Synergistic effect between coal and iron-based waste catalyst containing wax from Fisher-Tropsch synthesis during their co-pyrolysis

The iron-based waste catalysts (IWC) from Fisher-Tropsch synthesis, as a kind of waste containing abundant hydrocarbons and iron species, can be treated by the co-pyrolysis technology to realize the clean, efficient utilization of waste and coal. In this study, the synergistic effect and co-pyrolysis characteristics of IWCs and a bituminous coal were investigated by TG-MS and Py-GCMS. The results show that the co-pyrolysis of IWCs and coal occurs primarily in the range of 200-500 degrees C. The tar composition from the co-pyrolysis of coal and IWC1 composed of paraffins is mainly aliphatic acids and olefins, while the co-pyrolysis of coal and IWC2 with higher content of mineral matters principally yields aromatics and phenols. The strength of synergistic effect between coal and IWCs is enhanced by the increasing mass ratio of IWCs to coal and affected by the co-pyrolysis temperature, but the effects of temperature in the range of 200-400 degrees C and 400-500 degrees C are almost opposite. These changes of strength are related to the content of paraffins and iron species in IWCs, promoting or limiting the release of volatiles and changing the content of tar components, especially the content of aliphatic acids. The gas composition is also affected by the interaction. This study provides a basis for the further clean co-utilization of iron based waste catalysts from FT synthesis process and coal.