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摘要: 采用量子化学AM1方法对石油胶质进行了优化计算，得到石油胶质单层结构SG、双层结构DG和三层结构TG的优化构型和分子间作用能。结果表明，石油胶质的稠环芳烃和脂环部分大体为平面结构，支链部分也伸展在平面上。分子中稠环、脂环和侧链中的C—C键长均分别比单独苯环、脂肪环和烷烃的C—C键短。侧链中的C—C键比芳环和脂环的C—C键弱，在催化剂的作用下将优先裂解。重叠形成DG和TG后，键长、键角和电荷略有变化。胶质分子的极性基团间存在氢键作用，DG和TG分子间的作用能分别为－22.8416kJ/mol和－43.8455kJ/mol。双层胶质DG和三层胶质TG结构的体积较大，难以扩散到分子筛催化剂的孔道内。Abstract: Quantum chemical calculations have been performed on the structure of petroleum gums. The structures of the single layer (SG), double layers (DG) and triple layers (TG) for the petroleum gums were obtained. The parts of aromatic rings and alicyclic rings are approximate plane structures, while alkyl side chains extend from the plane. The distances of C—C bonds in aromatic rings, alicyclic rings and alkyl side chains of the gum are all shorter than those in benzene ring, naphthenes and alkyl group. The bonds in alkyl side chains are weaker than those in aromatic rings and alicyclic rings. This suggests that the bonds in alkyl side chains can be broken easily with proper catalysts. DG and TG are slightly different in bond distances, bond angles and net charges. Moreover, hydrogen bonds (H-bonds) are found between layers. The action energies in DG and TG are -22.8416kJ/mol and -43.8455kJ/mol, respectively. The large bulks of DG and TG may cause obstructs for their diffusion into the holes of molecular sieves.
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Key words:
- petroleum gums /
- structure properties /
- quantum chemistry
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