Comprehensive Thermogravimetric and Pyrolysis-GCMS Characterization of Thirteen Indian Coals Across Low to High Rank

India’s vast coal reserves exhibit wide variability in coal structure and composition, yet systematic insights into their rank-dependent thermal behavior remain limited. Understanding these variations is critical for improving cleaner utilization pathways and value-added carbon material development. Thirteen Indian coals ranging from lignite to semi-anthracite were characterized using thermogravimetric/differential thermogravimetric (TG/DTG) analysis and pyrolysis – GC/MS (Py-GC/MS) to elucidate structure – reactivity relationships. TG/DTG mass-loss profiles were deconvoluted into six Gaussian sub-peaks representing distinct decomposition events. Peak temperatures (Tp) increased with mean vitrinite reflectance (R0), reflecting enhanced structural stability with coalification. The dominant devolatilization peak (aliphatic C – C/C – H processes) contributed ≈34–40% across all ranks, while high-temperature aromatic condensation increased from ≈4–7% in low ranks to ≈12–15.5% in high ranks. Py-GC/MS revealed a compositional shift in volatiles from oxygenated and aliphatic species toward condensed aromatics, with n-alkenes decreasing from ≈37% to ≈15% and triaromatics rising from ≈0–3% to ≈16–17%. These integrated findings establish a coherent framework for understanding rank-dependent reactivity of Indian coals, supporting optimized thermal conversion strategies and the sustainable utilization of indigenous carbon resources.