The pentane- and toluene-soluble fractions of a petroleum residue and three coal tars by size exclusion chromatography and UV-fluorescence spectroscopy

A petroleum atmospheric pressure distillate residue and three tars derived from different coals using different seventies of thermal treatment were separated into 7 fractions using column chromatography on silica and sequential elution by the solvent sequence pentane, toluene, acetonitnile, pyridine, 1-methyl-2-pyrrolidinone (NMP), and water. The fractions from the four extractions were compared using size exclusion chromatography (SEC) in NMP as eluent and by synchronous UV-fluorescence (UV-F). SEC results showed that the size of the aromatic molecules increased from the first pentane soluble fractions to the toluene-soluble fractions, with the petroleum residue fractions of larger size than the equivalent fractions from coal liquids. The three coal tars showed significant differences, indicating that temperature of pyrolysis had a significant effect on the molecular size. Synchronous UV-F spectra of the four sets of fractions, in solution in NMP, again showed significant differences between the petroleum residue and the coal tars, as well as amongst the three coal tars.