PYROLYSIS FIELD-IONIZATION MASS-SPECTROMETRY OF EXTRACTS SEPARATED FROM A GAS COAL AND ITS MACERALS USING N-METHYL-2-PYRROLIDINONE

The characterization by pyrolysis-field ionization mass spectrometry (Py-FIMS) of the N-methyl-2-pyrrolidinone (NMP) extracts of several coals (gas coal, flame coal, orthocoking coal) has recently been described. This study is now extended to the NMP extracts of the macerals, i.e., vitrinite, exinite, and inertinite, after separation from the gas coal sample. The Py-FI mass spectrum of the original gas coal is also reported. The contribution of each maceral to the extractible phase was estimated from the petrographic analysis and from the yields of NMP extraction. The thermogram patterns are characteristic for each maceral extract. A great similarity was observed between vitrinite (the main maceral) and the parental coal extracts. In this case the two maxima displayed by the thermograms have approximately the same area. Conversely, the exinite and inertinite groups are mainly retained in the extraction residues. Their thermograms are strikingly different from the one of vitrinite. The extractible phases, obtained in low yields, as mostly made of easily distillable components. All the three macerals contribute to the formation of hydroxylated compounds in the high-temperature devolatilization step. No major distinction between the aromatic structures of the maceral and the parental coal extracts can be evidenced.