Unveils the macromolecular structure of high-sulfur Indian coal for hydrogen production

In this study, for the first time, we reported the molecular structure of Cenozoic coal from the northeastern region of India, which is a rare form of coal and known as low quality due to high sulfur, non-coking nature, low ash fusion temperature, and high volatile matter. These findings are crucial for efficiently utilizing this coal in hydrogen production. The analysis revealed that the coal has a high aromaticity (77.33 %) and aliphatic structure (22.66 %), with a molecular formula of C₁₇₉H₁₄₀O₃₂N₃S₄. The bridge to peripheral aromatic carbon ratio is 0.657, indicating the prevalence of tetracyclic pyrene as the primary aromatic skeleton, along with auxiliary structural units such as pentacene, chrysene, anthracene, naphthalene, and benzene. The coal contains oxygen-containing functional groups and structures such as pyridine, pyrrolic, thiophenol, and thiophene. The study also included creating and optimizing 2D and 3D coal macromolecular structures through molecular dynamics simulations and global hybrid density functional theory. Additionally, the thermal properties and model free kinetic study of the coal were investigated, showing an ignition temperature of 416 °C and an apparent activation energy of 171.36 kJ mol⁻¹, providing insight into its degradation behaviour at different temperatures.