Constructions of coal and char molecular models based on the molecular simulation technology
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摘要: 煤、焦是过程工业的重要原料。因此，有必要深入了解煤、焦分子结构以揭示其反应性。采用Materials Studio 7.0软件，从分子层次研究煤、焦的分子结构。根据已报道的文献，构建煤、焦的初始结构；基于分子力学原理对这些结构进行优化，使得模型物性与煤、焦物性相符；基于退火模拟算法对模型进行优化，从而使得模型密度、元素分析数据与真实值吻合；基于能量最小化原理，对煤、焦模型再次优化，从而获得其稳定、真实的分子构型。由计算结果发现，模型的估算密度、元素组成与已报道一致，说明构建的模型是有效、合理的；在模型优化过程中，相对于其他能量而言，库伦能和范德华能起着重要的作用。因此可以推断在煤、焦热加工过程中，弱键占据主要地位。另外，本文采用分子模拟技术构建煤、焦模型的方法对于构建其他复杂大分子结构有着重要的借鉴作用。Abstract: Coal and char are essential energy sources for the process industry. Insightful understanding of those molecules is useful to explore reactivities of coal and char. Therefore, coal and char molecular structures were investigated at atomic level using Materials Studio 7.0 software. Firstly, coal and char initial structures were constructed based on reported literatures. Secondly, those structures were improved by molecular mechanics, where functional group fragments were added to satisfy the property of coal or char. Then, the subsequent structures were optimized by annealing dynamics simulation to adjust density and elementary composition. Finally, the potential energies of coal and char were calculated using energy minimization method. It was pointed out that the estimated densities and elementary composition were agreements with the published literatures, which indicated that those structures were valid and reasonable. From the simulated results, it was shown that the Coulomb energy and van der Waals energy played a much more important role than other energies during the stabilizing molecular construction process. Thus, it was inferred that the weak bond was predominant in the thermal processing of coal or char. In addition, this work demonstrated that the molecular simulation technology was meaningful to construct the complex macromolecular structure.
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Key words:
- coal char /
- molecular simulation /
- molecular dynamics /
- annealing dynamics simulation
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Figure 4 Three-dimensional main body of coal before optimization (the meaning of gray, white, red, blue and yellow is C, H, O, N and S atom, respectively)
Figure 5 Functional group fragments of coal before optimization
(the meaning of gray, white, red, blue and yellow is C, H, O, N and S atom, respectively)
Figure 6 Three-dimensional main body of coal after optimization (the meaning of gray, white, red, blue and yellow is C, H, O, N and S atom, respectively)
Figure 7 Functional group fragments of coal after optimization
(the meaning of gray, white, red, blue and yellow is C, H, O, N and S atom, respectively)
Figure 8 Three-dimensional functional group fragments of char
(the meaning of gray, white, red, blue and yellow is C, H, O, N and S atom, respectively)
Figure 11 Coal density and volume variation with time
(a): relationships of density with simulation time; (b): relationships of volume with simulation time
Figure 12 Char density and volume variation with time
(a): relationships of density with simulation time; (b): relationships of volume with simulation time
Figure 13 Comparison of potential energies of coal molecular model
notes: Valence electron energy, EB is bond elastic energy; EA is bond angle energy; ET is torsion energy; EI is inverse energy; non bonding energy; EH is hydrogen bond energy; Evan is van der waals energy; EE is Coulomb energy
Figure 14 Comparison of potential energies of char molecular model
notes: Valence electron energy, EB is bond elastic energy, EA is bond angle energy; ET is torsion energy; EI is inverse energy; non bonding energy; EH is hydrogen bond energy; Evan is van der Waals energy; EE is Coulomb energy
Table 2 Molecule composition of coal molecular model
Table 3 Elements analysis of simulated coal and char
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