Abstract
Chemical structures of caking and non-caking coals were evaluated by solid state ^1H and ^<13>C-NMR. Semi cokes were prepared by heat treatments of the caking coals at temperatures ranging from 400 to 500℃ and also studied with the NMR measurements. Sizes of aromatic clusters of the samples were estimated based on the quantitative information on the distributions of carbon and hydrogen atoms assigned to several different chemical structures. It was found that the aromatic cluster size of the caking coal increased remarkably with increasing temperature from 400 to 500℃, where it undergoes softening and re-solidification. On-line gas analysis during pyrolysis revealed that almost no hydrogen gas was evolved from 400 to 500℃, though the growth of aromatic cluster could accompany hydrogen formation.
