Abstract: In this paper, the adsorption behavior of polyoctadecyl acrylate (POA) in model crude oil on the surface of nano⁃SiO2 particles modified by methyl was investigated by performing molecular dynamics (MD) simulations. The adsorption model of model crude oil including POA molecule on the surface of nano⁃SiO₂ particles was constructed. The model crude oil consists of asphaltene, resin, aromatic hydrocarbons and alkanes. The surface of nano⁃SiO₂ particles was modified with three different degree of methyl. Several parameters such as the adsorption energy, relative density distribution, the mean square displacement and radial distribution function were analyzed. The results show that the unmodified surface is firstly adsorbed by asphaltene of strong polarity while the surface of 100% methyl⁃modified is firstly adsorbed by n⁃alkanes. The surface of 50% methyl⁃modified particles is firstly adsorbed by aromatic hydrocarbons. The results also indicate that the surface of 50% methyl⁃modified particles is not only more conducive to the stable adsorption of POA molecules, but also conducive to POA molecules to form a better adsorption configuration. What’ more, on the surface of 50% methyl⁃modified particles, the interaction between POA molecule and C₂₄H₅₀ molecules is stronger, and the distribution of C₂₄H₅₀ molecules is more aggregated. Finally, the study of this paper provides a method for studying the mechanism of pour point depressants composed of polymer and inorganic nanoparticle and provides theoretical guidance for the experimental modification of nanometer particles in nano⁃hybrid pour point depressant.

Key words: POA, Adsorption, Methy modification, Nano?SiO₂ particle, Molecular dynamics simulation

摘要： 采用分子动力学方法（MD）研究模拟含蜡原油环境中聚丙烯酸十八酯（POA）分子在甲基改性纳米SiO2颗粒表面的吸附行为，构建了包含POA分子的模拟含蜡原油体系在三种不同甲基改性程度的纳米SiO2颗粒表面的吸附模型，分析了吸附能、密度分布、均方位移、径向分布函数等参量。结果表明，未改性的颗粒表面最先吸附沥青质等极性较强的物质；100%甲基改性的颗粒表面最先吸附烷烃；50%甲基改性的颗粒表面最先吸附芳香烃、POA，且50%甲基改性表面更有利于POA分子的稳定吸附，有利于POA分子形成侧链伸展更好的吸附构型。研究也发现，在50%甲基改性的颗粒表面，POA分子与蜡分子（C24H50）之间的相互作用最强，C24H50分子的分布最聚集。此研究为纳米杂化降凝剂中纳米颗粒的有机实验改性提供了理论指导，为聚合物/纳米颗粒降凝剂的作用机理研究提供了方法。

关键词: POA, 吸附, 甲基改性, 纳米SiO2颗粒, 分子动力学模拟