EFFECT OF PREHEATING IN CARBONIZATION ON THE NATURE OF RESULTANT COALTARS AND PITCHES

The tars and resultant pitches produced by normal (wet) and preheated carbonization of a high-volatile bituminous coal in a semi-industrial scale coke oven have been compared using a combination of liquid chrom atographic (LC) and nuclear magnetic resonance (NMR) spectroscopic met hods. The toluene-soluble (TS) and quinoline- (QI) and toluene-insolub le (TI) fractions were selected to assess the differences in compositi on. HPLC revealed that preheating gave rise to tars containing lower p roportions of substituted polynuclear aromatic compounds (PACs) than t hose produced from the wet coal charge. Pitches derived from the tars obtained with preheating contain more higher molecular weight species as reflected in the higher QI, TI, and asphaltene contents, together w ith a higher proportion of peri-condensed PACs in the TS fractions. Si milarly, solid state C-13 NMR has indicated that the QI and TI fractio ns from the pitches obtained from the preheated charges contain more h ighly condensed aromatic structures; limitations with cross polarizati on (CP) can be largely overcome using the single pulse excitation (SPE ) technique.