兖州煤大分子结构模型构建及其分子模拟

摘要

结合兖州煤的工业分析与元素分析及13C CP/MAS NMR实验结果构建了其大分子结构模型；芳香化合物以苯为主；脂肪结构以脂肪侧链、环烷烃和氢化芳环的形式存在,且甲基、亚甲基和次甲基的含量相当；17个氧原子分别以羧基、羰基与羟基型式存在；三个氮原子分别以吡啶与吡咯的形式存在；五个硫原子以噻吩型硫的型式存在.采用分子力学(MM)和分子动力学(MD)对兖州原煤化学结构模型进行能量最小化模拟,显示稳定大分子结构的主要能量按大小排序依次为范德华能、键扭转能、键角能与键伸缩能；分子内芳香层片之间的π-π相互作用,使其以近似平行的方式排列.量子化学半经验方法(AM1)模拟结果表明,羰基碳原子相连的C-C键的活性比较高；模型中与S相连的C原子、边缘C原子都有较多的负电荷,易于发生氧化反应,而芳香碳原子所带电荷较少,稳定性很高.%Based on proximate and ultimate analysis, 13C CP/MAS NMR data of Yanzhou coal, a macromolecular structural model was constructed. In this model, benzene is the main aromatic compound and aliphatic structure exists mainly in the forms of aliphatic side chains, cycloalkanes and hydrogenated aromatic rings. The methyl proportion is similar to the total proportion of methylene and methine groups. Seventeen O atoms are present as carboxyl, carbonyl and hydroxyl groups and three N atoms exist in the forms of pyridine and pyrrole, while five S atoms in the form of thiophenic S. Molecular mechanics (MM) and molecular dynamics (MD) techniques were used to carry out energy minimization simulations on this model. The simulation results indicate that stabilization of the macromolecular structure is due to the energies of van der Waals, torsion, angle, bond and inversion in descending order of importance, and intramolecular it-it interactions between aromatic layers enables their quasi-parallel arrangement. Semi-empirical quantum chemistry (AMI) simulation indicates that the C-C bonds adjacent to carbonyl C atoms exhibit higher activity, and C atoms adjacent to S atoms and terminal C atoms are more negatively charged, which therefore prone to undergo oxidation reactions, while aromatic C atoms are characterized by fewer charges and very high stability.