Thermogravimetry-photoionization mass spectrometry of different rank coals

Volatile matter evolved during pyrolysis of 20 different rank coals was stu died by thermogravimetry-photoionization mass spectrometry (TG-PI-MS). The composition of the TGA effluent revealed several significant trends with co al rank. First, the relative intensities of peaks due to compounds containi ng oxygen such as CnH2nO (n = 2, 3, or 4), phenols, and dihydroxybenzenes d ecreased with increasing coal rank. Also, the relative intensities of peaks due to aromatic compounds such as naphthalenes, phenanthrenes, and pyrenes increased with increasing coal rank. Mass signals due to sulfur compounds evolved from-coal showed qualitative correlations between CS2 (%TIC) and py ritic sulfur content and between CH3SH (%TIC) and aliphatic sulfur content. Several of the coals were extracted with a solvent to remove the soluble p ortion of the coal. TG-PI-MS analysis of the raw coal, extracted material a nd coal residue remaining after solvent extraction produced very similar ma ss spectral These results suggest that the majority of the compounds observ ed by TG-PI-MS are products: of thermal cleavage of bonds within the coal s tructure. This conclusion is further supported by 337 nm laser desorption m ass spectrometry of the solvent extracts, The results from these analyses s uggest that volatile matter, like coal itself, consists of compounds with a range of molecular weights but with similar molecular structures.