Speciation of heteroatoms in coal by sulfur- and nitrogen-selective techniques

The peroxyacetic acid oxidation products from a series of coals of organic sulfur content 0.5-9.8 wt% were examined. The distributions of organic S and N compounds were determined by gas chromatography with sulfur-selective flame photometric and nitrogen-selective thermionic specific detection respectively. A selected sample was also examined in greater detail using low-voltage high-resolution mass spectrometry. The distribution of organic sulfur compounds in the oxidation products was remarkably similar for all the coals. The number of sulfur compounds detected was small compared with that of organic nitrogen compounds detected. This suggests that the sulfur chemistry of coal is considerably simpler than its nitrogen chemistry. Analysis of the m.s. data, together with a comparison of sulfur-selective and nitrogen-selective chromatograms, indicated that a significant proportion of the heteroatomic species present in coal contain more than one heteroatom. This is significant, because few models of coal structure incorporate such species.