中低温煤焦油沥青质聚集体的分子间作用力

Intermolecular forces of medium/low temperature coal tar asphaltene aggregates

以中低温煤焦油沥青质为研究对象,在分析表征沥青质的结构参数与特征官能团的基础上建立沥青质模型分子,利用密度泛函理论(DFT)方法研究沥青质聚集体中分子间的π-π作用、氢键作用、酸碱作用等相互作用力。结果表明中低温煤焦油沥青质分子的芳香片结构具有较狭长且弯曲的特性,导致分子间的π-π相互作用小到可以忽略,难以形成稳定的沥青质片层聚集结构;沥青质分子间的吡咯与亚砜基、羟基与吡啶、羟基与羰基的氢键键能为21~37 kJ/mol,是形成沥青质聚集体的主要推动力,且可形成多个分子间氢键而得到具有一定空间构型的多分子聚集体;羧酸基与吡啶之间的酸碱作用能为62.86 kJ/mol,是促进形成聚集体的强作用力,但羧酸基的含量很低,形成酸碱作用的几率较低。

The asphaltenes model molecules were established according to the characterization of the structural parameters and functional groups of the asphaltenes from medium/low temperature coal tar.The density functional theory(DFT)method was adopted to determine the intermolecular forces of asphaltene aggregates,such asπ-πinteraction,hydrogen bonding and acid-base interaction.The results demonstrate that the aromatic nuclei structure of medium/low temperature coal tar asphaltene molecules is narrow and curved,resulting in theπ-πstacking interaction between molecules to be negligible.Then it is difficult to form a stack-shaped asphaltene aggregates by stacking interaction of aromatic nuclei.The bond energy of the hydrogen bonds between pyrrole and sulfoxide group,hydroxyl and pyridine,and hydroxyl and carbonyl is in the range of 21-37 kJ·mol^(-1),which are the main driving forces for the formation of asphaltene aggregates.The multi-molecular aggregate with a certain spatial configuration can be formed because of the existence of multiple intermolecular hydrogen bonds.The energy of acid-base interaction between carboxylic acid groups and pyridine is 62.86 kJ·mol^(-1),which is a strong force to promote the formation of asphaltene aggregates,but the probability of this interaction is low due to the low content of carboxylic acid groups.