Abstract
To compare the differences in chemical structure between vitrinite and inertinite and their effects on transformation and utilization, this paper separated vitrinite and inertinite from three parent coal samples (high-volatile bituminous coal (R(max) (%) = 0.65), medium-volatile bituminous coal (R(max) (%) = 1.25), and low-volatile bituminous coal (R(max) (%) = 1.7)), and the differences in chemical structure were analyzed from three aspects: aromatic structure, aliphatic structure, and cross-linking structure. The molecular structure model of a single maceral was constructed, and the chemical bond parameters and the impact on coal conversion and utilization were analyzed. The results showed that (i) in the same sample, inertinite has advanced evolution characteristics, higher aromaticity, and ring condensation degree, but vitrinite has a faster evolution rate than inertinite. (ii) The molecular structure model shows that with the increase of the evolution degree of samples, the proportion of polycyclic aromatic hydrocarbons increased gradually. After molecular dynamics simulations, the cross-linked structures in the planar macromolecular structure have huge torsion deformation, and the torsion of aromatic structure decreased from benzene, naphthalene, anthracene, and phenanthrene. (iii) The analysis of chemical bond parameters showed that the ether-oxygen bond with shorter bond length and higher bond energy is a key factor hindering the breakage recombination of the macromolecular structure. In the high-evolution stage, the ether carbon content in inertinite is higher than that in vitrinite and has a stronger cross-linking structure. Therefore, it is less reactive in the transformation processes of coking and gasification. However, inertinite has larger aromatic layers and a more ordered orientation, which has certain advantages in the preparation of coal-based graphite.