Studies on the Chemical Structural Change during Carbonization Process

In order to investigate a relationship between chemical structure of coking coals and their thermoplasticity during their carbonizationn, evaluation of both hydrogen transfer reaction and heat treatment coupled with SEM observation was conducted along with measurement of SPE/MAS 13C NMR of virgin coals. The hydrogen transfer reaction from coal to hydrogen acceptor was carried out at 420 °C for 5 min. In the case using anthracene as acceptor, 0.6−1.1 mg of H2 was transferred from 1 g of daf coal to the acceptor. A correlation between the weight of hydrogen transferred and % carbon of each coal (coal rank) showed a similar tendency to that between Gieseler fluidity and coal rank. This result suggests that the quantities of donatable hydrogen could be correlated strongly with the development of plasticity. To obtain the insight into the amounts of functional groups involved in releasing hydrogen, solid state 13C NMR of sample coals was measured, the results indicating the presence of somewhat correlation between the concentrations of bridge methylene groups linking two aromatic moieties and maximum fluidities. Heat treatment of the coals up to their softening temperature, resolidification temperature, and 1000 °C was also conducted, the combination of crystallite parameters of the resulting chars and their SEM observation suggesting that lamellar structures of coal became disordered upon heating and then turned to the ordered structures as the heating proceeds. On the basis of the above results, chemical structural changes during carbonization process are discussed.