间的匹配关系。.4.获得不同溶液环境系列烷基芳基磺酸盐油/水界面分子动力学信息，表明烷基芳基磺酸盐分子中SO3-中氧原子与Ca2+的作用强度高于与Na+作用强度，Ca2+对烷基芳基磺酸盐分子中SO3-之间静电作用较强；Na2CO3加入会与磺酸基上氧原子争夺钠离子，钠离子优先与CO32-离子作用，磺酸基氧原子作用数量减少；异丙醇对磺酸基中硫原子与钠离子有促进作用，磺酸基与水分子之间相互作用有所减弱。.5.精细合成系列烷基芳基磺酸盐表面活性剂，采用红外光谱、核磁共振氢谱和碳谱等对中间体和目标产物结构进行表征，运用旋滴界面张力仪测定不同油相下界面张力；结合测定油水界面张力值，构建油相描述符、结构描述符、静电描述符和能量描述符与界面张力之间定量构效关系，为设计和筛选化学驱表面活性剂提供理论基础。