Time-resolved Curie-point pyrolysis mass spectrometry (Py-MS) is demonstrated to be a promising new method for studying thermal decomposition reactions in coal. The effect of low-temperature oxidation (“weathering”) on the structural characteristics of a high-volatile bituminous Hiawatha coal was investigated. Microgram amounts of coal were heated to 610 °C at a rate of 102K/s. As many as 40 low-voltage mass spectra were obtained within 8 s and subsequently evaluated by means of factor analysis. The results were compared with those of conventional time-integrated Curie-point Py-MS as well as combined thermogravimetry/mass spectrometry. It was found that the decomposition of Hiawatha coal takes place in several stages while the samples are heated up to 610 °C. The evaporation of “trapped” compounds and the decomposition of labile functional groups around 300 °C represent the first steps followed by the rapid decomposition of the bulk components around 550 °C and, finally, the continued slow decomposition of the char residue. The weathered coal sample has undergone substantial changes as reflected by the pyrolysis results. The amount of “trapped” volatile components (primarily alkylnaphthalenes) is markedly decreased in the weathered coal and is accompanied by a decrease in the abundance of hydroxy aromatic compound series (primarily alkylphenols). Furthermore, the yield of short-chain aliphatic carboxylic and carbonylic moieties is strongly increased.
ASJC Scopus subject areas
- Chemical Engineering(all)
- Fuel Technology
- Energy Engineering and Power Technology