In the present study, we have conducted a fundamental study to understand the reasons for the deterioration by the pre-addition of catalysts such as Fe2O3 and CaCO3 to a coking coal, Goonyella. The addition of Fe2O3 resulted in the reductions in the maximum fluidity (log MF) and the drum index (DI), when the Fe2O3 of 0.31 μm were introduced to the coal. Of course the increase in the reactivity toward the solution-loss reaction was observed as previously reported. While in the case of the addition of CaCO3, no distinct changes in log MF, DI and CRI were observed irrespective of the size and the contents of CaCO3. The conversion of TI-PS (toluene insoluble and pyridine soluble) fraction to TS fraction was observed when the Fe2O3-added coal was heat-treated up to 440°C, while no changes were observed for the CaCO3-added coal. No signs of catalytic graphitization took place judged by X-ray diffraction study. The addition of Fe2O3 produced hollow balloon-like structure with 10 nm-thickness-amorphous carbon walls, while such formation was not observed for the case of CaCO3 addition. Finally, we concluded that the deterioration in the coke strength by the pre-addition of Fe2O3 is caused by the insufficient adhesion of coal particles due to the reduction of the TI-PS fraction as well as by the formation of the fragile balloon-like structures.
