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化学学报
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化学学报 ›› 2011, Vol. 69 ›› Issue (17): 2053-2062. 上一篇    下一篇

研究论文

石油化学粗粒化分子力学/分子动力学力场: I. 烷烃的粗粒化模型

张宏玉*,1，王艳艳1，陶国强1，桂彬1，殷长龙2，柴永明2，阙国和1   

  1. (1中国石油大学(华东)化工学院 重质油国家重点实验室 青岛 266555)
    (2中国石油大学(华东)化工学院 中国石油天然气集团公司催化重点实验室 青岛 266555)
  • 投稿日期:2010-09-24 修回日期:2011-04-20 发布日期:2011-05-03
  • 通讯作者: 张宏玉 E-mail:nanogroup@upc.edu.cn
  • 基金资助:

    自然科学基金;石油科技中青年创新基金;研究生创新基金

Coarse Grained Molecular Mechanics (MM)/Molecular Dynamics (MD) Force Field for Petroleum Chemistry: I. Coarse Grained Model for Alkanes in Petroleum

Zhang Hongyu*,1 Wang Yanyan1 Tao Guoqiang1 Gui Bin1 Yin Changlong2 Chai, Yongming2 Que, Guohe1   

  1. (1 State Key Laboratory of Heavy Oil, School of Chemical Engineering, China University of Petroleum (East China), Qingdao 266555)
    (2 Key Laboratory of Catalysis, China National Petroleum Corporation, School of Chemical Engineering, China University of Petroleum (East China), Qingdao 266555)
  • Received:2010-09-24 Revised:2011-04-20 Published:2011-05-03
  • Contact: Hongyu Zhang E-mail:nanogroup@upc.edu.cn

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提供了一种用以描述石油中烷烃分子的通用型粗粒化模型. 依据石油中烷烃的结构特征, 划分出从A1到A7共7种粗粒化珠子. 7种烷烃的粗粒化珠子含有3～6个碳原子, 与之相对应的既有直链烷烃, 也有支链烷烃. 这些基本结构单元以不同的组合方式可以得到石油中从C3～C40各种烷烃的粗粒化分子. 为了获得精确的力场参数, 采用密度泛函方法优化对应于单个粗粒化珠子的分子结构. 应用改进的Flory-Huggins方法计算得到各珠子之间的Lennard-Jones非键势能参数. 通过全原子分子动力学(AA-MD)模拟得到粗粒化珠子之间的成键势能参数. 以此数据为基础, 建立CUP 1.0粗粒化分子力学/分子动力学力场(CUP 1.0 CG MM/MD Force Field). 为了检验力场参数的准确性, 应用粗粒化分子动力学(CG-MD), 在恒温恒压(NPT)系综条件下计算了石油中37种从C3～C40烷烃模型化合物的密度. 模拟计算的结果与实验值之间的误差均小于1.0%, 优于采用针对水溶液中生物分子的MARTINI力场的计算结果. 此外, 还模拟了非键相互作用差异最大的两种粗粒化珠子所对应的丙烷和新己烷分子的相溶性, 结果表明这两种粗粒化珠子能够很好地互溶, 进一步验证了CUP 1.0力场的合理性.

关键词: 粗粒化力场, 分子动力学, 石油, 烷烃, 密度

The general coarse grained (CG) model for alkanes in petroleum was described in this paper. According to the structural characteristic of alkanes in petroleum, seven coarse grained beads were mapped from A1 to A7. Almost all of alkane molecules in petroleum can be coarse-grained by the combination of these seven beads which contain 3 to 6 carbon atoms. The seven coarse grained building blocks individually correspond to normal alkanes and isoparaffins. In order to obtain precise force field parameters, density functional theory (DFT) was employed to optimize the molecular structure corresponding to the single coarse grained bead. The non-bonded Lennard-Jones potential parameters were calculated by application of modified Flory-Huggins method. And the bonded potential parameters were obtained by all atom molecular dynamics (AA-MD) simulation. In order to test the accuracy of CUP 1.0 coarse molecular mechanism/molecular dynamics force field (CUP 1.0 CG-MM/MD) which is established on the basis of non-bonded and bonded potential parameters of seven alkane coarse grained beads, density of thirty seven model alkane compounds from C3 to C40 in petroleum was computed through coarse grained molecular dynamics (CG-MD) in NPT ensemble. The CG-MD simulation results demonstrated that none of the simulating error was beyond 1.0% than that of experimental data, which is more accurate than that calculated by MARTINI force field which is specific for biomolecules in water. In addition, the solubility between propane (A1) and neohexane (A7) was simulated by using CG molecular dynamics, which are the most distinctive in non-bond interaction strength among seven coarse grained beads. The simulating result showed that coarse grained alkane beads of A1 and A7 are completely soluble, which demonstrated the rationality of CUP 1.0 force field.

Key words: coarse grained force field, molecular dynamics, petroleum, alkanes, density