Coal gangue shows promise as a potential raw material for coal pyrolysis catalysts. This study prepared coal gangue char catalysts from two types of coal gangue (CGY and CGH) via pyrolysis at 700 °C under N2, O2/N2 and steam/N2 atmospheres, labeled as CGY-N, CGY-ON, CGY-SN and CGH-N, CGH-ON, CGH-SN, respectively. Their catalytic performance in tar-rich coal pyrolysis was evaluated using a thermogravimetric analyzer and a fixed-bed reactor. Results showed that reactive atmosphere-derived char catalysts promoted coal weight loss, with CGY-SN and CGH-SN increasing weight loss of coal pyrolysis at 600 °C from 20.51 wt% to 22.05 wt% and 22.50 wt%, respectively. These catalysts generally reduced tar yield while increasing semicoke and water yields. They also decreased monocyclic aromatic hydrocarbons and enriched polycyclic aromatic hydrocarbons in the tar, alongside promoting the production of CH4, H2 and CO. Furthermore, they enhanced the gasification reactivity of the resulting semicoke. CGY-ON demonstrated particularly high activity, which is likely associated with its richness in K-, Ca- and Fe-bearing minerals, coupled with the exposure of active sites resulting from organic matter consumption under the O2/N2 atmosphere. An exception was CGH-N and CGH-SN, which increased monocyclic aromatic hydrocarbons from 25.67% to 30.65% and 31.64%, possibly related to shape-selective catalysis in the newly formed micropores. These insights provide a preliminary basis for the development of efficient coal gangue-based catalysts for tar-rich coal pyrolysis.
Chang et al. (Wed,) studied this question.