The functionality of nitrogen in coal and derived liquids: An XPS study

High molecular mass fractions considerably enriched in nitrogen compounds were obtained from coal-derived asphaltenes by means of a chemical separation scheme. X-ray photoelectron spectroscopy was used to determine the nitrogen functionality of samples before and after processing. It was found that the nitrogen species are predominantly pyrrole and pyridine types, with evidence of bifunctionality. Comparison with XPS spectra of the original coal and with a pyrolysis tar before hydrotreatment suggests that there was no significant change in the distribution of nitrogen functional groups in high molecular mass fractions after processing.