SOLID-STATE C-13 NMR-STUDY OF CHINESE COALS

Ten coals of different metamorphic degree have been investigated by th e use of C-13 CP/MAS NMR technique, of which the spin-lattice relaxati on, variable contact time and dipolar dephasing experiments were perfo rmed on each coal. The data from above experiments, together with norm al CP/MAS integration over selected chemical shift ranges, were used t o derive 12 parameters of carbon skeletal structure including the arom aticity. These parameters are correlated with carbon content(weight pe r cent) in coal and we find that there are close relations between the NMR parameters and metamorphic degree of coals. From the ratio of aro matic bridgehead to aromatic peripheral carbons as measured by NMR, th e aromatic cluster size may be estimated for each coal.