The variation of structural characteristics of macerals during pyrolysis☆

Vitrinite and inertinite were separated by DGC from Chinese Shenmu bituminous coal and the structural characteristics of the macerals, before and after pyrolysis, were analyzed by ultimate analysis, FTIR and 13C NMR. The results showed that vitrinite chars always had higher H and lower C content than inertinite char at the same pyrolysis temperature. The FTIR and 13C NMR indicated that vitrinite had more aliphatic C–H, hydrogen bonding and lower aromaticity. With increasing temperature, the aliphatic C–H decreased, aromatic C–H, aromaticity and Har/Hal ratio increased. At the same temperature, inertinite always had higher Har/Hal ratio than vitrinite, which is consistent with that inertinite had higher aromaticity than vitrinite. And the Har/Hal ratio was also related to the remainder volatile matter. With increasing Har/Hal ratio, the remainder volatile matter in vitrinite and inertinite decreased. The higher aromaticity and Har/Hal ratio and lower H content of the inertinite in all temperature range were correlated with its higher thermal stability and lower volatile yield than vitrinite.