Nuclear magnetic resonance and ruthenium ion catalyzed oxidation reaction analysis for further development of aromatic ring size through the heat treatment of coking coals at >500 °C

The development of aromatic cluster size in heat-treated coals by heating above 500 °C is discussed. Heat treatment of coal was performed at 500, 600, and 700 °C to obtain semicoke samples. The temperature range was above the resolidification temperature of the coal samples. For comparison, a strongly coking coal, Australian Goonyella coal, and a slightly coking coal, Chinese Enshu coal, were used as the sample coals. Analysis of the virgin coals and the semicoke samples with solid-state ¹³C NMR indicated that the strongly coking coal tended to develop the aromatic ring size to a greater degree than the slightly coking coal as the heat-treatment temperature increased. To examine this tendency, a ruthenium ion catalyzed oxidation reaction was applied to the semicoke samples to obtain information concerning the distribution of the aromatic ring size. The products from this reaction also implied that the semicoke samples obtained from the strongly coking coal had an aromatic ring of larger size on average. A schematic representation of the behavior of molecules in the two coal samples during heating was established.