杂原子对沥青质分子间相互作用影响的计算化学研究

 沥青中大量的沥青质分子均含杂原子，通过计算化学方法，可以分析杂原子对沥青质二聚体结构及分子间相互作用的影响，并探究其影响机理。密度泛函理论计算结果表明，杂原子的存在使分子的静电势分布差别明显。对于稠环结构相似的沥青质分子，共轭硫原子使得分子的相互作用减小，含硫沥青质较远的质心距离和硫原子相对较弱的负电势使分子的取向和质心距分布更加随机。共轭氮原子作为强负电中心，强排斥增大分子取向偏离最低能量构型的能垒，从而使沥青质二聚体的构型取向更加趋于固定。同时分子动力学结果显示，含硫沥青质对温度敏感，温度升高更严重地加剧分子排列无序；而含氮沥青质在较高温度下依旧保持相对的有序排列。

Effects of Heteroatom on Molecular Interactions of Asphaltenes: A Computational Study

A large number of asphaltene molecules in asphalt contain heteroatoms. The influence of heteroatoms on the structure and intermolecular interaction of asphaltene dimers can be analyzed by computational chemistry methods, and the influence mechanism can also be explored. Density functional theory results show a significant difference of electrostatic potential distribution in different asphaltenes caused by heteroatoms. For similar asphaltene molecules, sulfurs in condensed aromatic rings reduce intermolecular interaction, the longer centroid distance of sulfur-containing asphaltenes and the weaker negative potential of sulfur atoms make the distribution of molecular orientation and centroid distance more randomly. In contrast, as strong negative centers, conjugated nitrogen atoms increase the potential barrier which hinders the molecular orientation to deviate from the lowest energy configuration by their strong repulsion. Moreover, molecular dynamics simulations show that sulfur contained asphaltenes are more sensitive to temperature where the molecular arrangement is rapidly disordered at higher temperature, while the nitrogenous asphaltenes still maintain relatively orderly arrangement at the same temperature.