Revealing the selective catalysis effect of trace metal components in Zhundong coal during coal conversion to solid carbon under inert and active atmosphere

Conversion of Zhundong coal to solid carbon materials is a high-value route for thermochemical utilization of large-reserve Zhundong coal, in which carbonization and activation are two essential processes. Trace metal components existed in Zhundong coal have been found to be key factors regulating coal thermochemical conversion process. However, their specific roles in carbonization and activation under various thermochemical condition are still unclear. In this work, we elucidated selective catalysis effects of trace metal components on the conversion of coal to solid carbon under inert and active atmosphere. Based on the crystalline characterizations of carbonized raw coal and demineralized coal under inert atmosphere, we found that inherent metal components efficiently catalyze the growth of graphitic microcrystalline and thereby improve the structural stability of carbon materials. Porous structure characterizations and kinetic analyses on activation of raw and demineralized coal also showed that the existed trace metal can catalyze etching reactions between carbonaceous skeleton and activation agent, and thus facilitate the development of hierarchical porous structure. Control experiments based on model sample individually loaded with typical metal component further demonstrated that the observed selective catalysis effects under inert and active atmosphere are ascribed to trace Fe and Ca, respectively. Above elucidated selective catalysis effect under different thermochemical conversion process provides new insights into adjusting porous and crystalline structures of coal-based carbon materials to meet varying requirements in different application scenarios.