沥青质分子聚集体的聚集内因

Aggregation Mechanism of Asphaltene Molecular Aggregates

运用量子力学、分子动力学等方法,研究沥青质分子聚集体形成过程的分子构型变化、能量变化以及电子分布情况。结果表明:沥青质分子形成聚集体过程中形变能很小,沥青质分子发生形变不是沥青质聚集体形成的决定因素,但为沥青质分子聚集进而形成聚集体提供基础,沥青质分子具有很强的本征聚集活性;沥青质分子间相互作用能很大,是沥青质分子聚集体形成的决定因素,其中,属于分子间固有属性的范德华力及泡利排斥作用之和相对较小,与沥青质分子结构特征相关的π-π相互作用及氢键作用之和很大,表明由沥青质分子的大芳环体系和多杂原子的结构特征引起的π-π相互作用及氢键作用是导致形成沥青质分子聚集体的主要原因;在所研究体系中,金属卟啉分子与含吡啶氮的沥青质分子通过π-π相互作用而非轴向配位作用形成聚集体。

Quantum mechanics and molecular dynamics were employed to study changes of molecular configurations,energies and electron populations in the formation of asphaltene molecular aggregates.The results show that deformation energies of asphaltene molecules are quite low during aggregation processes,indicating their deformation behavior is not the decisive factor for aggregations.Asphaltene molecules have strong intrinsic aggregation activities due to their structural features which causes intensive intermolecular interactions.Among intermolecular forces,the sum ofπ-πinteractions and hydrogen bonds is greater than that of Van der Waals interactions and Pauli exclusions,indicating that the main driving forces for the formation of asphaltene aggregates areπ-πinteractions and hydrogen bonds,which derived from the specific structures of macroaromatic ring systems and multiple heteroatoms in asphaltene molecules.In addition,metal porphyrin and pyridine-nitrogen-containing asphaltene molecules form aggregates throughπ-πinteractions rather than axial coordination interactions.