QUANTITATIVE SOLID-STATE C-13 NMR MEASUREMENTS ON COKES, CHARS AND COAL-TAR PITCH FRACTIONS

Bloch decay or single pulse excitation (SPE) C-13 n.m.r., generally re cognized as the best approach to obtain quantitatively reliable aromat icity values and other skeletal parameters for coals, was applied to p artly carbonized coal samples, a biomass char and the toluene-insolubl es from a coal tar and a corresponding pitch. As found previously for coals, the aromaticities and non-protonated carbon concentrations were generally higher than those estimated by cross-polarization (CP). Fur thermore, in terms of accumulation times, the shorter C-13 T-1's of lo w-temperature chars makes SPE a more efficient technique than for coal s. The higher concentrations of paramagnetic centres responsible for t he shorter C-13 T-1's Still result in observability of 75% of the carb on in the chars by the SPE technique. The H/C ratios derived from the SPE measurements agree well with those obtained from elemental analysi s. Copyright (C) 1996 Elsevier Science Ltd.