THE USE OF MAGNETIC-RESONANCE PARAMETERS IN THE CHARACTERIZATION OF PREMIUM COALS AND OTHER COALS OF VARIOUS RANK

Eight premium coals and twelve Polish coals were investigated by means of e.s.r., 1H n.m.r., 13C CP-n.m.r. and dynamic nuclear polarization (DNP). The following parameters were studied: the concentration of free radicals, Ne; the 1H Zeeman relaxation rate, WZH; the 1H rotating-frame relaxation rate, WρH; the 1H DNP enhancement factor, PH; and the CP-determined carbon aromaticity, (fa)CP. The results generally agree with the patterns established in an earlier study of the same parameters of 60 other coals. The following relationships have been found between the above parameters and parameters obtained via proximate and ultimate analyses: Ne versus percentage volatile matter, WZH versus oxygen content, WρH versus Ne, PH versus carbon content and (fa)CP versus percentage volatile matter. For the premium coals it was observed that exposure to air prior to degassing resulted in irreversible changes in Ne, WZH and PH. © 1990.