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 recognized as the best approach to obtain quantitatively reliable aromaticity values and other skeletal parameters for coals, was applied to partly carbonized coal samples, a biomass char and the toluene-insolubles 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). Furthermore, in terms of accumulation times, the shorter C-13 T-1's of low-temperature chars makes SPE a more efficient technique than for coals. The higher concentrations of paramagnetic centres responsible for the shorter C-13 T-1's Still result in observability of 75% of the carbon in the chars by the SPE technique. The H/C ratios derived from the SPE measurements agree well with those obtained from elemental analysis. Copyright (C) 1996 Elsevier Science Ltd.