Construction of bituminous coal vitrinite and inertinite molecular assisted by 13C NMR, FTIR and XPS

In order to study the structural properties of coal macerals in-depth, the proximate analysis, ultimate analysis, 13C solid nuclear magnetic resonance (13C NMR), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were employed to analyze the vitrinite and inertinite properties of Shanghaimiao bituminous coal. The results show that the vitrinite contains more hydrocarbon, nitrogen and sulfur elements than the inertinite while the inertinite contains more oxygen elements than the vitrinite. The 13C NMR results show that the vitrinite has more side chains of aliphatic hydrocarbons than the inertinite while the inertinite has more aromatic rings and more oxygen-aliphatic structures than the vitrinite. The FTIR results show that the contents of alcohol hydroxyl, phenol hydroxyl and ether in the vitrinite is similar to that in the inertinite. However, the inertinite contains more carboxyl groups than the vitrinite. The XPS results show that the nitrogen element is mostly in the form of pyridine, and the sulfur element is mostly in the form of mercaptan and sulfoether in the coal. Based on the above-mentioned analysis, we constructed the molecular structure models of the vitrinite and inertinite. The molecular formula of vitrinite is C126H99O12N3S2 while the molecular formula of inertinite is C131H98O17.