Molecular Modeling and Reactivity of Thermally Altered Coals by Molecular Simulation Techniques

Abstract

In this study, the chemical structure characteristics and reactivity features of three thermally altered coals with different ranks were analyzed by combining molecular modeling and molecular simulation methods to reveal and predict their chemical behaviors and properties. First, 2D molecular models of the three thermally altered coals were constructed based on X-ray photoelectron spectroscopy (XPS), solid-state 13 C nuclear magnetic resonance spectroscopy ( 13 C NMR), high-resolution transmission electron microscopy (HRTEM), and ultimate analysis data. 2D molecular models of the three thermally altered coals show different structural characteristics. 3D molecular models of the three thermally altered coals and their potential energy distributions were obtained by geometry optimization and anneal dynamics simulations. For exploring the reactivity of the three thermally altered coals with different ranks, the frontier molecular orbitals and Mulliken bond orders of the three molecular models were calculated based on quantum chemistry calculations. The frontier orbital (HOMO and LUMO) analysis results indicated that compared with the other two thermally altered coals, the thermally altered coal with R o of 8.32% had higher reactivity in electrophilic or nucleophilic reactions. The bond order results provided detailed information on the active sites of the three thermally altered coal molecules, thereby predicting the thermal behaviors of the three thermally altered coals. These works can provide a theoretical basis for the industrial utilization of thermally altered coal. Meanwhile, these three models will be used in the future to study the combustion, pyrolysis, and graphitization mechanisms of thermally altered coals by reactive molecular dynamics methods.

Study on Molecular Model Construction and Gas Adsorption Simulation of Anthracite in the Qinshui Basin

“…According to the research findings from the 13 C NMR experiment, the X BP of CZ anthracite is 0.34. Since X BP values of benzene, naphthalene, anthracene, pyrene, and fluorene are 0, 0.25, 0.4, 0.5, and 0.57, respectively, it can be inferred that the constructed macromolecular structure is mainly composed of naphthalene and anthracene . Besides, the C content is 90.82%.…”

“…Since X BP values of benzene, naphthalene, anthracene, pyrene, and fluorene are 0, 0.25, 0.4, 0.5, and 0.57, respectively, it can be inferred that the constructed macromolecular structure is mainly composed of naphthalene and anthracene. 35 Besides, the C content is 90.82%. Research shows that when the C content in a coal sample is about 90%, the average number of benzene rings in a condensed aromatic ring in the molecular structure is 3−5.…”

Construction and verification of vitrinite-rich and inertinite-rich Zhundong coal models at the aggregate level: new insights from the spatial arrangement and thermal behavior perspective

“…The simulation detail is that the smart algorithm method, Q eq charge equilibration method, Dreiding force led, Ewald for the electrostatic and atom based for van der Waals with 12.5 Å cutoff distance were used in the geometric optimization, box-construction and annealing procedure, respectively. 50,51 The optimized box with six optimized molecules were rst annealed in NPT ensemble from 300 to 500 K with NHL thermostat. And then, the NVT annealing was performed on the annealed NPT structure with the lowest total potential energy, using NHL thermostat from 300 to 500 K in 300 ps.…”

Occurrence Modes of Critical Metals (Li+ and Ge4+) in the Organic Molecular Structures of Coal: A Density Functional Theory Study

“…The electronegative region on the surface of organic molecular structures exhibited a strong adsorption capacity for critical metals. The molecular orbital theory was also crucial to analyze the chemical reactions of molecular systems because electrons in front orbitals were usually more active . It was simple to cause electron transfer, bond formation, or bond breakage, leading to a reaction .…”

“…The molecular orbital theory was also crucial to analyze the chemical reactions of molecular systems because electrons in front orbitals were usually more active. 53 It was simple to cause electron transfer, bond formation, or bond breakage, leading to a reaction. 54 The atoms with the highest negative Mulliken charge in organic molecular structures coordinated best with the critical metals.…”