石油沥青质的NMR测定及其模型分子推测

NMR determination of petroleum asphaltenes and their model molecules evaluation

从6种不同原油中分离提取了正己烷不溶的沥青质,测定了沥青质的1HNMR(NuclearMagneticResonance)和13CNMR谱,从不同类型氢和碳原子的质量分数计算得到了一系列平均结构参数,结合相对分子质量测定和元素分析,给出了沥青质基本结构单元的平均分子式,推测了模型分子的结构。结果表明,沥青质的基本结构单元可以用稠环芳烃连接环烷烃和烷基侧链并含氧、氮和硫等杂原子的单元表示,结构单元之间形成缔合体,缔合数为4～6。

~1H and^(13)C NMR spectra of 6 petroleum asphaltenes, separated from different crude oils with n-hexane as solvent, were determined with a Bruker Avance DMX500 NMR spectrometer. And then a series of average chemical structural parameters were obtained. By combining the relative molecular weight and the elemental analysis results, the average molecular formula of the asphaltene units was calculated and the model molecules were evaluated. It is found that the asphaltene units are mainly composed of polycyclic aromatics linked with naphthene rings, side aliphatic chains, and O, N and S atoms. The asphaltene units are associated each other with the association number about from 4 to 6. These results provide an efficient structural description for the further study of petroleum asphaltenes at molecular level.