PYRIDINE EXTRACTS OF SOLID FUELS

Pyridine extracts of a coking coal and of two lignites have been further separated and the 1H and 13C n.m.r. spectra of the various fractions have been recorded. Three methods of separation were investigated: gel-permeation chromatography, successive extraction with petroleum ether and with benzene as used by previous workers for supercritical-gas extracts, and the classical extraction of the fractions. Gel-permeation chromatography gave most promise of effective separation but the fractions obtained often contained too little material to give n.m.r. spectra. The n.m.r. spectra of the chloroform-soluble material from the pyridine extracts of the coking coal were consistent with a material consisting of polynuclear aromatic nuclei joined through simple bridge structures and possibly also through direct carbon-carbon linkages. The nuclei were substituted by branched and unbranched paraffin chains, some of which were 7 or 8 carbon atoms long. It is probable that alicyclic structures were also present. The aromatic nuclei were mobile in solution. 60% of the carbon atoms were aromatic, and it can therefore be calculated that the molecular weight per aromatic nucleus was 200-300. It is suggested that 13C n.m.r. spectra may be used to characterize chemicals likely to confer coking properties on solid fuels. © 1979.